arXiv subjects

Chen-Huan Wu

Publications and source records attributed to Chen-Huan Wu.

At least 37 records · Page 2Linked to original sources

arXiv2020

Attractive polaron formed in doped nonchiral/chiral parabolic system within ladder approximation

We investigate the properties of attractive polaron formed by a single impurity dressed with the particle-hole excitations in a three-dimensional (3D) doped (extrinsic) parabolic system. %at zero-temperature limit. Base on the single particle-hole variational ansatz, we study the pair propagator, self-energy, and the non-self-consistent medium $T$-matrix. The non-self-consistent $T$-matrix discussed in this paper contains only the open channel since we don't consider the shift of center-of-mass due to the resonance (e.g., induced by the magnetic field). Besides, since we focus on the low-density regime of the majority particles, the effective Fermi wave vector is small. The scattering form factor is discussed in detail for the chiral case and compared to the non-chiral one. The effects of the bare coupling strength, which is momentum-cutoff-dependent, are also discussed. %within the pair propagator due to the scattering %with a certain scattering angle. We found that the pair propagator and the related quantities, like the self-energy, spectral function, induced effective mass, and residue (spectral weight), all exhibit different features in the low-momentum regime and the high one, which also related to the polaronic instabilities as well as the many-body fluctuation and nonadiabatic/adiabatic dynamics. The pair-propagator and the energy relaxation time at finite temperature are also explored.

cond-mat.quant-gas↗

arXiv2019

Electronic properties and polaronic dynamics of semi-Dirac system within ladder approximation

We investigate the electronic properties of the semi-Dirac system and its polaronic dynamics when coupled with a fermi bath with quadratic dispersion. The electronic anisotropic transport properties and the semiclassical dynamics of the semi-Dirac system are studied, including the density-of-states, conductivity, transport relaxation rate, specific heat, electrical current denity, and free energy. The attractive polaron formed as the semi-Dirac impurity dressed with the particle-hole excitations in a two-dimensional system are studied both analytically and numerically. The pair propagator, self-energy, spectral function are being detailly calculated and discussed.

cond-mat.quant-gas↗

arXiv2019

Electronic properties of the Dirac and Weyl systems with first- and higher-order dispersion in non-Fermi-liquid picture

We investigate the non-Fermi-liquid behaviors of the 2D and 3D Dirac/Weyl systems with low-order and higher order dispersion. The self-energy correction, symmetry, free energy, optical conductivity, density of states, and spectral function are studied. We found that, for Dirac/Weyl systems with higher order dispersion, the non-Fermi-liquid features remain even at finite chemical potential, and they are distinct from the ones in Fermi-liquid picture and the conventional non-Fermi-liquid picture. The Landau damping of the longitudinal excitations within random-phase-approximation (RPA) for the non-Fermi-liquid case are also discussed.

cond-mat.str-el↗

arXiv2019

Attractive polaron in a Dirac system within the ladder approximation

We investigate the properties of the attractive polaron formed by a single impurity dressed with the particle-hole excitations in a Dirac system at zero-temperature limit. Base on the single particle-hole variational ansatz, we deduce the expressions of the pair propagator, self-energy (negative), and the non-self-consistent medium $T$-matrix. Different to the self-consistent $T$-matrix which contains two channels due to the many-body effect, the non-self-consistent $T$-matrix discussed in this paper contains only the closed channel (i.e., the bare one) since we consider only a finite number of the majority particles. The chiral factor is also discussed within the pair propagator due to the scattering feature of the Dirac system (with a certain scattering angle $a$), and we found that the fluctuation of the pair propagator is proportional to the term ${\rm cos}\ a$. Finally, we also discuss the particle spectral function of the polaron in the presence of quantum many-body effect as well as the pair-propagator at finite temperature.

cond-mat.str-el↗

arXiv2018

Electronic properties of the parabolic Dirac system

We investigate the electronic properties of the parabolic Dirac system. In the pres- ence of magnetic field, we discuss the thermodynamical potential and the anomalous diamagnetism due to the presence of Dirac cone. The integer Hall conductivity and the intrinsic Hall conductivity induced by the Berry curvature are also investigated. Considering the disorder-induced self-energy in self-consistent Born approximation, the RKKY interaction, long-range scattering rate and the spectral function are also calculated, which are distinct to that of the clean system (without impurity).

