“Accurate and Robust Calibration of the Uniform Affine Transformation Between Scan-Camera Coordinates for Atom-Resolved In-Focus 4D-STEM Datasets”. Ning S, Xu W, Ma Y, Loh L, Pennycook TJ, Zhou W, Zhang F, Bosman M, Pennycook SJ, He Q, Loh ND, Microscopy and microanalysis , 1 (2022). http://doi.org/10.1017/S1431927622000320
Abstract: Accurate geometrical calibration between the scan coordinates and the camera coordinates is critical in four-dimensional scanning transmission electron microscopy (4D-STEM) for both quantitative imaging and ptychographic reconstructions. For atomic-resolved, in-focus 4D-STEM datasets, we propose a hybrid method incorporating two sub-routines, namely a J-matrix method and a Fourier method, which can calibrate the uniform affine transformation between the scan-camera coordinates using raw data, without a priori knowledge about the crystal structure of the specimen. The hybrid method is found robust against scan distortions and residual probe aberrations. It is also effective even when defects are present in the specimen, or the specimen becomes relatively thick. We will demonstrate that a successful geometrical calibration with the hybrid method will lead to a more reliable recovery of both the specimen and the electron probe in a ptychographic reconstruction. We will also show that, although the elimination of local scan position errors still requires an iterative approach, the rate of convergence can be improved, and the residual errors can be further reduced if the hybrid method can be firstly applied for initial calibration. The code is made available as a simple-to-use tool to correct affine transformations of the scan-camera coordinates in 4D-STEM experiments.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.8
DOI: 10.1017/S1431927622000320
|
“Optical absorption window in Na₃Bi based three-dimensional Dirac electronic system”. Li QN, Xu W, Xiao YM, Ding L, Van Duppen B, Peeters FM, Journal Of Applied Physics 128, 155707 (2020). http://doi.org/10.1063/5.0022669
Abstract: We present a detailed theoretical study of the optoelectronic properties of a Na3Bi based three-dimensional Dirac electronic system (3DDES). The optical conductivity is evaluated using the energy-balance equation derived from a Boltzmann equation, where the electron Hamiltonian is taken from a simplified k . p approach. We find that for short-wavelength irradiation, the optical absorption in Na3Bi is mainly due to inter-band electronic transitions. In contrast to the universal optical conductance observed for graphene, the optical conductivity for Na3Bi based 3DDES depends on the radiation frequency but not on temperature, carrier density, and electronic relaxation time. In the radiation wavelength regime of about 5 mu m, < lambda < 200 mu m, an optical absorption window is found. This is similar to what is observed in graphene. The position and width of the absorption window depend on the direction of the light polarization and sensitively on temperature, carrier density, and electronic relaxation time. Particularly, we demonstrate that the inter-band optical absorption channel can be switched on and off by applying the gate voltage. This implies that similar to graphene, Na3Bi based 3DDES can also be applied in infrared electro-optical modulators. Our theoretical findings are helpful in gaining an in-depth understanding of the basic optoelectronic properties of recently discovered 3DDESs.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.2
Times cited: 1
DOI: 10.1063/5.0022669
|
“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
|
“Normal and hot electro-phonon resonance effect in a quasi-two-dimensional semiconductor system”. Xu W, Peeters FM, Devreese JT, Journal of physics : condensed matter 5, 2307 (1993). http://doi.org/10.1088/0953-8984/5/15/004
Abstract: The electro-phonon resonance effect is a consequence of a resonant interaction between two electric subbands mediated by an optical phonon. It occurs in a quasi-two-dimensional electron system each time the energy difference between two electric subbands equals the energy of a Lo phonon. We study the influence of this effect on the electron mobility by using the momentum balance equation. The temperature and electron density dependences of the resonances are studied in the linear and non-linear response regimes.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Impact Factor: 2.346
Times cited: 18
DOI: 10.1088/0953-8984/5/15/004
|
“Terahertz magneto-optical properties of bi- and tri-layer graphene”. Mei H, Xu W, Wang C, Yuan H, Zhang C, Ding L, Zhang J, Deng C, Wang Y, Peeters FM, Journal of physics : condensed matter 30, 175701 (2018). http://doi.org/10.1088/1361-648X/AAB81D
