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“Control of proton transport and hydrogenation in double-gated graphene”. Tong J, Fu Y, Domaretskiy D, Della Pia F, Dagar P, Powell L, Bahamon D, Huang S, Xin B, Costa Filho RN, Vega LF, Grigorieva IV, Peeters FM, Michaelides A, Lozada-Hidalgo M, Nature 630, 619 (2024). http://doi.org/10.1038/s41586-024-07435-8
Abstract: The basal plane of graphene can function as a selective barrier that is permeable to protons but impermeable to all ions and gases, stimulating its use in applications such as membranes, catalysis and isotope separation. Protons can chemically adsorb on graphene and hydrogenate it, inducing a conductor–insulator transition that has been explored intensively in graphene electronic devices. However, both processes face energy barriersand various strategies have been proposed to accelerate proton transport, for example by introducing vacancies, incorporating catalytic metalsor chemically functionalizing the lattice. But these techniques can compromise other properties, such as ion selectivity or mechanical stability. Here we show that independent control of the electric field,<italic>E</italic>, at around 1 V nm<sup>−1</sup>, and charge-carrier density,<italic>n</italic>, at around 1 × 10<sup>14</sup> cm<sup>−2</sup>, in double-gated graphene allows the decoupling of proton transport from lattice hydrogenation and can thereby accelerate proton transport such that it approaches the limiting electrolyte current for our devices. Proton transport and hydrogenation can be driven selectively with precision and robustness, enabling proton-based logic and memory graphene devices that have on–off ratios spanning orders of magnitude. Our results show that field effects can accelerate and decouple electrochemical processes in double-gated 2D crystals and demonstrate the possibility of mapping such processes as a function of<italic>E</italic>and<italic>n</italic>, which is a new technique for the study of 2D electrode–electrolyte interfaces.
Keywords: A1 Journal Article; Condensed Matter Theory (CMT) ;
Impact Factor: 64.8
DOI: 10.1038/s41586-024-07435-8
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“Comment on “Misinterpretation of the Shuttleworth equation””. Faraji F, Neyts EC, Milošević, MV, Peeters FM, Scripta Materialia 250, 116186 (2024). http://doi.org/10.1016/j.scriptamat.2024.116186
Keywords: A1 Journal Article; CMT
Impact Factor: 6
DOI: 10.1016/j.scriptamat.2024.116186
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“Spin-orbit torque vector quantification in nanoscale magnetic tunnel junctions”. Sethu KKV, Yasin F, Swerts J, Sorée B, De Boeck J, Kar GS, Garello K, Couet S, ACS nano 18, 13506 (2024). http://doi.org/10.1021/ACSNANO.3C11289
Abstract: Spin-orbit torques (SOT) allow ultrafast, energy-efficient toggling of magnetization state by an in-plane charge current for applications such as magnetic random-access memory (SOT-MRAM). Tailoring the SOT vector comprising of antidamping (T-AD) and fieldlike (T-FL) torques could lead to faster, more reliable, and low-power SOT-MRAM. Here, we establish a method to quantify the longitudinal (T-AD) and transverse (T-FL) components of the SOT vector and its efficiency chi(AD) and chi(FL), respectively, in nanoscale three-terminal SOT magnetic tunnel junctions (SOT-MTJ). Modulation of nucleation or switching field (B-SF) for magnetization reversal by SOT effective fields (B-SOT) leads to the modification of SOT-MTJ hysteresis loop behavior from which chi(AD) and chi(FL) are quantified. Surprisingly, in nanoscale W/CoFeB SOT-MTJ, we find chi(FL) to be (i) twice as large as chi(AD) and (ii) 6 times as large as chi(FL) in micrometer-sized W/CoFeB Hall-bar devices. Our quantification is supported by micromagnetic and macrospin simulations which reproduce experimental SOT-MTJ Stoner-Wohlfarth astroid behavior only for chi(FL) > chi(AD). Additionally, from the threshold current for current-induced magnetization switching with a transverse magnetic field, we show that in SOT-MTJ, T-FL plays a more prominent role in magnetization dynamics than T-AD. Due to SOT-MRAM geometry and nanodimensionality, the potential role of nonlocal spin Hall spin current accumulated adjacent to the SOT-MTJ in the mediation of T-FL and chi(FL) amplification merits to be explored.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 17.1
DOI: 10.1021/ACSNANO.3C11289
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“Capillary Condensation of Water in Graphene Nanocapillaries”. Faraji F, Neyts EC, Milošević, MV, Peeters FM, Nano Letters 24, 5625 (2024). http://doi.org/10.1021/acs.nanolett.4c01088
Abstract: Recent experiments have revealed that the macroscopic Kelvin equation remains surprisingly accurate even for nanoscale capillaries. This phenomenon was so far explained by the oscillatory behavior of the solid−liquid interfacial free energy. We here demonstrate thermodynamic and capillarity inconsistencies with this explanation. After revising the Kelvin equation, we ascribe its validity at nanoscale confinement to the effect of disjoining pressure.
To substantiate our hypothesis, we employed molecular dynamics simulations to evaluate interfacial heat transfer and wetting properties. Our assessments unveil a breakdown in a previously established proportionality between the work of adhesion and the Kapitza conductance at capillary heights below 1.3 nm, where the dominance of the work of adhesion shifts primarily from energy to entropy. Alternatively, the peak density of the initial water layer can effectively probe the work of adhesion. Unlike under bulk conditions, high confinement renders the work of adhesion entropically unfavorable.