cond-mat.mes-hall↗

arXiv2018

Dynamical current-current correlation in the two-dimensional parabolic Dirac system

We theoretically investigate the current-current correlation of the two-dimensional (2D) parabolic Dirac system in hexogonal lattice. The analytical expressions of the random phase approximation (RPA) susceptibility, Ruderman-Kittel-Kasuya-Yosida (RKKY) Hamiltonian, and the diamagnetic orbital susceptibility in noninteracting case base on the density-density or current-current correlation function are derived and quantitatively analyzed. In noninteracting case, the dynamical polarization with- in RPA and spin transverse susceptibility as well as the RKKY interaction (when close to the half-filling) are related to the the current-current response in the 2D parabolic Dirac system. Both the case of anisotropic dispersion and isotropic dispersion are discussed.

cond-mat.mes-hall↗

arXiv2018

Two-dimensional parabolic Dirac system in the presence of non-magnetic and magnetic impurities

We theoretically investigate the effect of the non-magnetic and magnetic impurities to the 2D parabolic Dirac system. The induced charge density by the charged impuri- ty is obtained by the linear response theory within the random phase approximation. We also detailly calculate the RKKY interaction between two magnetic impurities placed within the 2D sheet of the Dirac materials with isotropic and anisotropic dis- persion. For the anisotropic dispersion, the RKKY interaction is also anisotropic and related to the lattice parameters which can be obtained throuh the DFT calculation or the experiments. The fearures of the RKKY interaction also can be treated as a signature of the topological phase transition as well as the change of Berry curvature. Our results are also illuminating to the study of the static screening and the RKKY interaction of the isotropic or anisotropic 3D Dirac or Weyl systems.

cond-mat.mes-hall↗

arXiv2018

Electronic transport and dynamical polarization in bilayer silicene-like system

We investigate the semiclassical electronic transport properties of the bilayer silicene-like system in the presence of charged impurity. The trigonal warping due to the interlayer hopping, and its effect to the band structure of bilayer silicene is discussed. Besides the trigonal warping, the external field also gives rise to the anisotropic effect of the mobility (at finite temperature) which can be explored by the Boltzmann theory. The dynamical polarization as well as the scattering wave vector-dependent screening within random phase approximation are very important in determining the scattering behavior and the self-consistent transport. We detailly discuss the transport behavior under the short- or long-range potential. The phonon scattering with the acoustic phonon mode which dominant at high temperature is also studied within the density functional theory (DFT). Our results are also valid for the bilayer graphene or bilayer MoS$_{2}$, and other bilayer systems with strong interlayer coupling.

cond-mat.mes-hall↗

arXiv2018

Dynamical polarization, plasmon model, and the Friedel oscillation of the screened potential in doped Dirac and Weyl system

We discuss the dynamical polarization, plasmon dispersion, relaxation time, and the Friedel oscillation of screened potential of the two-dimension Dirac and three-dimension Weyl system (which are gapped) in the low-energy tigh-binding model. The results, like the Fermi wavevector, Thomas-Fermi wavevector, and longitudinal conductivity are obtained in different dimensions. Some important conclusions are detailedly discussed in this paper, including the screening character under short or long range Coulomb interaction, and the longitudinal conductivity in two- or three-dimensions. The longitudinal conductivity in optical limit is distinguishing for the case of two-dimension system and three-dimension system. The density-dependence (including the carrier density and the impurity concentration) of the Fermi wavevector, dc conductivity, and the relaxation time are discussed. Specially, for the doped Weyl system, the pumped carrier density due to the chiral anomaly origin from electromagnetic response is controlled by the internode relaxation time which has also been analyzed. %The model for which the calculations based on is the low-energy tight-binding model as presented in the Sec.2, %i.e., the results in this paper is for the low-temperature and low-energy case %and it's thus possible to carrying out a logarithmic self-energy correction to the relaxation time as we discussed in the text. %The difference between the longitudinal conductivity in serversal systems is also been discussed. Our results is helpful to the application of the Dirac or Weyl systems as well as the study on their low-temperature characters.

