“Silicon and germanium adamantane and diamantane monolayers as two-dimensional anisotropic direct-gap semiconductors”. Santos-Castro G, Pandey T, Bruno CHV, Santos Caetano EW, Milošević, MV, Chaves A, Freire VN, Physical review B 108, 035302 (2023). http://doi.org/10.1103/PHYSREVB.108.035302
Abstract: Structural and electronic properties of silicon and germanium monolayers with two different diamondoid crystal structures are detailed ab initio. Our results show that, despite Si and Ge being well-known indirect gap semiconductors in their bulk form, their adamantane and diamantane monolayers can exhibit optically active direct gap in the visible frequency range, with highly anisotropic effective masses, depending on the monolayer crystal structure. Moreover, we reveal that gaps in these materials are highly tunable with applied strain. These stable monolayer forms of Si and Ge are therefore expected to help bridging the gap between the fast growing area of opto-electronics in two-dimensional materials and the established silicon-based technologies.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.108.035302
|
“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
|
“Collective excitations in three-dimensional Dirac systems”. Li QN, Vasilopoulos P, Peeters FM, Xu W, Xiao YM, Milošević, MV, Physical review B 109, 115123 (2024). http://doi.org/10.1103/PHYSREVB.109.115123
Abstract: We provide the plasmon spectrum and related properties of the three-dimensional (3D) Dirac semimetals Na 3 Bi and Cd 3 As 2 based on the random -phase approximation. The necessary one -electron eigenvalues and eigenfunctions are obtained from an effective k <middle dot> p Hamiltonian. Below the energy at which the velocity v z along the k z axis vanishes, the density of states differs drastically from that of a 3D electron gas (3DEG) or graphene. The dispersion relation is anisotropic for wave vectors parallel ( q ) and perpendicular ( q z ) to the ( x , y ) plane and is markedly different than that of graphene or a 3DEG. The same holds for the energy -loss function. Both depend sensitively on the position of the Fermi energy E F relative to the region of the Berry curvature of the bands. For E F below the energy at which v z vanishes, the range of the relevant wave vectors q and q z shrinks, for q z by about one order of magnitude.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.109.115123
|
“High-Tc Berezinskii-Kosterlitz-Thouless transition in two-dimensional superconducting systems with coupled deep and quasiflat electronic bands with Van Hove singularities”. Paramasivam SK, Gangadharan SP, Milošević, MV, Perali A, Physical review B 110, 024507 (2024). http://doi.org/10.1103/PHYSREVB.110.024507
Abstract: In the pursuit of higher critical temperature of superconductivity, quasiflat electronic bands and Van Hove singularities in two dimensions (2D) have emerged as a potential approach to enhance Cooper pairing on the basis of mean-field expectations. However, these special electronic features suppress the superfluid stiffness and, hence, the Berezinskii-Kosterlitz-Thouless (BKT) transition in 2D superconducting systems, leading to the emergence of a significant pseudogap regime due to superconducting fluctuations. In the strong-coupling regime, one finds that superfluid stiffness is inversely proportional to the superconducting gap, which is the predominant factor contributing to the strong suppression of superfluid stiffness. Here we reveal that the aforementioned limitation is avoided in a 2D superconducting electronic system with a quasiflat electronic band with a strong pairing strength coupled to a deep band with weak electronic pairing strength. Owing to the multiband effects, we demonstrate a screening-like mechanism that circumvents the suppression of the superfluid stiffness. We report the optimal conditions for achieving a large enhancement of the BKT transition temperature and a substantial shrinking of the pseudogap regime by tuning the intraband couplings and the pair-exchange coupling between the two band-condensates.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.110.024507
|
“Longitudinal and transverse mobilities of n-type monolayer transition metal dichalcogenides in the presence of proximity-induced interactions at low temperature”. Liu J, Xu W, Xiao YM, Ding L, Li HW, Van Duppen B, Milošević, MV, Peeters FM, Physical review B 109, 195418 (2024). http://doi.org/10.1103/PHYSREVB.109.195418