Abstract: Magneto-optical (MO) properties of bi- and tri-layer graphene are investigated utilizing terahertz time-domain spectroscopy (THz TDS) in the presence of a strong magnetic field at room-temperature. In the Faraday configuration and applying optical polarization measurements, we measure the real and imaginary parts of the longitudinal and transverse MO conductivities of different graphene samples. The obtained experimental data fits very well with the classical MO Drude formula. Thus, we are able to obtain the key sample and material parameters of bi- and tri-layer graphene, such as the electron effective mass, the electronic relaxation time and the electron density. It is found that in high magnetic fields the electronic relaxation time tau for bi- and tri-layer graphene increases with magnetic field B roughly in a form tau similar to B-2. Most importantly, we obtain the electron effective mass for bi- and tri-layer graphene at room-temperature under non-resonant conditions. This work shows how the advanced THz MO techniques can be applied for the investigation into fundamental physics properties of atomically thin 2D electronic systems.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 11
DOI: 10.1088/1361-648X/AAB81D
|
“Electric-field modulation of linear dichroism and Faraday rotation in few-layer phosphorene”. Li LL, Partoens B, Xu W, Peeters FM, 2D materials 6, 015032 (2019). http://doi.org/10.1088/2053-1583/AAF47F
Abstract: Electro-optical modulators, which use an electric voltage (or an electric field) to modulate a beam of light, are essential elements in present-day telecommunication devices. Using a self-consistent tight-binding approach combined with the standard Kubo formula, we show that the optical conductivity and the linear dichroism of few-layer phosphorene can be modulated by a perpendicular electric field. We find that the field-induced charge screening plays a significant role in modulating the optical conductivity and the linear dichroism. Distinct absorption peaks are induced in the conductivity spectrum due to the strong quantum confinement along the out-of-plane direction and to the field-induced forbidden-to-allowed transitions. The field modulation of the linear dichroism becomes more pronounced with increasing number of phosphorene layers. We also show that the Faraday rotation is present in few-layer phosphorene even in the absence of an external magnetic field. This optical Hall effect is induced by the reduced lattice symmetry of few-layer phosphorene. The Faraday rotation is greatly influenced by the field-induced charge screening and is strongly dependent on the strength of perpendicular electric field and on the number of phosphorene layers.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.937
Times cited: 23
DOI: 10.1088/2053-1583/AAF47F
|
“Terahertz optical Hall effect in monolayer MoS₂, in the presence of proximity-induced interactions”. Zhao XN, Xu W, Xiao YM, Liu J, Van Duppen B, Peeters FM, Physical Review B 101, 245412 (2020). http://doi.org/10.1103/PHYSREVB.101.245412
Abstract: The effect of proximity-induced interactions such as Rashba spin-orbit coupling (SOC) and exchange interaction on the electronic and optical properties of n-type monolayer (ML) MoS2 is investigated. We predict and demonstrate that the Rashba SOC can induce an in-plane spin splitting with terahertz (THz) energy, while the exchange interaction lifts the energy degeneracy in different valleys. Thus, spin polarization can be achieved in an n-type ML MoS2 and valley Hall or optical Hall effect can be observed using linearly polarized THz radiation. In such a case, the transverse optical conductivity sigma(xy) (omega) results from spin-flip transition within spin-split conduction bands and from the fact that contributions from electrons with different spin orientations in different valleys can no longer be canceled out. Interestingly, we find that for fixed effective Zeeman field (or exchange interaction) the lowest spin-split conduction band in ML MoS2 can be tuned from one in the K valley to another one in the K' valley by varying the Rashba parameter lambda(R). Therefore, by changing lambda(R) we can turn the sign of the spin polarization and Im sigma(xy) (omega) from positive to negative. Moreover, we find that the dominant contribution of the selection rules to sigma(xx)(omega) is from electrons in the K valley and to sigma(xy) (omega) is from electrons in the K' valley. These important and interesting theoretical findings can be helpful to experimental observation of the optical Hall effect in valleytronic systems using linearly polarized THz radiation fields.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 8
DOI: 10.1103/PHYSREVB.101.245412
|