cond-mat.mes-hall↗

arXiv2018

Many-electron effect to the dynamical polarization of silicene-like two-dimension Dirac materials

We discuss the dynamical polarization with finite momentum and frequency in the presence of many-electron effect, including the screened Coulomb interaction, self-energy and vertex correction. The longitudinal conductivity, screened Coulomb interaction, and the response function are calculated. The behavior of the Dirac Fermions, including the propagation of the charge density which exhibits the causality, affects largely the low-temperature physical properties of the Dirac semimetal, like the silicene. For the polarization-related quantities (like the dielectric function), the method of standard random phase approximation (RPA) provides the non-interaction results (ignore the many electron effect), for a more exact result, we discuss the self-energy and the vertex correction for the two-dimension Dirac model. We found that, after the self-energy correction, the longitudinal conductivity increase compared to the noninteracting one in optical limit. For the renormalization treatment, the ultraviolet cutoff is setted as $Λ=t$ in our calculations, i.e., within the range between two Van Hove singularities where the density of states divergent logarithmically. %The $Λ$ is indeed a non-universal parameter and can also be choiced larger than arbitary ${\bf q}$ or $ω$. The (corrected) screened Coulomb interaction and the response function are also discussed. Our results are helpful to the application of the Dirac materials (or the Weyl semimetal) in spintronics or valleytronics.

cond-mat.mes-hall↗

arXiv2018

Dynamical polarization and the optical response of silicene and related materials

We discuss the dynamical polarization, optical response in low-frequency regime under in-plane polarized driving field of the silicene. The dynamical polarization, dielectric function, and absorption of radiation in infrared region are obtained and shown in the ${\bf q}\simω$ space, and they are distinguishing for the cases of chemical potential larger than the band gap and smaller than the band gap. The optical properties of silicene and the related group-V and group-VI materials: MoS$_{2}$ and black phosphorus are explored through the first-principle study. The plasmon which damped into the electron-hole pair in the single-particle excitation regime is also mentioned. The spin/valley polarized electron-hole pairs can be formed through that way, especially for the high-energy $π$-plasmon which begin to damp at the small ${\bf q}$-limit. The anisotropic effects induced by the warping structure or charged impurity, and the anisotropic polarization induced by the polarized incident light are also discussed. Our result exhibits the great potential in the optoelectronic applications of the materials we discussed.

cond-mat.mtrl-sci↗

arXiv2018

Electronic transport and the related anomalous effects in silicene-like hexagonal lattice

We investigate the anomalous effects due to the Berry correction and the considerable perturbations in the silicene-like hexagonal lattice system. The Berry curvature in periodic Bloch band system which related to the electromagnetic field is explored, the induced transverse anomalous velocity gives rise to the intrinsic Hall conductivity (without the vertex correction) expecially in the quantum anomalous Hall phase. The quantum anomalous Hall effect which related to the anomalous velocity term is detected, including the band avoided corssing effect and the generated special band gap. %{Enlarged Galilean symmetry of anyons and the Hall effect} The topological spin transport is affected by the Berry curvature %{Topological spin transport of a relativistic electron} %{Anomalous direction for skyrmion bubble motion} and the spin-current-induced Skyrmion spin texture motion is contrasted between the quantum spin Hall effect and quantum anomalous Hall effect. Since silicene involving the orbital degree of freedom, the orbital magnetic moment and orbital magnetization contributes significantly to the electronic transport properties of silicene %{Photoinduced quantum spin and valley Hall effects, and orbital magnetization in monolayer MoS2} as explored in this article. We also investigate the electronic tunneling properties of silicene in Josephon junction with the electric-field-induced Rashba-coupling, the anomalous effect due to the Berry phase is mentioned. Our results is meaningful to the application of the spintronics and valleytronics base on the silicene-like topological insulators.

cond-mat.mes-hall↗

arXiv2018

Josephson effect in silicene-based SNS Josephson junction: Andreev reflection and free energy