Abstract: We present a detailed theoretical investigation on the electronic transport properties of n-type monolayer (ML) transition metal dichalcogenides (TMDs) at low temperature in the presence of proximity-induced interactions such as Rashba spin-orbit coupling (RSOC) and the exchange interaction. The electronic band structure is calculated by solving the Schr & ouml;dinger equation with a k <middle dot> p Hamiltonian, and the electric screening induced by electron-electron interaction is evaluated under a standard random phase approximation approach. In particular, the longitudinal and transverse or Hall mobilities are calculated by using a momentum-balance equation derived from a semiclassical Boltzmann equation, where the electron-impurity interaction is considered as the principal scattering center at low temperature. The obtained results show that the RSOC can induce the in-plane spin components for spin-split subbands in different valleys, while the exchange interaction can lift the energy degeneracy for electrons in different valleys. The opposite signs of Berry curvatures in the two valleys would introduce opposite directions of Lorentz force on valley electrons. As a result, the transverse currents from nondegenerate valleys can no longer be canceled out so that the transverse current or Hall mobility can be observed. Interestingly, we find that at a fixed effective Zeeman field, the lowest spin-split conduction subband in ML-TMDs can be tuned from one in the K'-valley to one in the K-valley by varying the Rashba parameter. The occupation of electrons in different valleys also varies with changing carrier density. Therefore, we can change the magnitude and direction of the Hall current by varying the Rashba parameter, effective Zeeman field, and carrier density by, e.g., the presence of a ferromagnetic substrate and/or applying a gate voltage. By taking the ML-MoS2 as an example, these effects are demonstrated and examined. The important and interesting theoretical findings can be beneficial to experimental observation of the valleytronic effect and to gaining an in-depth understanding of the ML-TMD systems in the presence of proximity-induced interactions.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.109.195418
|
“Magneto-optical conductivity of monolayer transition metal dichalcogenides in the presence of proximity-induced exchange interaction and external electrical field”. Li Y, Xiao YM, Xu W, Ding L, Milošević, MV, Peeters FM, Physical review B 109, 165441 (2024). http://doi.org/10.1103/PHYSREVB.109.165441
Abstract: We theoretically investigate the magneto-optical (MO) properties of monolayer (ML) transition metal dichalcogenides (TMDs) in the presence of external electrical and quantizing magnetic fields and of the proximity-induced exchange interaction. The corresponding Landau Level (LL) structure is studied by solving the Schr & ouml;dinger equation and the spin polarization in ML-TMDs under the action of the magnetic field is evaluated. The impact of trigonal warping on LLs and MO absorption is examined. Furthermore, the longitudinal MO conductivity is calculated through the dynamical dielectric function under the standard random-phase approximation (RPA) with the Kubo formula. We take ML-MoS 2 as an example to examine the effects of proximity-induced exchange interaction, external electrical and magnetic fields on the MO conductivity induced via intra- and interband electronic transitions among the LLs. For intraband electronic transitions within the conduction or valence bands, we can observe two absorption peaks in terahertz (THz) frequency range. While the interband electronic transitions between conduction and valence LLs show a series of absorption peaks in the visible range. We find that the proximity-induced exchange interaction, the carrier density, the strengths of the external electrical and magnetic fields can effectively modulate the positions of the absorption peaks and the shapes of the MO absorption spectra. The results obtained from this study can benefit to an in-depth understanding of the MO properties of ML-TMDs which can be potentially applied for magneto-optic, spintronic, and valleytronic devices working in visible to THz frequency bandwidths.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.109.165441
|
“Strain and stacking registry effects on the hyperbolicity of exciton polaritons in few-layer black phosphorus”. Thomen DMN, Sevik C, Milošević, MV, Teles LK, Chaves A, Physical review B 109, 245413 (2024). http://doi.org/10.1103/PHYSREVB.109.245413