“Terahertz magneto-optical properties of graphene hydrodynamic electron liquid”. Man LF, Xu W, Xiao YM, Wen H, Ding L, Van Duppen B, Peeters FM, Physical Review B 104, 125420 (2021). http://doi.org/10.1103/PHYSREVB.104.125420
Abstract: The discovery of the hydrodynamic electron liquid (HEL) in graphene [D. Bandurin et al., Science 351, 1055 (2016) and J. Crossno et al., Science 351, 1058 (2016)] has marked the birth of the solid-state HEL which can be probed near room temperature in a table-top setup. Here we examine the terahertz (THz) magneto-optical (MO) properties of a graphene HEL. Considering the case where the magnetic length l(B) = root h/eB is comparable to the mean-free path l(ee) for electron-electron interaction in graphene, the MO conductivities are obtained by taking a momentum balance equation approach on the basis of the Boltzmann equation. We find that when l(B) similar to l(ee), the viscous effect in a HEL can weaken significantly the THz MO effects such as cyclotron resonance and Faraday rotation. The upper hybrid and cyclotron resonance magnetoplasmon modes omega(+/-) are also obtained through the RPA dielectric function. The magnetoplasmons of graphene HEL at large wave-vector regime are affected by the viscous effect, and results in red-shifts of the magnetoplasmon frequencies. We predict that the viscosity in graphene HEL can affect strongly the magneto-optical and magnetoplasmonic properties, which can be verified experimentally.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 4
DOI: 10.1103/PHYSREVB.104.125420
|
“Anisotropic and tunable optical conductivity of a two-dimensional semi-Dirac system in the presence of elliptically polarized radiation”. Zhang HY, Xiao YM, N Li Q, Ding L, Van Duppen B, Xu W, Peeters FM, Physical review B 105, 115423 (2022). http://doi.org/10.1103/PHYSREVB.105.115423
Abstract: We investigate the effect of ellipticity ratio of the polarized radiation field on optoelectronic properties of a two-dimensional (2D) semi-Dirac (SD) system. The optical conductivity is calculated within the energy balance equation approach derived from the semiclassical Boltzmann equation. We find that there exists the anisotropic optical absorption induced via both the intra-and interband electronic transition channels in the perpendicular xx and yy directions. Furthermore, we examine the effects of the ellipticity ratio, the temperature, the carrier density, and the band-gap parameter on the optical conductivity of the 2D SD system placed in transverse and vertical directions, respectively. It is shown that the ellipticity ratio, temperature, carrier density, and band-gap parameter can play the important roles in tuning the strength, peak position, and shape of the optical conductivity spectrum. The results obtained from this study indicate that the 2D SD system can be a promising anisotropic and tunable optical and optoelectronic material for applications in innovative 2D optical and optoelectronic devices, which are active in the infrared and terahertz bandwidths.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 3
DOI: 10.1103/PHYSREVB.105.115423
|
“Streaming-to-accumulation transition in a 2-dimensional electron-system in a polar semiconductor”. Xu W, Peeters FM, Devreese JT, Physical review : B : condensed matter and materials physics 46, 7571 (1992). http://doi.org/10.1103/PhysRevB.46.7571
Abstract: Hot-electron transport is studied for a two-dimensional electron gas coupled to longitudinal-optical phonons in crossed electric and magnetic fields. At low electric and high magnetic fields the electrons are accumulated, while at high electric fields they are in a streaming state. We develop a streaming-to-accumulation transition model and compare the results with that from a Monte Carlo simulation.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Impact Factor: 3.736
Times cited: 13
DOI: 10.1103/PhysRevB.46.7571
|
“Electrophonon resonances in a quasi-two-dimensional electron system”. Xu W, Peeters FM, Devreese JT, Physical review : B : condensed matter and materials physics 48, 1562 (1993). http://doi.org/10.1103/PhysRevB.48.1562
Abstract: When the energy difference between two electric subbands in a quasi-two-dimensional electron system equals a LO-phonon energy, resonant scattering will occur. This leads to an enhancement of the scattering rate and, consequently, to a suppression of the conductivity. Changing the energy difference between the electric subbands (e.g., through a gate) leads to a series of electrophonon resonances in the conductivity. A detailed study is made of this effect for different confinement potentials. We found that the scattering processes where the emission of a phonon is involved are very important for the electrophonon resonance and that the size of the effect decreases with increasing temperature.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Impact Factor: 3.736