We investigate the Josephson effcet in superconductor-normal-superconductor junction (SNS) base on the doped unbiased silicene under the perpendicular electric field and off-resonance circularly polarized light. The Andreev reflection (including the retroreflection and specular one) during the subgap transport, the free energy, and the reversal of the Josephson effect as well as the emergence of $ϕ_{0}$-junction are exploited. The Andreev reflection is complete in the NS interface even for the clean interface and without the Fermi wave vector mismatch, which is opposite to the case of ferromagnet-superconductor interface. The important role played by the dynamical polarization of the degrees of freedom to the $0-π$ transition and the generation of $ϕ_{0}$-junction are mentioned in this paper. The scattering by the charged impurity in the substrate affects the transport properties in the bulk as well as the valley relaxation, which can be taken into consider by the macroscopic wave function. In short junction limit, the approximated results about the Andreev level and free energy are also discussed. Beside the low-energy limit of the tight-binding model, the finite-size effect need to be taken into account as long as the spacing model is much larger than the superconducting gap.

cond-mat.mes-hall↗

arXiv2018

Anomalous Rabi oscillation and related dynamical polarizations under the off-resonance circularly polarized light

We investigate the photoinduced effect to the silicene, which is a topological insulator, by the circularly polarized light in off-resonance regime with a frequency much larger than the critical value (also much larger than the frequency about the particle-hole pair creation), and with a perpendicular electric field. The anomalous Rabi frequency which is a non-linear optical, arised by the off-resonance circularly polarized light. The temporal behavior of the pseudospin, valley, and spin degrees of freedom, which are momentum- and quasienergy-dependent, are explored. The anomalous Rabi oscillation is also related to the photoinduced topological phase transition between the topological trivial state with zero Chern number and gapped edge state and the topological nontrivial state with nonzero Chern number and gapless edge state. The off-resonance laser can also induce the topological phase transition by manipulating the energy band structure, rather than excite the atoms to the high quantum-number states like the resonance light. The exchange between the radiation driving field and the two-component dynamical polarizations with the dipole oscillation, plays a important role in the determination of the out-of-plane spin polarization and the motion of the center of mass, which can induced a collapse-and-revival pattern under a certain condition. The Rabi oscillation observed in the motion of the center of mass in a laser-induced harmonic potential can be used to detect the time evolution of the atom polulation. Our results can also be applied to the other two-dimension low-energy Dirac models or the surface of the three-dimension topological insulators, and even the weyl semimetal with the photoinduced topological phase transition.

cond-mat.mes-hall↗

arXiv2018

Integer quantum Hall conductivity and longitudinal conductivity in silicene under the electric field and magnetic field

We investigate the integer Hall conductivity and longitudinal conductivity of silicene under the magnetic field, electric field, and exchange field in this letter. We focus not only on the low-temperature and $δ$-function impurities (i.e., independent of the scattering momentum) case, which only exist the intra-Landau level transition, but also on the case of inter-Landau level transition which also with the non-elastic scattering. The resulting longitudinal conductivity is very different with the intra-Landau level one at low-temperature. The exprssions of the Hall conductivity, longitudinal conductivity, valley contributed Hall conductivity, and the spin or valley Hall conductivity, are deduced in this letter. We also compute the dynamical polarization under the magnetic field which is a important quantity and has many exciting and novel properties, and with the screened scattering due to the charged impurities. The polarization function here is also related to the Landau level index under the magnetic field, and shows step-like feature rather than the logarithmically divergenas which appears for the zero-magnetic field case, and it's also naturally related to the conductivity in silicene. The generalized Laguerre polynomial is used in both the longitudinal conductivity and dynamical polarization function under magnetic field.

cond-mat.str-el↗

arXiv2018

Interband and intraband transition, dynamical polarization and screening of the monolayer and bilayer silicene in low-energy tight-binding model