Keywords: A1 Journal Article; CMT
Impact Factor: 10.8
DOI: 10.1021/acs.nanolett.4c01088
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“Floquet engineering of axion and high-Chern number phases in a topological insulator under illumination”. Shafiei M, Fazileh F, Peeters FM, Milošević, MV, SciPost Physics Core 7, 024 (2024). http://doi.org/10.21468/SCIPOSTPHYSCORE.7.2.024
Abstract: Quantum anomalous Hall, high-Chern number, and axion phases in topological insulators are characterized by its Chern invariant C (respectively, C = 1, integer C > 1, and C = 0 with half-quantized Hall conductance of opposite signs on top and bottom surfaces). They are of recent interest because of novel fundamental physics and prospective applications, but identifying and controlling these phases has been challenging in practice. Here we show that these states can be created and switched between in thin films of Bi2Se3 by Floquet engineering, using irradiation by circularly polarized light. We present the calculated phase diagrams of encountered topological phases in Bi2Se3, as a function of wavelength and amplitude of light, as well as sample thickness, after properly taking into account the penetration depth of light and the variation of the gap in the surface states. These findings open pathways towards energy-efficient optoelectronics, advanced sensing, quantum information processing and metrology.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.21468/SCIPOSTPHYSCORE.7.2.024
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“Interlink between Abnormal Water Imbibition in Hydrophilic and Rapid Flow in Hydrophobic Nanochannels”. Zhou R, Neek-Amal M, Peeters FM, Bai B, Sun C, Physical Review Letters 132, 184001 (2024). http://doi.org/10.1103/PhysRevLett.132.184001
Abstract: Nanoscale extension and refinement of the Lucas-Washburn model is presented with a detailed analysis of recent experimental data and extensive molecular dynamics simulations to investigate rapid water flow and water imbibition within nanocapillaries. Through a comparative analysis of capillary rise in hydrophilic nanochannels, an unexpected reversal of the anticipated trend, with an abnormal peak, of imbibition length below the size of 3 nm was discovered in hydrophilic nanochannels, surprisingly sharing the same physical origin as the well-known peak observed in flow rate within hydrophobic nanochannels. The extended imbibition model is applicable across diverse spatiotemporal scales and validated against simulation results and existing experimental data for both hydrophilic and hydrophobic
Keywords: A1 Journal Article; CMT
Impact Factor: 8.6
Times cited: 1
DOI: 10.1103/PhysRevLett.132.184001
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“Two new members of the covalent organic frameworks family : crystalline 2D-oxocarbon and 3D-borocarbon structures”. Hassani N, Movafegh-Ghadirli A, Mahdavifar Z, Peeters FM, Neek-Amal M, Computational materials science 241, 1 (2024). http://doi.org/10.1016/J.COMMATSCI.2024.113022
Abstract: Oxocarbons, known for over two centuries, have recently revealed a long-awaited facet: two-dimensional crystalline structures. Employing an intelligent global optimization algorithm (IGOA) alongside densityfunctional calculations, we unearthed a quasi -flat oxocarbon (C 6 0 6 ), featuring an oxygen -decorated hole, and a novel 3D-borocarbon. Comparative analyses with recently synthesized isostructures, such as 2D -porous carbon nitride (C 6 N 6 ) and 2D -porous boroxine (B 6 0 6 ), highlight the unique attributes of these compounds. All structures share a common stoichiometry of X 6 Y 6 (which we call COF-66), where X = B, C, and Y = B, N, O (with X not equal Y), exhibiting a 2D -crystalline structure, except for borocarbon C 6 B 6 , which forms a 3D crystal. In our comprehensive study, we conducted a detailed exploration of the electronic structure of X 6 Y 6 compounds, scrutinizing their thermodynamic properties and systematically evaluating phonon stability criteria. With expansive surface areas, diverse pore sizes, biocompatibility, pi-conjugation, and distinctive photoelectric properties, these structures, belonging to the covalent organic framework (COF) family, present enticing prospects for fundamental research and hold potential for biosensing applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.3
DOI: 10.1016/J.COMMATSCI.2024.113022
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“Goodenough-Kanamori-Anderson high-temperature ferromagnetism in tetragonal transition-metal xenes”. Yorulmaz U, Šabani D, Sevik C, Milošević, MV, 2D materials 11, 035013 (2024). http://doi.org/10.1088/2053-1583/AD3E08
Abstract: Seminal Goodenough-Kanamori-Anderson (GKA) rules provide an inceptive understanding of the superexchange interaction of two magnetic metal ions bridged with an anion, and suggest fostered ferromagnetic interaction for orthogonal bridging bonds. However, there are no examples of two-dimensional (2D) materials with structure that optimizes the GKA arguments towards enhanced ferromagnetism and its critical temperature. Here we reveal that an ideally planar GKA ferromagnetism is indeed stable in selected tetragonal transition-metal xenes (tTMXs), with Curie temperature above 300 K found in CrC and MnC. We provide the general orbitally-resolved analysis of magnetic interactions that supports the claims and sheds light at the mechanisms dominating the magnetic exchange process in these structures. Furthermore, we propose the set of three GKA-like rules that will guarantee room temperature ferromagetnism. With recent advent of epitaxially-grown tetragonal 2D materials, our findings earmark tTMXs for facilitated spintronic and magnonic applications, or as a desirable magnetic constituent of functional 2D heterostructures.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 5.5
DOI: 10.1088/2053-1583/AD3E08