Times cited: 45
DOI: 10.1103/PhysRevB.48.1562
|
“Quantum and transport conductivities in monolayer graphene”. Dong HM, Xu W, Zeng Z, Lu TC, Peeters FM, Physical review : B : condensed matter and materials physics 77, 235402 (2008). http://doi.org/10.1103/PhysRevB.77.235402
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 31
DOI: 10.1103/PhysRevB.77.235402
|
“Dependence of resistivity on electron density and temperature in graphene”. Xu W, Peeters FM, Lu TC, Physical review : B : solid state 79, 073403 (2009). http://doi.org/10.1103/PhysRevB.79.073403
Abstract: On the basis of the momentum-balance equation derived from the Boltzmann equation in which electron interactions with impurities and acoustic and optic phonons are included, we examine the dependence of the resistivity in graphene on temperature and electron density. Simple analytical expressions for the different contributions to the resistivity are obtained. Our results reproduce recent experimental findings and we are able to understand the different temperature dependence of the resistivity for low and high density samples.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 31
DOI: 10.1103/PhysRevB.79.073403
|
“Landau-level broadening due to electron-impurity interaction in graphene in strong magnetic fields”. Yang CH, Peeters FM, Xu W, Physical review : B : condensed matter and materials physics 82, 075401:1 (2010). http://doi.org/10.1103/PhysRevB.82.075401
Abstract: The effect of electron-impurity and electron-electron interactions on the energy spectrum of electrons moving in graphene is investigated in the presence of a high magnetic field. We find that the width of the broadened Landau levels exhibits an approximate 1/B dependence near half filling for charged impurity scattering. The Landau-level width, the density of states, and the Fermi energy exhibit an oscillatory behavior as a function of magnetic field. Comparison with experiment shows that scattering with charged impurities cannot be the main scattering mechanism that determines the width of the Landau levels.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 38
DOI: 10.1103/PhysRevB.82.075401
|
“Optoelectronic properties of graphene in the presence of optical phonon scattering”. Xu W, Dong HM, Li LL, Yao JQ, Vasilopoulos P, Peeters FM, Physical review : B : condensed matter and materials physics 82, 125304 (2010). http://doi.org/10.1103/PhysRevB.82.125304
Abstract: We study in detail the optoelectronic properties of graphene. Considering the electron interactions with photons and phonons, we employ the mass- and energy-balance equations to self-consistently evaluate the photoinduced carrier densities, the optical conductance, and the transmission coefficient in the presence of a linearly polarized radiation field. We demonstrate that the photoinduced carrier densities increase around the electron-photon-phonon resonant transition. They depend strongly on the radiation intensity and frequency, temperature, and dark carrier density. For short-wavelength radiation (L<3 μm), we obtain the universal optical conductance σ0=e2/(4ℏ). Importantly, there exists an optical-absorption window in the radiation wavelength range 4100 μm, which is induced by different transition energies required for interband and intraband optical absorption. The position and width of this window depend sensitively on the temperature and the carrier density of the system. These theoretical results are in line with recent experimental findings and indicate that graphene exhibits important features not only in the visible regime but also in the midinfrared bandwidth.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 28
DOI: 10.1103/PhysRevB.82.125304
|
“Density of states and magneto-optical conductivity of graphene in a perpendicular magnetic field”. Yang CH, Peeters FM, Xu W, Physical review : B : condensed matter and materials physics 82, 205428 (2010). http://doi.org/10.1103/PhysRevB.82.205428
Abstract: The density of states (DOS) and the optical conductivity of graphene is calculated in the presence of a perpendicular magnetic field and where scattering on charged and short-range impurities is included. The standard Kubo formula is employed where the self-energy induced by impurity scattering and the Green's function are calculated self-consistently including inter-Landau level (LL) coupling and screening effects. It is found that the scattering from those two types of impurities results in a symmetric LL broadening and asymmetric inter-LL coupling renormalizes the LL positions to lower energy. The peak position and intensity of the magneto-optical conductivity depends on the filling factor and the broadened DOS. Good agreement is found with recent cyclotron resonance measurements.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 39