Abstract: We analyze, from first -principles calculations, the excitonic properties of monolayer black phosphorus (BP) under strain, as well as of bilayer BP with different stacking registries, as a base platform for the observation and use of hyperbolic polaritons. In the unstrained case, our results confirm the in -plane hyperbolic behavior of polaritons coupled to the ground -state excitons in both mono- and bilayer systems, as observed in recent experiments. With strain, we reveal that the exciton-polariton hyperbolicity in monolayer BP is enhanced (reduced) by compressive (tensile) strain in the zig-zag direction of the crystal. In the bilayer case, different stacking registries are shown to exhibit hyperbolic exciton polaritons with different dispersion, while also peaking at different frequencies. This renders both mechanical stress and stacking registry control as practical tools for tuning physical properties of hyperbolic exciton polaritons in black phosphorus, which facilitates detection and further optoelectronic use of these quasiparticles.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.109.245413
|
“Vortical versus skyrmionic states in the topological phase of a twisted bilayer with d-wave superconducting pairing”. Cadorim LR, Sardella E, Milošević, MV, Physical review B 110, 064508 (2024). http://doi.org/10.1103/PHYSREVB.110.064508
Abstract: It was recently shown that a chiral topological phase emerges from the coupling of two twisted monolayers of superconducting Bi2Sr2CaCu2O8+delta for 2 Sr 2 CaCu 2 O 8 +delta for certain twist angles. In this work, we reveal the behavior of such twisted superconducting bilayers with d x 2 – y 2 pairing symmetry in the presence of an applied magnetic field. Specifically, we show that the emergent vortex matter can serve as a smoking gun for the detection of topological superconductivity in such bilayers. Moreover, we report two distinct skyrmionic states that characterize the chiral topological phase and provide a full account of their experimental signatures and their evolution with the twist angle.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
DOI: 10.1103/PHYSREVB.110.064508
|
“Strain-Induced Exciton Hybridization in WS2 Monolayers Unveiled by Zeeman-Splitting Measurements”. Blundo E, Faria PE Jr, Surrente A, Pettinari G, Prosnikov MA, Olkowska-Pucko K, Zollner K, Wozniak T, Chaves A, Kazimierczuk T, Felici M, Babinski A, Molas MR, Christianen PCM, Fabian J, Polimeni A, Physical review letters 129, 067402 (2022). http://doi.org/10.1103/PHYSREVLETT.129.067402
Abstract: Mechanical deformations and ensuing strain are routinely exploited to tune the band gap energy and to enhance the functionalities of two-dimensional crystals. In this Letter, we show that strain leads also to a strong modification of the exciton magnetic moment in WS2 monolayers. Zeeman-splitting measurements under magnetic fields up to 28.5 T were performed on single, one-layer-thick WS2 microbubbles. The strain of the bubbles causes a hybridization of k-space direct and indirect excitons resulting in a sizable decrease in the modulus of they factor of the ground-state exciton. These findings indicate that strain may have major effects on the way the valley number of excitons can be used to process binary information in two-dimensional crystals.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1103/PHYSREVLETT.129.067402
|
“Vibrational properties and thermal transport in quaternary chalcogenides : the case of Te-based compositions”. Shi W, Pandey T, Lindsay L, Woods LM, Physical review materials 5, 045401 (2021). http://doi.org/10.1103/PHYSREVMATERIALS.5.045401
Abstract: Vibrational thermal properties of CuZn2InTe4, AgZn2InTe4, and Cu2CdSnTe4, derived from binary II-VI zinc-blendes, are reported based on first-principles calculations. While the chalcogenide atoms in these materials have the same lattice positions, the cation atom arrangements vary, resulting in different crystal symmetries and subsequent properties. The compositional differences have important effects on the vibrational thermal characteristics of the studied materials, which demonstrate that low-frequency optical phonons hybridize with acoustic phonons and lead to enhanced phonon-phonon scattering and low lattice thermal conductivities. The phonon density of states, mode Gruneisen parameters, and phonon scattering rates are also calculated, enabling deeper insight into the microscopic thermal conduction processes in these materials. Compositional variations drive differences among the three materials considered here; nonetheless, their structural similarities and generally low thermal conductivities (0.5-4 W/mK at room temperature) suggest that other similar II-VI zinc-blende derived materials will also exhibit similarly low values, as also corroborated by experimental data. This, combined with the versatility in designing a variety of motifs on the overall structure, makes quaternary chalcogenides interesting for thermal management and energy conversion applications that require low thermal conductivity.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1103/PHYSREVMATERIALS.5.045401