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“Unconventional superconducting diode effects via antisymmetry and antisymmetry breaking”. Li C, Lyu Y-Y, Yue W-C, Huang P, Li H, Li T, Wang C-G, Yuan Z, Dong Y, Ma X, Tu X, Tao T, Dong S, He L, Jia X, Sun G, Kang L, Wang H, Peeters FM, Milošević, MV, Wu P, Wang Y-L, Nano letters 24, 4108 (2024). http://doi.org/10.1021/ACS.NANOLETT.3C05008
Abstract: Symmetry breaking plays a pivotal role in unlocking intriguing properties and functionalities in material systems. For example, the breaking of spatial and temporal symmetries leads to a fascinating phenomenon: the superconducting diode effect. However, generating and precisely controlling the superconducting diode effect pose significant challenges. Here, we take a novel route with the deliberate manipulation of magnetic charge potentials to realize unconventional superconducting flux-quantum diode effects. We achieve this through suitably tailored nanoengineered arrays of nanobar magnets on top of a superconducting thin film. We demonstrate the vital roles of inversion antisymmetry and its breaking in evoking unconventional superconducting effects, namely a magnetically symmetric diode effect and an odd-parity magnetotransport effect. These effects are nonvolatilely controllable through in situ magnetization switching of the nanobar magnets. Our findings promote the use of antisymmetry (breaking) for initiating unconventional superconducting properties, paving the way for exciting prospects and innovative functionalities in superconducting electronics.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 10.8
DOI: 10.1021/ACS.NANOLETT.3C05008
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“Effects of intralayer correlations on electron-hole double-layer superfluidity”. Pascucci F, Conti S, Perali A, Tempère J, Neilson D, Physical review B 109, 094512 (2024). http://doi.org/10.1103/PHYSREVB.109.094512
Abstract: We investigate the intralayer correlations acting within the layers in a superfluid system of electron -hole spatially separated layers. In this system, superfluidity is predicted to be almost exclusively confined to the Bose-Einstein condensate (BEC) and crossover regimes where the electron -hole pairs are well localized. In this case, Hartree-Fock is an excellent approximation for the intralayer correlations. We find in the BEC regime that the effect of the intralayer correlations on superfluid properties is negligible but in the BCS-BEC crossover regime the superfluid gap is significantly weakened by the intralayer correlations. This is caused by the intralayer correlations boosting the number of low -energy particle -hole excitations that drive the screening. We further find that the intralayer correlations suppress the predicted phenomenon in which the average pair size passes through a minimum as the crossover regime is traversed.
Keywords: A1 Journal article; Theory of quantum systems and complex systems; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.109.094512
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“Reduction-enhanced water flux through layered graphene oxide (GO) membranes stabilized with H3O+ and OH- ions”. Gogoi A, Neyts EC, Peeters FM, Physical chemistry, chemical physics 26, 10265 (2024). http://doi.org/10.1039/D3CP04097F
Abstract: Graphene oxide (GO) is one of the most promising candidates for next generation of atomically thin membranes. Nevertheless, one of the major issues for real world application of GO membranes is their undesirable swelling in an aqueous environment. Recently, we demonstrated that generation of H3O+ and OH- ions (e.g., with an external electric field) in the interlayer gallery could impart aqueous stability to the layered GO membranes (A. Gogoi, ACS Appl. Mater. Interfaces, 2022, 14, 34946). This, however, compromises the water flux through the membrane. In this study, we report on reducing the GO nanosheets as a solution to this issue. With the reduction of the GO nanosheets, the water flux through the layered GO membrane initially increases and then decreases again beyond a certain degree of reduction. Here, two key factors are at play. Firstly, the instability of the H-bond network between water molecules and the GO nanosheets, which increases the water flux. Secondly, the pore size reduction in the interlayer gallery of the membranes, which decreases the water flux. We also observe a significant improvement in the salt rejection of the membranes, due to the dissociation of water molecules in the interlayer gallery. In particular, for the case of 10% water dissociation, the water flux through the membranes can be enhanced without altering its selectivity. This is an encouraging observation as it breaks the traditional tradeoff between water flux and salt rejection of a membrane.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Modelling and Simulation in Chemistry (MOSAIC)
Impact Factor: 3.3
DOI: 10.1039/D3CP04097F
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“McMillan-Ginzburg-Landau theory of singularities and discommensurations in charge density wave states of transition metal dichalcogenides”. Moura VN, Chaves A, Peeters FM, Milošević, MV, Physical review B 109, 094507 (2024). http://doi.org/10.1103/PHYSREVB.109.094507
Abstract: The McMillan-Ginzburg-Landau (MGL) model for charge density waves (CDW) is employed in a systematic phenomenological study of the different phases that have been probed in recent experiments involving transition metal dichalcogenides. We implemented an efficient imaginary time evolution method to solve the MGL equations, which enabled us to investigate the role of different coupling parameters on the CDW patterns and to perform calculations with different energy functionals that lead to several experimentally observed singularities in the CDW phase profiles. In particular, by choosing the appropriate energy functionals, we were able to obtain phases that go beyond the well-known periodic phase slips (discommensurations), exhibiting also topological defects (i.e., vortex-antivortex pairs), domain walls where the CDW order parameter is suppressed, and even CDW with broken rotational symmetry. Finally, we briefly discuss the effect of these different CDW phases on the profile and critical temperature of the competing superconducting state.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.109.094507