DOI: 10.1103/PhysRevB.82.205428
|
“Intrinsic optical anisotropy of [001]-grown short-period InAs/GaSb superlattices”. Li LL, Xu W, Peeters FM, Physical review : B : condensed matter and materials physics 82, 235422 (2010). http://doi.org/10.1103/PhysRevB.82.235422
Abstract: We theoretically investigate the intrinsic optical anisotropy or polarization induced by the microscopic interface asymmetry (MIA) in no-common-atom (NCA) InAs/GaSb superlattices (SLs) grown along the [001] direction. The eight-band K⋅P model is used to calculate the electronic band structures and incorporates the MIA effect. A Boltzmann equation approach is employed to calculate the optical properties. We found that in NCA InAs/GaSb SLs, the MIA effect causes a large in-plane optical anisotropy for linearly polarized light and the largest anisotropy occurs for light polarized along the [110] and [11̅ 0] directions. The relative difference between the optical-absorption coefficient for [110]-polarized light and that for [11̅ 0]-polarized light is found to be larger than 50%. The dependence of the in-plane optical anisotropy on temperature, photoexcited carrier density, and layer width is examined in detail. This study is important for optical devices which require the polarization control and selectivity.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 18
DOI: 10.1103/PhysRevB.82.235422
|
“Piezoelectric surface acoustical phonon limited mobility of electrons in graphene on a GaAs substrate”. Zhang SH, Xu W, Badalyan SM, Peeters FM, Physical review : B : condensed matter and materials physics 87, 075443 (2013). http://doi.org/10.1103/PhysRevB.87.075443
Abstract: We study the mobility of Dirac fermions in monolayer graphene on a GaAs substrate, limited by the combined action of the extrinsic potential of piezoelectric surface acoustical phonons of GaAs (PA) and of the intrinsic deformation potential of acoustical phonons in graphene (DA). In the high-temperature (T) regime, the momentum relaxation rate exhibits the same linear dependence on T but different dependencies on the carrier density n, corresponding to the mobility mu proportional to 1 root n and 1/n, respectively for the PA and DA scattering mechanisms. In the low-T Bloch-Gruneisen regime, the mobility shows the same square-root density dependence mu proportional to root n, but different temperature dependencies mu proportional to T-3 and T-4, respectively for PA and DA phonon scattering. DOI: 10.1103/PhysRevB.87.075443
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 25
DOI: 10.1103/PhysRevB.87.075443
|
“Electron energy and temperature relaxation in graphene on a piezoelectric substrate”. Zhang SH, Xu W, Peeters FM, Badalyan SM, Physical review : B : condensed matter and materials physics 89, 195409 (2014). http://doi.org/10.1103/PhysRevB.89.195409
Abstract: We study the energy and temperature relaxation of electrons in graphene on a piezoelectric substrate. Scattering from the combined potential of extrinsic piezoelectric surface acoustical (PA) phonons of the substrate and intrinsic deformation acoustical phonons of graphene is considered for a (non) degenerate gas of Dirac fermions. It is shown that in the regime of low energies or temperatures the PA phonons dominate the relaxation and change qualitatively its character. This prediction is relevant for quantum metrology and electronic applications using graphene devices and suggests an experimental setup for probing electron-phonon coupling in graphene.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 18
DOI: 10.1103/PhysRevB.89.195409
|
“Plasmon and coupled plasmon-phonon modes in graphene in the presence of a driving electric field”. Zhao CX, Xu W, Dong HM, Peeters FM, Physical review : B : condensed matter and materials physics 89, 195447 (2014). http://doi.org/10.1103/PhysRevB.89.195447
Abstract: We present a theoretical study of the plasmon and coupled plasmon-phonon modes induced by intraband electron-electron interaction in graphene in the presence of driving dc electric field. We find that the electric field dependence of these collective excitation modes in graphene differs significantly from that in a conventional two-dimensional electron gas with a parabolic energy spectrum. This is due mainly to the fact that graphene has a linear energy spectrum and the Fermi velocity of electrons in graphene is much larger than the drift velocity of electrons. The obtained results demonstrate that the plasmon and coupled plasmon-phonon modes in graphene can be tuned by applying not only the gate voltage but also the source-to-drain field. The manipulation of plasmon and coupled plasmon-phonon modes by source-to-drain voltage can let graphene be more conveniently applied as an advanced plasmonic material.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 9
