Phonon-limited mobility of Dirac fermions in three-dimensional Dirac semimetal Cd3As2

Abstract

A theoretical model is presented for the phonon limited mobility of the Dirac-Fermion gas in a three-dimensional (3D) Dirac semimetal Cd 3 As 2 considering scattering from both the acoustic and the optical phonons. Screening effects are taken into account and it is found that they lead to a significant enhancement of the mobility. Simple analytical equations and power laws are obtained in both the Bloch-Gruneisen and equipartition regimes. The dependence of mobility on the temperature T and the electron density n e is investigated. It is found that optical phonon limited mobility µ op dominates over the acoustic phonon limited mobility µ ap in the higher temperature region. There is a crossover of µ ap and µ op and the crossover temperature T c shifts to higher value with increasing n e . Our calculations of the mobility are in good agreement with the recent experimental data. Comparison is also made with the results in the conventional 3D electron gas in a degenerate semiconductor. *

Drift velocity saturation and large current density in intrinsic three-dimensional Dirac semimetal cadmium arsenide

“…(4a) -(4d) reduce to those in Ref. [22]. We also find that ne dependence of hot electron μap-BG is given by…”

“…This has been achieved by introducing isotropic disorder in the sample. We point out that, while disorder scattering determines the low field mobility at low temperature [21,22], the saturation of vd has been attributed to the scattering by optical phonons. Consequently, the saturation of velocity and hence the current density are not affected by doping, In graphene, it has been shown that larger the acoustic deformation potential coupling constant D, larger is the vd and vds [32].…”

“…This is because, scattering by acoustic phonons is dominant up to ~ 200 K as the optical phonon scattering becomes important above this temperature due to the large optical phonon energy (~ 190 meV). In Dirac semimetal Cd3As2 a variation of D may affect vds to a small extent as the optical phonon scattering becomes dominant for temperatures > ~ 40-50 K [22] and the saturation of drift velocity occurs at relatively higher temperature.…”

“…The electron energy dispersion is linear, i.e., Ek = ћvFk, and the density of states is D(Ek) = gEk 2 /[2π 2 (ћvF) 3 ], where vF is the Fermi velocity, k is the 3D wave vector, and g = gsgv, with gs (gv) denoting the spin (valley) degeneracy of the electron. We assume, that the electronic dispersion is isotropic [4,[21][22][23] although it has been found by some authors to be anisotropic [3,7,8]. In an applied electric field E electrons gain energy and momentum, and in the steady state they establish their electron temperature Te (> T, the lattice temperature) and drift velocity vd, by losing extra energy and momentum to the lattice (phonons).…”

“…From the Boltzmann transport equation technique, using the relaxation time approximation, an expression for the mobility is given by [22] μi = σi /nee, with electrical conductivity σi = e 2 Koi , (1) where,…”