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“Exploring the adsorption mechanisms of neurotransmitter and amino acid on Ti3C2-MXene monolayer : insights from DFT calculations”. Ozdemir I, Arkin H, Milošević, MV, V Barth J, Aktuerk E, Surfaces and interfaces 46, 104169 (2024). http://doi.org/10.1016/J.SURFIN.2024.104169
Abstract: In this study, we conducted a systematic density functional theory (DFT) investigation of the interaction between Ti3C2-MXene monolayer and biological molecules dopamine (DA) and serine (Ser) as neurotransmitter and amino acid, respectively. Our calculations show good agreement with previous literature findings for the optimized Ti3C2 monolayer. We found that DA and Ser molecules bind to the Ti3C2 surface with adsorption energies of -2.244 eV and -3.960 eV, respectively. The adsorption of Ser resulted in the dissociation of one H atom. Electronic density of states analyses revealed little changes in the electronic properties of the Ti3C2-MXene monolayer upon adsorption of the biomolecules. We further investigated the interaction of DA and Ser with Ti3C2 monolayers featuring surface -termination with OH functional group, and Ti -vacancy. Our calculations indicate that the adsorption energies significantly decrease in the presence of surface termination, with adsorption energies of -0.097 eV and -0.330 eV for DA and Ser, respectively. Adsorption energies on the Ti -vacancy surface, on the other hand, are calculated to be -3.584 eV and -3.856 eV for DA and Ser, respectively. Our results provide insights into the adsorption behavior of biological molecules on Ti3C2-MXene, demonstrating the potential of this material for biosensing and other biomedical applications. These findings highlight the importance of surface modifications in the development of functional materials and devices based on Ti3C2-MXene, and pave the way for future investigations into the use of 2D materials for biomedical applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.2
DOI: 10.1016/J.SURFIN.2024.104169
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“Charged vacancy in graphene : interplay between Landau levels and atomic collapse resonances”. Wang J, Zhao W-S, Hu Y, Filho RNC, Peeters FM, Physical review B 109, 104103 (2024). http://doi.org/10.1103/PHYSREVB.109.104103
Abstract: The interplay between a magnetic field and the Coulomb potential from a charged vacancy on the electron states in graphene is investigated within the tight-binding model. The Coulomb potential removes locally Landau level degeneracy, while the vacancy introduces a satellite level next to the normal Landau level. These satellite levels are found throughout the positive-energy region, but in the negative-energy region, they turn into atomic collapse resonances. Crossings between Landau levels with different angular quantum number m are found. Unlike the point impurity system in which an anticrossing occurs between Landau levels of the same m, in this work anticrossing is found between the normal Landau level and the vacancy-induced level. The atomic collapse resonance hybridizes with the Landau levels. The charge at which the lowest Landau level m = -1, N = 1 crosses E = 0 increases with enhancing magnetic field. A Landau level scaling anomaly occurs when the charge is larger than the critical charge beta 0.6 and this critical charge is independent of the magnetic field.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.109.104103
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“Magnetization-switching dynamics driven by chiral coupling”. Vermeulen BB, Monteiro MG, Giuliano D, Sorée B, Couet S, Temst K, Nguyen VD, Physical review applied 21, 024050 (2024). http://doi.org/10.1103/PHYSREVAPPLIED.21.024050
Abstract: The Dzyaloshinskii-Moriya interaction (DMI) is known to play a central role in stabilizing chiral spin textures such as skyrmions and domain walls (DWs). Electrical manipulation of DW and skyrmion motion offers possibilities for next-generation, scalable and energy-efficient spintronic devices. However, achieving the full potential of these nanoscale devices requires overcoming several challenges, including reliable electrical write and read techniques for these magnetic objects, and addressing pinning and Joule-heating concerns. Here, through micromagnetic simulations and analytical modeling, we show that DMI can directly induce magnetization switching of a nanomagnet with perpendicular magnetic anisotropy (PMA). We find that the switching is driven by the interplay between the DMI-induced magnetic frustration and the PMA. By introducing magnetic tunnel junctions to electrically access and control the magnetization direction of the PMA nanomagnet, we first show the potential of this concept to enable high-density fieldfree spin-orbit torque magnetic random-access memory. Ultimately, we demonstrate that it offers a way of transferring and processing spin information for logic operation without relying on current-driven DW or skyrmion motion.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4.6
DOI: 10.1103/PHYSREVAPPLIED.21.024050
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“Competition of disorder and electron-phonon coupling in 2H-TaSe2-xSx (0≤x≤2) as evidenced by Raman spectroscopy”. Blagojević, J, Mijin SD, Bekaert J, Opačić, M, Liu Y, Milošević, MV, Petrović, C, Popović, ZV, Lazarević, N, Physical review materials 8, 024004 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.024004