DOI: 10.1103/PhysRevB.89.195447
|
“Infrared to terahertz optical conductivity of n-type and p-type monolayer MoS2 in the presence of Rashba spin-orbit coupling”. Xiao YM, Xu W, Van Duppen B, Peeters FM, Physical review B 94, 155432 (2016). http://doi.org/10.1103/PHYSREVB.94.155432
Abstract: We investigate the effect of Rashba spin-orbit coupling (SOC) on the optoelectronic properties of n- and p-type monolayer MoS2. The optical conductivity is calculated within the Kubo formalism. We find that the spin-flip transitions enabled by the Rashba SOC result in a wide absorption window in the optical spectrum. Furthermore, we evaluate the effects of the polarization direction of the radiation, temperature, carrier density, and the strength of the Rashba spin-orbit parameter on the optical conductivity. We find that the position, width, and shape of the absorption peak or absorption window can be tuned by varying these parameters. This study shows that monolayer MoS2 can be a promising tunable optical and optoelectronic material that is active in the infrared to terahertz spectral range.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 20
DOI: 10.1103/PHYSREVB.94.155432
|
“Exciton states in a circular graphene quantum dot: Magnetic field induced intravalley to intervalley transition”. Li LL, Zarenia M, Xu W, Dong HM, Peeters FM, Physical review B 95, 045409 (2017). http://doi.org/10.1103/PHYSREVB.95.045409
Abstract: The magnetic-field dependence of the energy spectrum, wave function, binding energy, and oscillator strength of exciton states confined in a circular graphene quantum dot (CGQD) is obtained within the configuration interaction method. We predict that (i) excitonic effects are very significant in the CGQD as a consequence of a combination of geometric confinement, magnetic confinement, and reduced screening; (ii) two types of excitons (intravalley and intervalley) are present in the CGQD because of the valley degree of freedom in graphene; (iii) the intravalley and intervalley exciton states display different magnetic-field dependencies due to the different electron-hole symmetries of the single-particle energy spectra; (iv) with increasing magnetic field, the exciton ground state in the CGQD undergoes an intravalley to intervalley transition accompanied by a change of angular momentum; (v) the exciton binding energy does not increase monotonically with the magnetic field due to the competition between geometric and magnetic confinements; and (vi) the optical transitions of the intervalley and intravalley excitons can be tuned by the magnetic field, and valley-dependent excitonic transitions can be realized in a CGQD.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 14
DOI: 10.1103/PHYSREVB.95.045409
|
“Electronic and transport properties of n-type monolayer black phosphorus at low temperatures”. Han FW, Xu W, Li LL, Zhang C, Dong HM, Peeters FM, Physical review B 95, 115436 (2017). http://doi.org/10.1103/PhysRevB.95.115436
Abstract: We present a detailed theoretical study of the electronic and transport properties of monolayer black phosphorus (BP). This study is motivated by recent experimental activities in investigating n-type few-layer BP systems. The electron density of states, the screening length, and the low-temperature electron mobility are calculated for monolayer BP (MLBP). In particular, the electron transport mobilities along the armchair and zigzag directions are examined on the basis of the momentum-balance equation derived from a semiclassical Boltzmann equation. The anisotropic electron mobilities in MLBP along different directions are demonstrated where the electron-impurity scattering is considered. Furthermore, we compare the results obtained from two electronic band structures of MLBP and find that the simplified model can describe quite rightly the electronic and transport properties of MLBP. This study is relevant to the application of few-layer BP based electronic systems as advanced electronic devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 12
DOI: 10.1103/PhysRevB.95.115436
|
“Multicomponent plasmons in monolayer MoS2 with circularly polarized optical pumping”. Xiao YM, Xu W, Peeters FM, Van Duppen B, Physical review B 96, 085405 (2017). http://doi.org/10.1103/PHYSREVB.96.085405