|
“Two-dimensional heterostructures formed by graphenelike ZnO and MgO monolayers for optoelectronic applications”. Seyedmohammadzadeh M, Sevik C, Guelseren O, Physical review materials 6, 104004 (2022). http://doi.org/10.1103/PHYSREVMATERIALS.6.104004
Abstract: Two-dimensional heterostructures are an emerging class of materials for novel applications because of extensive engineering potential by tailoring intriguing properties of different layers as well as the ones arising from their interface. A systematic investigation of mechanical, electronic, and optical properties of possible heterostructures formed by bilayer structures graphenelike ZnO and MgO monolayers is presented. Different functionality of each layer makes these heterostructures very appealing for device applications. ZnO layer is convenient for electron transport in these structures, while MgO layer improves electron collection. At the outset, all of the four possible stacking configurations across the heterostructure are mechanically stable. In addition, stability analysis using phonon dispersion reveals that the AB stacking formed by placing the Mg atom on top of the O atom of the ZnO layer is also dynamically stable at zero temperature. Henceforth, we have investigated the optical properties of these stable heterostructures by applying many-body perturbation theory within the framework of GW approximation and solving the Bethe-Salpeter equation. It is demonstrated that strong excitonic effects reduce the optical band gap to the visible light spectrum range. These results show that this new two-dimensional form of ZnO/MgO heterostructures open an avenue for novel optoelectronic device applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.6.104004
|
“Defect-limited thermal conductivity in MoS₂”. Polanco CA, Pandey T, Berlijn T, Lindsay L, Physical review materials 4, 014004 (2020). http://doi.org/10.1103/PHYSREVMATERIALS.4.014004
Abstract: The wide measured range of thermal conductivities (k) for monolayer MoS2 and the corresponding incongruent calculated values in the literature all suggest that extrinsic defect thermal resistance is significant and varied in synthesized samples of this material. Here we present defect-mediated thermal transport calculations of MoS2 using interatomic forces derived from density functional theory combined with Green's function methods to describe phonon-point-defect interactions and a Peierls-Boltzmann formalism for transport. Conductivity calculations for bulk and monolayer MoS2 using different density functional formalisms are compared. Nonperturbative first-principles methods are used to describe defect-mediated spectral functions, scattering rates, and phonon k, particularly from sulfur vacancies (VS), and in the context of the plethora of measured and calculated literature values. We find that k of monolayer MoS2 is sensitive to phonon-VS scattering in the range of experimentally observed densities, and that first-principles k calculations using these densities can explain the range of measured values found in the literature. Furthermore, measured k values for bulk MoS2 are more consistent because VS defects are not as prevalent.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.4.014004
|
“Electronic structures of iMAX phases and their two-dimensional derivatives: A family of piezoelectric materials”. Khazaei M, Wang V, Sevik C, Ranjbar A, Arai M, Yunoki S, Physical review materials 2, 074002 (2018). http://doi.org/10.1103/PHYSREVMATERIALS.2.074002