Abstract: The vibrational properties of 2H-TaSe<sub>2-x</sub>S<sub>x</sub> (0≤x≤2) single crystals were probed using Raman spectroscopy and density functional theory calculations. The end members revealed two out of four symmetry-predicted Raman active modes, together with the pronounced two-phonon structure, attributable to the enhanced electron-phonon coupling. Additional peaks become observable due to crystallographic disorder for the doped samples. The evolution of the E<sub>2</sub>g<sup>2</sup> mode Fano parameter reveals that the disorder has a weak impact on electron-phonon coupling, which is also supported by the persistence of two-phonon structure in doped samples. As such, this research provides thorough insights into the lattice properties, the effects of crystallographic disorder on Raman spectra, and the interplay of this disorder with the electron-phonon coupling in 2H-TaSe<sub>2-x</sub>S<sub>x</sub> compounds.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.024004
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“Towards fully electrically controlled domain-wall logic”. Vermeulen BB, Raymenants E, Pham VT, Pizzini S, Sorée B, Wostyn K, Couet S, Nguyen VD, Temst K, AIP advances 14, 025030 (2024). http://doi.org/10.1063/9.0000811
Abstract: Utilizing magnetic tunnel junctions (MTJs) for write/read and fast spin-orbit-torque (SOT)-driven domain-wall (DW) motion for propagation, enables non-volatile logic and majority operations, representing a breakthrough in the implementation of nanoscale DW logic devices. Recently, current-driven DW logic gates have been demonstrated via magnetic imaging, where the Dzyaloshinskii-Moriya interaction (DMI) induces chiral coupling between perpendicular magnetic anisotropy (PMA) regions via an in-plane (IP) oriented region. However, full electrical operation of nanoscale DW logic requires electrical write/read operations and a method to pattern PMA and IP regions compatible with the fabrication of PMA MTJs. Here, we study the use of a Hybrid Free Layer (HFL) concept to combine an MTJ stack with DW motion materials, and He+ ion irradiation to convert the stack from PMA to IP. First, we investigate the free layer thickness dependence of 100-nm diameter HFL-MTJ devices and find an optimal CoFeB thickness, from 7 to 10 angstrom, providing high tunneling magnetoresistance (TMR) readout and efficient spin-transfer torque (STT) writing. We then show that high DMI materials, like Pt/Co, can be integrated into an MTJ stack via interlayer exchange coupling with the CoFeB free layer. In this design, DMI values suitable for SOT-driven DW motion are measured by asymmetric bubble expansion. Finally, we demonstrate that He+ irradiation reliably converts the coupled free layers from PMA to IP. These findings offer a path toward the integration of fully electrically controlled DW logic circuits.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
DOI: 10.1063/9.0000811
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“Terahertz magneto-optical properties of Nitrogen-doped diamond”. Xiao H, Wen H, Xu W, Cheng Y, Zhang J, Cheng X, Xiao Y, Ding L, Li H, He B, Peeters FM, Infrared physics and technology 138, 105237 (2024). http://doi.org/10.1016/J.INFRARED.2024.105237
Abstract: Nitrogen-doped diamond (N-D) is one of the most important carbon-based electronic and optical materials. Here we study the terahertz (THz) magneto-optical (MO) properties of N-D grown by microwave plasma-enhanced chemical vapor deposition. The optical microscope, SEM, XRD, Raman spectrum, FTIR spectroscopy and XPS are used for the characterization of N-D samples. Applying THz time-domain spectroscopy (TDS), in combination with the polarization test and the presence of magnetic field in Faraday geometry, THz MO transmissions through N-D are measured from 0 to 8 T at 80 K. The complex right- and left-handed circular transmission coefficients and MO conductivities for N-D are obtained accordingly. Through fitting the experimental results with theoretical formulas of the dielectric constant and MO conductivities for an electron gas, we are able to determine magneto-optically the key electronic parameters of N-D, such as the static dielectric constant epsilon b, the electron density ne, the electronic relaxation time tau, the electronic localization factor alpha and, particularly, the effective electron mass m* obtained under non-resonant condition. The dependence of these parameters upon magnetic field is examined and analyzed. We find that the MO conductivities of N-D can be described rightly by the MO Drude-Smith formulas developed by us previously. It is shown that N-doping and the presence of the magnetic field can lead towards the larger epsilon b and heavier m* in diamond, while ne/tau/alpha in N-D decreases/increases/decreases with increasing magnetic field. The results obtained from this work are benefit to us in gaining an in-depth understanding of the electronic and optoelectronic properties of N-D.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.3
DOI: 10.1016/J.INFRARED.2024.105237
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“Comparative analysis of tight-binding models for transition metal dichalcogenides”. Jorissen B, Covaci L, Partoens B, SciPost physics core 7, 004 (2024). http://doi.org/10.21468/SCIPOSTPHYSCORE.7.1.004
Abstract: We provide a comprehensive analysis of the prominent tight-binding (TB) models for transition metal dichalcogenides (TMDs) available in the literature. We inspect the construction of these TB models, discuss their parameterization used and conduct a thorough comparison of their effectiveness in capturing important electronic properties. Based on these insights, we propose a novel TB model for TMDs designed for enhanced computational efficiency. Utilizing MoS2 as a representative case, we explain why specific models offer a more accurate description. Our primary aim is to assist researchers in choosing the most appropriate TB model for their calculations on TMDs.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
DOI: 10.21468/SCIPOSTPHYSCORE.7.1.004
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“Observation of temperature induced phase transitions in TiO superconducting thin film via infrared measurement”. Zhou S, Zhang C, Xu W, Zhang J, Xiao Y, Ding L, Wen H, Cheng X, Hu C, Li H, Li X, Peeters FM, Infrared physics and technology 137, 105160 (2024). http://doi.org/10.1016/J.INFRARED.2024.105160