Abstract: By making use of circularly polarized light and electrostatic gating, monolayer molybdenum disulfide (ML – MoS2) can form a platform supporting multiple types of charge carriers. They can be discriminated by their spin, valley index, or whether they are electrons or holes. We investigate the collective properties of those charge carriers and are able to identify distinct plasmon modes. We analyze the corresponding dispersion relation, lifetime, and oscillator strength, and calculate the phase relation between the oscillations in the different components of the plasmon modes. All platforms in ML-MoS2 support a long-wavelength root q plasmon branch at zero kelvins. In addition to this, for an n-component system, n-1 distinct plasmon modes appear as acoustic modes with linear dispersion in the long-wavelength limit. These modes correspond to out-of-phase oscillations in the different fermion liquids and have, although being damped, a relatively long lifetime. Additionally, we also find distinct modes at large wave vectors that are more strongly damped by intraband processes.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 2
DOI: 10.1103/PHYSREVB.96.085405
|
“Electronic properties of bilayer phosphorene quantum dots in the presence of perpendicular electric and magnetic fields”. Li LL, Moldovan D, Xu W, Peeters FM, Physical review B 96, 155425 (2017). http://doi.org/10.1103/PHYSREVB.96.155425
Abstract: Using the tight-binding approach, we investigate the electronic properties of bilayer phosphorene (BLP) quantum dots (QDs) in the presence of perpendicular electric and magnetic fields. Since BLP consists of two coupled phosphorene layers, it is of interest to examine the layer-dependent electronic properties of BLP QDs, such as the electronic distributions over the two layers and the so-produced layer-polarization features, and to see how these properties are affected by the magnetic field and the bias potential. We find that in the absence of a bias potential only edge states are layer polarized while the bulk states are not, and the layer-polarization degree (LPD) of the unbiased edge states increases with increasing magnetic field. However, in the presence of a bias potential both the edge and bulk states are layer polarized, and the LPD of the bulk (edge) states depends strongly (weakly) on the interplay of the bias potential and the interlayer coupling. At high magnetic fields, applying a bias potential renders the bulk electrons in a BLP QD to be mainly distributed over the top or bottom layer, resulting in layer-polarized bulk Landau levels (LLs). In the presence of a large bias potential that can drive a semiconductor-to-semimetal transition in BLP, these bulk LLs exhibit different magnetic-field dependences, i.e., the zeroth LLs exhibit a linearlike dependence on the magnetic field while the other LLs exhibit a square-root-like dependence.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 28
DOI: 10.1103/PHYSREVB.96.155425
|
“Quantum and transport mobilities of a Na3Bi-based three-dimensional Dirac system”. Yuan HF, Xu W, Zhao XN, Song D, Zhang GR, Xiao YM, Ding L, Peeters FM, Physical review B 99, 235303 (2019). http://doi.org/10.1103/PHYSREVB.99.235303
Abstract: The electronic and transport properties of a three-dimensional (3D) Dirac system are investigated theoretically, which is motivated by recent experimental measurements on quantum and transport mobilities in the 3D Dirac semimetal Na3Bi by J. Xiong et al. [Science 350, 413 (2015); Europhys. Lett. 114, 27002 (2016)]. The electron Hamiltonian is taken from a simplified k center dot p approach. From the obtained electronic band structure and the Fermi energy, we explain why the anomalous effect induced by the chiral anomaly and the Berry curvature in the energy band can be observed experimentally in magnetotransport coefficients in both low-and high-density samples. Moreover, the quantum and transport mobilities are calculated on the basis of the momentum-balance equation derived from a semiclassical Boltzmann equation with the electron-impurity interaction. The quantum and transport mobilities obtained from this study agree both qualitatively and quantitatively with those measured experimentally. We also examine the electron mobilities along different crystal directions in Na3Bi and find them largely anisotropic. The theoretical findings from this work can be helpful in gaining an in-depth understanding of the experimental results and of the basic electronic and transport properties of newly developed 3D Dirac systems.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 3
DOI: 10.1103/PHYSREVB.99.235303
|
“Photoluminescence and electronic transition behaviors of single-stranded DNA”. Wang Q, Lin S, Liu X, Xu W, Xiao Y, Liang C, Ding L, Peeters FM, Physical Review E 104, 034412 (2021). http://doi.org/10.1103/PHYSREVE.104.034412