Abstract: Recently, a group of MAX phases, (Mo2/3Y1/3)(2)AlC, (Mo2/3Sc1/3)(2)AlC, (W2/3Sc1/3)(2)AlC,(W2/3Y1/3)(2)AlC, and (V-2/3 Zr-1/3)(2)AlC, with in-plane ordered double transition metals, named iMAX phases, have been synthesized. Experimentally, some of these MAX phases can be chemically exfoliated into two-dimensional (2D) single- or multilayered transition metal carbides, so-called MXenes. Accordingly, the 2D nanostructures derived from iMAX phases are named iMXenes. Here we investigate the structural stabilities and electronic structures of the experimentally discovered iMAX phases and their possible iMXene derivatives. We show that the iMAX phases and their pristine, F, or OH-terminated iMXenes are metallic. However, upon 0 termination, (Mo2/3Y1/3)(2)C, (Mo2/3Sc1/3)(2)C, (W2/3Y1/3)(2)C, and (W2/3Sc1/3)(2)C iMXenes turn into semiconductors. Owing to the absence of centrosymmetry, the semiconducting iMXenes may find applications in piezoelectricity. Our calculations reveal that the semiconducting iMXenes possess giant piezoelectric coefficients as large as 45 x 10(-)(10) C/m.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1103/PHYSREVMATERIALS.2.074002
|
“Tunable magnon topology in monolayer CrI₃, under external stimuli”. Soenen M, Milošević, MV, Physical review materials 7, 084402 (2023). http://doi.org/10.1103/PHYSREVMATERIALS.7.084402
Abstract: Two-dimensional (2D) honeycomb ferromagnets, such as monolayer chromium trihalides, are predicted to behave as topological magnon insulators, characterized by an insulating bulk and topologically protected edge states, giving rise to a thermal magnon Hall effect. Here we report the behavior of the topological magnons in monolayer CrI3 under external stimuli, including biaxial and uniaxial strain, electric gating, as well as in-plane and out-of-plane magnetic field, revealing that one can thereby tailor the magnetic states as well as the size and the topology of the magnonic bandgap. These findings broaden the perspective of using 2D magnetic materials to design topological magnonic devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.7.084402
|
“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
|
“Electron-phonon coupling and thermal conductivity of MAB compounds”. Kocabas T, Samanta B, Barboza E da S, Sevik C, Milošević, MV, Çakir D, Physical review materials 8, 055002 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.055002
Abstract: We investigated the electron-phonon ( e -ph ) coupling and vibrational thermal conductivity in the representative MAB compounds, namely MoAlB, WAlB, Tc 2 AlB 2 , and Cr 2 AlB 2 . The spectral distribution functions of e -ph interaction, obtained through ab initio linear-response calculations, reveal that the electron-phonon coupling values range from low (0.15) to moderate (0.58). With such e -ph coupling, out of the considered compounds, only Tc 2 AlB 2 exhibits a superconducting transition, at 4 K. We further evaluated the thermal conductivity and associated properties like scattering rates, obtained using ab initio and other methodologies. The latter included the iterative solution of the Peierls-Boltzmann transport equation, using HIPHIVE package for advanced optimization and machine learning techniques, and employing maximum likelihood estimation to approximate scattering rates from a limited set of scattering processes. We found that these methods yield nearly identical predictions for thermal conductivity values, with a significant decrease in the computational cost compared to the first-principles methods. We examined interactions arising from both three-phonon (3 ph ) and four -phonon (4 ph ) scattering processes. The 4 ph interactions demonstrated a smaller yet significant impact on the overall vibrational thermal conductivity, most notably in Tc 2 AlB 2 . Our findings indicate that Cr 2 AlB 2 has the highest thermal conductivity across all considered crystal directions, with the thermal conductivity being spatially anisotropic, most pronouncedly in Tc 2 AlB 2 . Finally, we show that empirical expressions based on Slack models are well suited for screening the thermal conductivity properties of MAB phases, and can be employed to establish upper and lower limits of their thermal conductivity.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.055002
|
“First-principles exploration of superconductivity in intercalated bilayer borophene phases”. Šoškić, BN, Bekaert J, Sevik C, Šljivančanin Ž, Milošević, MV, Physical review materials 8, 064803 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.064803