Abstract: In contrast to conventional polycrystalline titanium oxide (TiO), it was found recently that the superconducting transition temperature Tc can be significantly enhanced from about 2 K to 7.4 K in cubic TiO thin films grown epitaxially on alpha-Al2O3 substrates. This kind of TiO film is also expected to have distinctive optoelectronic properties, which are still not very clear up to now. Herein, by using infrared (IR) reflection measurement we investigate the temperature-dependent optoelectronic response of a cubic TiO thin film, in which temperature induced phase transitions are observed. The semiconductor-, metallic- and semiconductor-like electronic phases of this superconducting film are found in the temperature regimes from 10 to 110 K, 110 to 220 K and above 220 K, respectively. The results obtained optically are consistent with those measured by transport experiment. Furthermore, based on an improved reflection model developed here, we extract the complex optical conductivity of the cubic TiO thin film. We are able to approximately determine the characteristic parameters (e.g., effective electron mass, carrier density, scattering time, etc.) for different electronic phases by fitting the optical conductivity with the modified Lorentz formula. These results not only deepen our understanding of the fundamental physics for cubic TiO thin films but also may find applications in optoelectronic devices based on superconductors.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.3
DOI: 10.1016/J.INFRARED.2024.105160
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“Reduction of magnetic interaction due to clustering in doped transition-metal dichalcogenides : a case study of Mn-, V-, and Fe-doped WSe₂”. Tiwari S, Van de Put M, Sorée B, Hinkle C, Vandenberghe WG, ACS applied materials and interfaces 16, 4991 (2024). http://doi.org/10.1021/ACSAMI.3C14114
Abstract: Using Hubbard-U-corrected density functional theory calculations, lattice Monte Carlo simulations, and spin Monte Carlo simulations, we investigate the impact of dopant clustering on the magnetic properties of WSe2 doped with period four transition metals. We use manganese (Mn) and iron (Fe) as candidate n-type dopants and vanadium (V) as the candidate p-type dopant, substituting the tungsten (W) atom in WSe2. Specifically, we determine the strength of the exchange interaction in Fe-, Mn-, and V-doped WSe2 in the presence of clustering. We show that the clusters of dopants are energetically more stable than discretely doped systems. Further, we show that in the presence of dopant clustering, the magnetic exchange interaction significantly reduces because the magnetic order in clustered WSe2 becomes more itinerant. Finally, we show that the clustering of the dopant atoms has a detrimental effect on the magnetic interaction, and to obtain an optimal Curie temperature, it is important to control the distribution of the dopant atoms.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 9.5
DOI: 10.1021/ACSAMI.3C14114
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“Tailoring weak and metallic phases in a strong topological insulator by strain and disorder : conductance fluctuations signatures”. Shafiei M, Fazileh F, Peeters FM, Milošević, MV, Physical review B 109, 045129 (2024). http://doi.org/10.1103/PHYSREVB.109.045129
Abstract: Transport measurements are readily used to probe different phases in disordered topological insulators (TIs), where determining topological invariants explicitly is challenging. On that note, universal conductance fluctuations (UCF) theory asserts the conductance G for an ensemble has a Gaussian distribution, and that standard deviation 8G depends solely on the symmetries and dimensions of the system. Using a real-space tight -binding Hamiltonian on a system with Anderson disorder, we explore conductance fluctuations in a thin Bi2Se3 film and demonstrate the agreement of their behavior with UCF hypotheses. We further show that magnetic field applied out-of-plane breaks the time -reversal symmetry and transforms the system's Wigner-Dyson class from root symplectic to unitary, increasing 8G by 2. Finally, we reveal that while Bi2Se3 is a strong TI, weak TI and metallic phases can be stabilized in presence of strain and disorder, and detected by monitoring the conductance fluctuations.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 1
DOI: 10.1103/PHYSREVB.109.045129
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“Interface thermal conductivities induced by van der Waals interactions”. Dong HM, Liang HP, Tao ZH, Duan YF, Milošević, MV, Chang K, Physical chemistry, chemical physics 26, 4047 (2024). http://doi.org/10.1039/D3CP05377F
Abstract: The interface heat transfer of two layers induced by van der Waals (vdW) contacts is theoretically investigated, based on first-principles calculations at low temperatures. The results suggest that out-of-plane acoustic phonons with low frequencies dominate the interface thermal transport due to the vdW interaction. The interface thermal conductivity is proportional to the cubic of temperature at very low temperatures, but becomes linearly proportional to temperature as temperature increases. We show that manipulating the strain alters vdW coupling, leading to increased interfacial thermal conductivity at the interface. Our findings provide valuable insights into the interface heat transport in vdW heterostructures and support further design and optimization of electronic and optoelectronic nanodevices based on vdW contacts. The heat transfer induced by van der Waals contacts is dominated by ZA phonons. The interface thermal conductivity is proportional to the cubic of temperature, but becomes linearly proportional to temperature as temperature increases.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.3
DOI: 10.1039/D3CP05377F