We investigate the interband and intraband transition of the monolayer and AB-stacked bilayer silicene in low-energy tight-binding model under the electric field, where we focus on the dynamical polarization function, screening due to the charged impurity, and the plasmon dispersion. We obtain the logarithmically divergen polarization function within the random-phase-approximation (RPA) whose logarithmic singularities corresponds to the discontinuities of the first derivative which is at the momentum ${\bf q}=2{\bf k}_{F}$ in static case and indicate the topological phase transition point from the gapless semimetal to the gapped band insulator. We also obtain the power-law-dependent Friedel oscillation which can be enhanced by increasing the Rashba-coupling, that can contribute to the screened potential of the charged impurity which scale as $\sim r^{-1/2}$ in the short distance from the impurity and scale as $\sim r^{-1/3}$ in the long distance from the impurity. In the single-particle excitation regime with the electron-hole continuum, the interband and intraband transition happen, and the plasmon dispersion, which we mainly focus on the optical plasmon (which $\sim\sqrt{\bf q}$ in long-wavelength limit) in this paper, start to damped into the electron-hole pairs due to the nonzero imaginary part of the polarization function.

cond-mat.str-el↗

arXiv2018

Geometrical structure and the electron transport properties of monolayer and bilayer silicene near the semimetal-insulator transition point in tight-binding model

We investigate the electron properties of the monolayer and bilayer silicene which is the honeycomb lattice consist of silicon atoms, including the optical conductivity and charged impurity scattering, due to the quasipatricle Dirac-like behaviors near the K-point of silicene. The spin, valley, sublattice degrees of freedom are taken into consider in the multi-band tight-binding model. In momentum space, the scattering matrix which connects the two bare (without interaction) Green's functions in the quasiparticle momentum transport process, could be momentum-independent for the single impuirity configuration, which is similar to the case with small Coulomb coupling in the low-energy Dirac semimetallic system. While in the zero-frequency limit, or the frequency-independent case in the strong Coulomb coupling regime, the static polarization can be obtained by the random-phase-approximation, and it's important for the determination of the screened Coulomb scattering by the charge impurity. The antiferromagnetic order in the silicene is Hubbard-U-dependent, unlike the square lattice which with the antiferromagnetic ground state, and provides the premise of the phase transition from the nonmagnetic semimetal phase to the insulator one. We found that in the absence of electric field, the critical value of the phase transition from semimetal to insulator is 9 eV for the clear monolayer silicene, and is 12 eV for the 2nd AA-stacked bilayer silicene or the dirty monolayer silicene whcih with impurity strength 4 eV. While the behaviors of 1st AA-stacked bilayer silicene is found similar to the monolayer one. The in-plane optical conductivity also shows the same results.

cond-mat.str-el↗

arXiv2018

Tight-binding model and ab initio calculation of silicene with strong spin-orbit coupling in low-energy limit

We carry out both the tight-binding model and the $ab\ initio$ to study the layered silicene, the spin, valley, sublattice degrees of freedom are taken into consider and the effects of electric field, magnetic field, and even the light in finite frequency together with its interesting optical propertice, which are all closely related to the spin-orbit coupling and Rashba coupling and lead to the tunable phase transitions (between the nontrivial topological phase which has nonzero Chern number or nonzero spin Chern number and the trivial phase). An exotic quantum anomalous Hall insulator phase are found which has nonzero spin Chern number and nonzero valley Chern number and as a giant-application-potential spintronic and valleytronics in the two-ternimate devices based on the monolayer silicene for the information transmission. In fact, the gap-out action can be understanded by analyse the Dirac mass as well as the Zeeman splitting or the external-field-induced symmetry-broken, and the changes of gap has a general nonmonotone-variation characteristic under both the effects of electron filed-induced Rashba-coupling $R_{2}(E_{\perp})$ and the electron field-induced band gap, and the band inversion related to the spin-orbit coupling which absorbs both the spin and orbital angular of momentum may happen during this process. The quantized Hall/longitudinal conductivity together with the optical conductivity are also explored, we see that even in the quantum spin Hall phase without any magnetic field, the two-terminate conductivity can be reduced to the value $e^{2}/h$ by controlling the helical edge model, and it can be further reduced to $e^{2}/2h$ by applying the magnetic field which similar to the graphene.

cond-mat.mtrl-sci↗