Abstract: We explore the emergence of phonon-mediated superconductivity in bilayer borophenes by controlled intercalation with elements from the groups of alkali, alkaline-earth, and transition metals, using systematic first-principles and Eliashberg calculations. We show that the superconducting properties are primarily governed by the interplay between the out-of-plane (????????) boron states and the partially occupied in-plane (????+????????,????) bonding states at the Fermi level. Our Eliashberg calculations indicate that intercalation with alkaline-earth-metal elements leads to the highest superconducting critical temperatures (????????). Specifically, Be in ????4, Mg in ????3, and Ca in the kagome bilayer borophene demonstrate superior performance with ???????? reaching up to 58 K. Our study therefore reveals that intercalated bilayer borophene phases are not only more resilient to chemical deterioration, but also harbor enhanced ???????? values compared to their monolayer counterparts, underscoring their substantial potential for the development of boron-based two-dimensional superconductors.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.064803
|
“Imaging the suppression of ferromagnetism in LaMnO₃, by metallic overlayers”. Folkers B, Jansen T, Roskamp TJ, Reith P, Timmermans A, Jannis D, Gauquelin N, Verbeeck J, Hilgenkamp H, Rosario CMM, Physical review materials 8, 054408 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.054408
Abstract: LaMnO 3 (LMO) thin films epitaxially grown on SrTiO 3 (STO) usually exhibit ferromagnetism above a critical layer thickness. We report the use of scanning SQUID microscopy (SSM) to study the suppression of the ferromagnetism in STO / LMO / metal structures. By partially covering the LMO surface with a metallic layer, both covered and uncovered LMO regions can be studied simultaneously. While Au does not significantly influence the ferromagnetic order of the underlying LMO film, a thin Ti layer induces a strong suppression of the ferromagnetism, over tens of nanometers, which increases with time on a timescale of days. Detailed electron energy loss spectroscopy analysis of the Ti-LaMnO 3 interface reveals the presence of Mn 2 + and an evolution of the Ti valence state from Ti 0 to Ti 4 + over approximately 5 nm. Furthermore, we demonstrate that by patterning Ti / Au overlayers, we can locally suppress the ferromagnetism and define ferromagnetic structures down to sub -micrometer scales.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.054408
|
“Multiferroic ScLaX₂, (X = P, As, and Sb) monolayers : bidirectional negative Poisson's ratio effects and phase transformations driven by rare-earth (main-group) elements”. Tian X, Xie X, Li J, Kong X, Gong W-J, Peeters FM, Li L, Physical review materials 8, 084407 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.084407
Abstract: The combination of auxetic property, ferroelasticity, and ferroelectricity in two-dimensional materials offers new avenues for next-generation multifunctional devices. However, two-dimensional materials that simultaneously exhibit those properties are rarely reported. Here, we present a class of two-dimensional Janus-like structures ScLaX2 X 2 (X X = P, As, and Sb) with a rectangular lattice based on first-principles calculations. We predict that those ScLaX2 X 2 monolayers are stable semiconductors with both intrinsic in-plane and out-of-plane auxetic properties, showing a bidirectional negative Poisson's ratio effect. The value of the out-of-plane negative Poisson's ratio effect can reach – 2.28 /- 3.06 /- 3.89. By applying uniaxial strain engineering, two transition paths can be found, including the VA main group element path and the rare-earth metal element path, corresponding to the ferroelastic and the multiferroic (ferroelastic and ferroelectric) phase transition, respectively. For the ScLaSb2 2 monolayer, the external force field can not only control the ferroelastic phase transition, but it can also lead to the reversal of the out-of-plane polarization, exhibiting potential multiferroicity. The coupling between the bidirectional negative Poisson's ratio effect and multiferroicity makes the ScLaX2 X 2 monolayers promising for future device applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.084407
|
“Optical properties of metallic MXene multilayers through advanced first-principles calculations”. Kandemir Z, D'Amico P, Sesti G, Cardoso C, Milošević, MV, Sevik C, Physical review materials 8, 075201 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.075201