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“On the coupling of magnetic moments to superconducting quantum interference devices”. Linek J, Wyszynski M, Müller B, Korinski D, Milošević, MV, Kleiner R, Koelle D, Superconductor science and technology 37, 025010 (2024). http://doi.org/10.1088/1361-6668/AD1AE9
Abstract: We investigate the coupling factor phi( mu) that quantifies the magnetic flux phi per magnetic moment mu of a point-like magnetic dipole that couples to a superconducting quantum interference device (SQUID). Representing the dipole by a tiny current-carrying (Amperian) loop, the reciprocity of mutual inductances of SQUID and Amperian loop provides an elegant way of calculating phi(mu)(r,e(mu)) vs. position r and orientation e(mu) of the dipole anywhere in space from the magnetic field B-J(r) produced by a supercurrent circulating in the SQUID loop. We use numerical simulations based on London and Ginzburg-Landau theory to calculate phi (mu) from the supercurrent density distributions in various superconducting loop geometries. We treat the far-field regime ( r greater than or similar to a= inner size of the SQUID loop) with the dipole placed on (oriented along) the symmetry axis of circular or square shaped loops. We compare expressions for phi (mu) from simple filamentary loop models with simulation results for loops with finite width w (outer size A > alpha), thickness d and London penetration depth lambda(L )and show that for thin ( d << alpha ) and narrow (w < alpha) loops the introduction of an effective loop size a(eff) in the filamentary loop-model expressions results in good agreement with simulations. For a dipole placed right in the center of the loop, simulations provide an expression phi(mu)(a,A,d,lambda(L)) that covers a wide parameter range. In the near-field regime (dipole centered at small distance z above one SQUID arm) only coupling to a single strip representing the SQUID arm has to be considered. For this case, we compare simulations with an analytical expression derived for a homogeneous current density distribution, which yields excellent agreement for lambda(L)>w,d . Moreover, we analyze the improvement of phi(mu) provided by the introduction of a narrow constriction in the SQUID arm below the magnetic dipole.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.6
DOI: 10.1088/1361-6668/AD1AE9
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“Chlorinated phosphorene for energy application”. Hassani N, Yagmurcukardes M, Peeters FM, Neek-Amal M, Computational materials science 231, 112625 (2024). http://doi.org/10.1016/J.COMMATSCI.2023.112625
Abstract: The influence of decoration with impurities and the composition dependent band gap in 2D materials has been the subject of debate for a long time. Here, by using Density Functional Theory (DFT) calculations, we systematically disclose physical properties of chlorinated phosphorene having the stoichiometry of PmCln. By analyzing the adsorption energy, charge density, migration energy barrier, structural, vibrational, and electronic properties of chlorinated phosphorene, we found that (I) the Cl-P bonds are strong with binding energy Eb =-1.61 eV, decreases with increasing n. (II) Cl atoms on phosphorene have anionic feature, (III) the migration path of Cl on phosphorene is anisotropic with an energy barrier of 0.38 eV, (IV) the phonon band dispersion reveal that chlorinated phosphorenes are stable when r <= 0.25 where r = m/n, (V) chlorinated phosphorenes is found to be a photonic crystal in the frequency range of 280 cm-1 to 325 cm-1, (VI) electronic band structure of chlorinated phosphorenes exhibits quasi-flat bands emerging around the Fermi level with widths in the range of 22 meV to 580 meV, and (VII) Cl adsorption causes a semiconducting to metallic/semi-metallic transition which makes it suitable for application as an electroactive material. To elucidate this application, we investigated the change in binding energy (Eb), specific capacity, and open-circuit voltage as a function of the density of adsorbed Cl. The theoretical storage capacity of the chlorinated phosphorene is found to be 168.19 mA h g-1with a large average voltage (similar to 2.08 V) which is ideal number as a cathode in chloride-ion batteries.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.3
Times cited: 2
DOI: 10.1016/J.COMMATSCI.2023.112625
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“Superconductor-semiconductor hybrid capacitance with a nonlinear charge-voltage profile”. Lauwens J, Kerkhofs L, Sala A, Sorée B, Journal of physics: D: applied physics 57, 025301 (2024). http://doi.org/10.1088/1361-6463/ACFE87
Abstract: Electronic devices that work in the quantum regime often employ hybrid nanostructures to bring about a nonlinear behaviour. The nonlinearity that these can provide has proven to be useful, in particular, for applications in quantum computation. Here we present a hybrid device that acts as a capacitor with a nonlinear charge-voltage relation. The device consists of a nanowire placed between the plates of a coplanar capacitor, with a co-parallel alignment. At low temperatures, due to the finite density of states on the nanowire, the charge distribution in the capacitor is uneven and energy-dependent, resulting in a charge-dependent effective capacitance. We study this system analytically and numerically, and show that the nonlinearity of the capacitance is significant enough to be utilized in circuit quantum electrodynamics. The resulting nonlinearity can be switched on, modulated, and switched off by an external potential, thus making this capacitive device highly versatile for uses in quantum computation.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1088/1361-6463/ACFE87
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“Defective biphenylene as high-efficiency hydrogen evolution catalysts”. Luo Y, He Y, Ding Y, Zuo L, Zhong C, Ma Y, Sun M, Inorganic chemistry 63, 1136 (2023). http://doi.org/10.1021/ACS.INORGCHEM.3C03503