Abstract: Due to the potential application of DNA for biophysics and optoelectronics, the electronic energy states and transitions of this genetic material have attracted a great deal of attention recently. However, the fluorescence and corresponding physical process of DNA under optical excitation with photon energies below ultraviolet are still not fully clear. In this work, we experimentally investigate the photoluminescence (PL) properties of single-stranded DNA (ssDNA) samples under near-ultraviolet (NUV) and visible excitations (270 similar to 440 nm). Based on the dependence of the PL peak wavelength (lem) upon the excitation wavelength (lex), the PL behaviors of ssDNA can be approximately classified into two categories. In the relatively short excitation wavelength regime, lem is nearly constant due to exciton-like transitions associated with delocalized excitonic states and excimer states. In the relatively long excitation wavelength range, a linear relation of lem = Alex + B with A 0 or A < 0 can be observed, which comes from electronic transitions related to coupled vibrational-electronic levels. Moreover, the transition channels in different excitation wavelength regimes and the effects of strand length and base type can be analyzed on the basis of these results. These important findings not only can give a general description of the electronic energy states and transitional behaviors of ssDNA samples under NUV and visible excitations, but also can be the basis for the application of DNA in nanoelectronics and optoelectronics.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
DOI: 10.1103/PHYSREVE.104.034412
|
“Collapse of high field magnetophonon resonance in GaAs-GaAlAs heterojunctions”. Leadley DR, Nicholas RJ, Singleton J, Xu W, Peeters FM, Devreese JT, Perenboom JAAJ, van Bockstal L, Herlach F, Harris JJ, Foxon CT, Physical review letters 73, 589 (1994). http://doi.org/10.1103/PhysRevLett.73.589
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Impact Factor: 7.512
Times cited: 24
DOI: 10.1103/PhysRevLett.73.589
|
“Spin polarization in monolayer MoS₂, in the presence of proximity-induced interactions”. Zhao XN, Xu W, Xiao YM, Van Duppen B, International Journal Of Modern Physics C 31, 2050143 (2020). http://doi.org/10.1142/S0129183120501430
Abstract: When monolayer (ML) MoS2 is placed on a substrate, the proximity-induced interactions such as the Rashba spin-orbit coupling (RSOC) and exchange interaction (EI) can be introduced. Thus, the electronic system can behave like a spintronic device. In this study, we present a theoretical study on how the presence of the RSCO and EI can lead to the band splitting, the lifting of the valley degeneracy and to the spin polarization in n- and p-type ML MoS2. We find that the maxima of the in-plane spin orientation in the conduction and valence bands in ML MoS2 depend on the Rashba parameter and the effective Zeeman field factor. At a fixed Rashba parameter, the minima of the split conduction band and the maxima of the split valence band along with the spin polarization in ML MoS2 can be tuned effectively by varying the effective Zeeman field factor. On the basis that the EI can be induced by placing the ML MoS2 on a ferromagnetic substrate or by magnetic doping in ML MoS2, we predict that the interesting spintronic effects can be observed in n- and p-type ML MoS2. This work can be helpful to gain an in-depth understanding of the basic physical properties of ML MoS2 for application in advanced electronic and optoelectronic devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.9
DOI: 10.1142/S0129183120501430
|
“Electrical generation of terahertz blackbody radiation from graphene”. Dong HM, Xu W, Peeters FM, Optics express 26, 24621 (2018). http://doi.org/10.1364/OE.26.024621
Abstract: Recent experimental work on the application of graphene for novel illumination motivated us to present a theoretical study of the blackbody radiation emission from a freely suspended graphene driven by a dc electric field. Strong terahertz (THz) emission, with intensity up to mW/cm(2), can be generated with increasing electric field strength due to the heating of electrons in graphene. We show that the intensity of the THz emission generated electrically from graphene depends rather sensitively on the lattice temperature in relatively weak electric fields, whereas it is less sensitive to the lattice temperature in relative strong electric fields. Our study highlights the practical application of graphene as intense THz source where the radiation is generated electrically. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.307
Times cited: 14
DOI: 10.1364/OE.26.024621
|