Abstract: Having a strong electromagnetic absorption, MXene multilayers are readily envisaged for applications in electromagnetic shields and related prospective technology. However, an ab initio characterization of the optical properties of MXenes is still lacking, due in part to major difficulties with the treatment of metallicity in the first-principles approaches. Here we addressed the latter challenge, after a careful treatment of intraband transitions, to present a thorough analysis of the electronic and optical properties of a selected set of metallic MXene layers based on density functional theory (DFT) and many-body perturbation theory calculations. Our results reveal that the GW corrections are particularly important in regions of the band structure where d and p states hybridize. For some systems, we show that GW corrections open a gap between occupied states, resulting in a band structure that closely resembles that of an intrinsic transparent conductor, thereby opening an additional line of prospective applications for the MXenes family. Nevertheless, GW and Bethe-Salpeter corrections have a minimal influence on the absorption spectra, in contrast to what is typically observed in semiconductor layers. Our present results suggest that calculations within the independent particle approximation (IPA) calculations are sufficiently accurate for assessing the optical characteristics of bulk-layered MXene materials. Finally, our calculated dielectric properties and absorption spectra, in agreement with existing experimental data, confirm the potential of MXenes as effective infrared emitters.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.075201
|
“Strong spin-lattice coupling and high-temperature magnetic ordering in monolayer chromium dichalcogenides”. Gonzalez-Garcia A, Bacaksiz C, Frauenheim T, Milošević, MV, Physical review materials 8, 064001 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.064001
Abstract: We detail the magnetic properties of monolayer CrX2 and its Janus counterparts CrXY (X, Y = S, Se, Te, with X not equal Y) using ab initio methods and Landau-Lifshitz-Gilbert magnetization dynamics, and uncover the pronouncedly strong interplay between their structure symmetry and the magnetic order. The relaxation of nonmagnetic chalcogen atoms, that carry large spin-orbit coupling, changes the energetically preferential magnetic order between in-plane antiferromagnetic and tilted ferromagnetic one. The considered Janus monolayers exhibit sizable Dzyaloshinskii-Moriya interaction, in some cases above 20% of the isotropic exchange, and critical temperature of the long-range magnetic order in the vicinity or even significantly above the room temperature.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.064001
|
“Tuning the quantum phase transition of an ultrathin magnetic topological insulator”. Shafiei M, Fazileh F, Peeters FM, Milošević, MV, Physical review materials 8, 074201 (2024). http://doi.org/10.1103/PHYSREVMATERIALS.8.074201
Abstract: We explore the effect of thickness, magnetization direction, strain, and gating on the topological quantum phase transition of a thin-film magnetic topological insulator. Reducing the film thickness to the ultrathin regime couples the edge states on the two surfaces, opening a gap known as the hybridization gap, and causing a phase transition from a topological insulator to a normal insulator (NI). An out-of-plane/in-plane magnetization of size proportional to the hybridization gap triggers a phase transition from a normal insulator state to a quantum anomalous Hall (QAH)/semimetal state. A magnetization tilt by angle 0 from the out-of-plane axis influences the topological phase transition in a way that for sufficiently large 0, no phase transition from NI to QAH can be observed regardless of the sample thickness or magnetization, and for 0 close to pi /2 the system transits to a semimetal phase. Furthermore, we demonstrate that compressive/tensile strain can be used to decrease/increase the magnetization threshold for the topological phase transition. Finally, we reveal the effect of a vertical potential acting on the film, be it due to the substrate or applied gating, which breaks inversion symmetry and raises the magnetization threshold for the transition from NI to QAH state.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.4
DOI: 10.1103/PHYSREVMATERIALS.8.074201
|
“Computing Curie temperature of two-dimensional ferromagnets in the presence of exchange anisotropy”. Tiwari S, Vanherck J, Van de Put ML, Vandenberghe WG, Sorée B, Physical review research 3, 043024 (2021). http://doi.org/10.1103/PHYSREVRESEARCH.3.043024
