Magnetothermoelectric transport properties in phosphorene

Abstract

We numerically study the electrical and thermoelectric transport properties in phosphorene in the presence of both a magnetic field and disorder. The quantized Hall conductivity is similar to that of a conventional two-dimensional electron gas, but the positions of all the Hall plateaus shift to the left due to the spectral asymmetry, in agreement with the experimental observations. The thermoelectric conductivity and Nernst signal exhibit remarkable anisotropy, and the thermopower is nearly isotropic. When a bias voltage is applied between top and bottom layers of phosphorene, both thermopower and Nernst signal are enhanced and their peak values become large. * Electronic address:

Hole mobility of strained GaN from first principles

“…In this latter case we rely on the crystal symmetry operations on the kpoint grid to reduced the number of electron-phonon matrix elements to be explicitly computed. We emphasize that, while in some systems the SERTA is accurate enough for predictive calculations of carrier mobilities 82,85 , this is not true in general 86 . In the present case of wurtzite GaN, we find that the self-consistent solution of the BTE yields enhancement factors of about 2 of the electron and hole mobility upon the values obtained within the SERTA, as shown on Fig.…”

“…The carrier drift mobility µ describes the change of steady-state carrier current J α = e(n e µ e,αβ +n h µ h,αβ )E β due to an applied external electric field E, where Greek indices denote Cartesian coordinates, n e and n h the electron and hole density, respectively. The mobility can be computed using the linearized Boltzmann transport equation (BTE) [79][80][81][82][83][84][85][86][87] , which for electrons reads:…”

First-principles calculations of charge carrier mobility and conductivity in bulk semiconductors and two-dimensional materials

“…We also note that at very low temperature, the mobility is no longer limited by phonon-induced scattering and other mechanisms need to be taken into account [69]. Finally, the importance of including spinorbit coupling (SOC) was recently highlighted even for materials like silicon, where the spin-orbit splitting is small [109,55].…”

“…In this case, converged calculations required grids as dense as 400×400×400 k-points and the iterative BTE solution yielded mobility values approximately 50% higher than in the SERTA [109]. Moreover, significantly denser grids are needed to obtain converged mobility results at lower temperatures and this may explain why many authors present calculation results at relatively high temperatures.…”

“…Indeed, within this approximation, the scattering rate is directly related to the imaginary part of the retarded electronphonon (Fan-Migdal) self-energy and can therefore be computed easily. However, this approximation is not reliable in materials with strong band structure anisotropy and in polar materials [108,109]. In order to go beyond SERTA, it is possible to solve the BTE iteratively, with a small computational overhead.…”