Abstract: Electrocatalysts play a pivotal role in advancing the application of water splitting for hydrogen production. This research unveils the potential of defective biphenylenes as high-efficiency catalysts for the hydrogen evolution reaction. Using first-principles simulations, we systematically investigated the structure, stability, and catalytic performance of defective biphenylenes. Our findings unveil that defect engineering significantly enhances the electrocatalytic activity for hydrogen evolution. Specifically, biphenylene with a double-vacancy defect exhibits an outstanding Gibbs free energy of -0.08 eV, surpassing that of Pt, accompanied by a remarkable exchange current density of -3.08 A cm(-2), also surpassing that of Pt. Furthermore, we find the preference for the Volmer-Heyrovsky mechanism in the hydrogen evolution reaction, with a low energy barrier of 0.80 eV. This research provides a promising avenue for developing novel metal-free electrocatalysts for water splitting with earth-abundant carbon elements, making a significant step toward sustainable hydrogen production.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4.6
DOI: 10.1021/ACS.INORGCHEM.3C03503
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“Synergetic enhancement of quantum yield and exciton lifetime of monolayer WS₂, by proximal metal plate and negative electric bias”. Tran TT, Lee Y, Roy S, Tran TU, Kim Y, Taniguchi T, Watanabe K, Milošević, MV, Lim SC, Chaves A, Jang JI, Kim J, ACS nano 18, 220 (2023). http://doi.org/10.1021/ACSNANO.3C05667
Abstract: The efficiency of light emission is a critical performance factor for monolayer transition metal dichalcogenides (1L-TMDs) for photonic applications. While various methods have been studied to compensate for lattice defects to improve the quantum yield (QY) of 1L-TMDs, exciton-exciton annihilation (EEA) is still a major nonradiative decay channel for excitons at high exciton densities. Here, we demonstrate that the combined use of a proximal Au plate and a negative electric gate bias (NEGB) for 1L-WS2 provides a dramatic enhancement of the exciton lifetime at high exciton densities with the corresponding QY enhanced by 30 times and the EEA rate constant decreased by 80 times. The suppression of EEA by NEGB is attributed to the reduction of the defect-assisted EEA process, which we also explain with our theoretical model. Our results provide a synergetic solution to cope with EEA to realize high-intensity 2D light emitters using TMDs.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 17.1
DOI: 10.1021/ACSNANO.3C05667
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“Optical spectrum of n-type and p-type monolayer MoS₂, in the presence of proximity-induced interactions”. Liu J, Xu W, Xiao YM, Ding L, Li HW, Peeters FM, Journal of applied physics 134, 224301 (2023). http://doi.org/10.1063/5.0181003
Abstract: In this paper, we examined the effects of proximity-induced interactions such as Rashba spin-orbit coupling and effective Zeeman fields (EZFs) on the optical spectrum of n-type and p-type monolayer (ML)-MoS2. The optical conductivity is evaluated using the standard Kubo formula under random-phase approximation by including the effective electron-electron interaction. It has been found that there exist two absorption peaks in n-type ML-MoS2 and two knife shaped absorptions in p-type ML-MoS2, which are contributed by the inter-subband spin-flip electronic transitions within conduction and valence bands at valleys K and K ' with a lifted valley degeneracy. The optical absorptions in n-type and p-type ML-MoS 2 occur in THz and infrared radiation regimes and the position, height, and shape of them can be effectively tuned by Rashba parameter, EZF parameters, and carrier density. The interesting theoretical predictions in this study would be helpful for the experimental observation of the optical absorption in infrared to THz bandwidths contributed by inter-subband spin-flip electronic transitions in a lifted valley degeneracy monolayer transition metal dichalcogenides system. The obtained results indicate that ML-MoS2 with the platform of proximity interactions make it a promising infrared and THz material for optics and optoelectronics.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.2
DOI: 10.1063/5.0181003
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“A combined experimental and computational approach to understanding CdS pigment oxidation in a renowned early 20th century painting”. Mayda S, Monico L, Krishnan D, De Meyer S, Cotte M, Garrevoet J, Falkenberg G, Sandu ICA, Partoens B, Lamoen D, Romani A, Miliani C, Verbeeck J, Janssens K, Chemistry of materials 35, 10403 (2023). http://doi.org/10.1021/ACS.CHEMMATER.3C01470
Abstract: Cadmium sulfide (CdS)-based yellow pigments have been used in a number of early 20th century artworks, including The Scream series painted by Edvard Munch. Some of these unique paintings are threatened by the discoloration of these CdS-based yellow oil paints because of the oxidation of the original sulfides to sulfates. The experimental data obtained here prove that moisture and cadmium chloride compounds play a key role in promoting such oxidation. To clarify how these two factors effectively prompt the process, we studied the band alignment between CdS, CdCl2, and Cd-(OH)Cl as well as the radicals center dot OH and H3O center dot by density functional theory (DFT) methods. Our results show that a stack of several layers of Cd-(OH)Cl creates a pocket of positive holes at the Cl-terminated surface and a pocket of electrons at the OH-terminated surface by leading in a difference in ionization energy at both surfaces. The resulting band alignment indicates that Cd-(OH)Cl can indeed play the role of an oxidative catalyst for CdS in a moist environment, thus providing an explanation for the experimental evidence.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT); Antwerp X-ray Imaging and Spectroscopy (AXIS)
Impact Factor: 8.6
DOI: 10.1021/ACS.CHEMMATER.3C01470
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