Abstract: We compare three first-principles methods of calculating the Curie temperature in two-dimensional (2D) ferromagnetic materials (FM), modeled using the Heisenberg model, and propose a simple formula for estimating the Curie temperature with high accuracy that works for all common 2D lattice types. First, we study the effect of exchange anisotropy on the Curie temperature calculated using the Monte Carlo (MC), the Green's function, and the renormalized spin-wave (RNSW) methods. We find that the Green's function method overestimates the Curie temperature in high-anisotropy regimes compared to the MC method, whereas the RNSW method underestimates the Curie temperature compared to the MC and the Green's function methods. Next, we propose a closed-form formula for calculating the Curie temperature of 2D FMs, which provides an estimate of the Curie temperature that is greatly improved over the mean-field expression for magnetic material screening. We apply the closed-form formula to predict the Curie temperature 2D magnets screened from the C2DB database and discover several high Curie temperature FMs, with Fe2F2 and MoI2 emerging as the most promising 2D ferromagnets. Finally, by comparing to experimental results for CrI3, CrCl3, and CrBr3, we conclude that for small effective anisotropies, the Green's-function-based equations are preferable, while for larger anisotropies, MC-based results are more predictive.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1103/PHYSREVRESEARCH.3.043024
|
“In-gap band in the one-dimensional two-orbital Kanamori-Hubbard model with interorbital Coulomb interaction”. Aucar Boidi N, Fernández García H, Nunez-Fernandez Y, Hallberg K, Physical review research 3, 043213 (2021). http://doi.org/10.1103/PHYSREVRESEARCH.3.043213
Abstract: We study the electronic spectral properties at zero temperature of the one-dimensional (1D) version of the degenerate two-orbital Kanamori-Hubbard model, one of the well-established frameworks to study transition metal compounds, using state-of-the-art numerical techniques based on the density matrix renormalization group. While the system is Mott insulating for the half-filled case, as expected for an interacting 1D system, we find interesting and rich structures in the single-particle density of states (DOS) for the hole-doped system. In particular, we find the existence of in-gap states which are pulled down to lower energies from the upper Hubbard band with increasing the interorbital Coulomb interaction V. We analyze the composition of the DOS by projecting it onto different local excitations, and we observe that for large dopings these in-gap excitations are formed mainly by interorbital holon-doublon (HD) states and their energies follow approximately the HD states in the atomic limit. We observe that the Hund interaction J increases the width of the in-gap band, as expected from the two-particle fluctuations in the Hamiltonian. The observation of a finite density of states within the gap between the Hubbard bands for this extended 1D model indicates that these systems present a rich excitation spectra which could help us understand the microscopic physics behind multiorbital compounds.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Antwerp X-ray Imaging and Spectroscopy (AXIS)
DOI: 10.1103/PHYSREVRESEARCH.3.043213
|
“2D semiconductors at the Leuven pulsed field facility”. Bogaerts R, de Keyser A, van Bockstal L, van der Burgt M, van Esch A, Provoost R, Silverans R, Herlach F, Swinnen B, van de Stadt AFW, Koenraad PM, Wolter JH, Karavolas VC, Peeters FM, van de Graaf W, Borghs G, Physicalia magazine 19, 229 (1997)
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
|
“Artificial atoms and molecules”. Partoens B, Peeters FM, Physicalia magazine 24, 29 (2002)
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
|
“Oppervlakte en in-diepte analyse via SIMS, SNMS en GDMS”. Gijbels R, Physicalia magazine 14, 49 (1992)
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
|
“Probing of the electron-phonon interaction using high magnetic fields”. Peeters FM, Physicalia magazine 19, 187 (1997)
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
|
“Single and coupled type II quantum dots in magnetic and electric fields”. Janssens KL, Partoens B, Peeters FM, Physicalia magazine 24, 211 (2002)
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
|
“Vortex-antivortex ionic crystals in superconducting films with magnetic pinning arays”. Milošević, MV, Peeters FM, Physicalia magazine 26, 355 (2004)
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
|