Distinguishing the gapped and Weyl semimetal scenario in ZrTe5 : Insights from an effective two-band model

Abstract

Here we study the static and dynamic transport properties of a low-energy two-band model proposed previously in Martino et al. [PRL 122, 217402 (2019)], with an anisotropic in-plane linear momentum dependence and a parabolic out-of-plane dispersion. The model is extended to include a negative band gap, which leads to the emergence of a Weyl semimetal (WSM) state, as opposed to the gapped semimetal (GSM) state when the band gap is positive. We calculate and compare the zero-and finite-frequency transport properties of the GSM and WSM cases. The DC properties that are calculated for the GSM and WSM cases are Drude spectral weight, mobility, and resistivity. We determine their dependence on the Fermi energy and crystal direction. The in-and out-of-plane optical conductivities are calculated in the limit of the vanishing interband relaxation rate for both semimetals. The main common features are an ω 1/2 in-plane and ω 3/2 out-of-plane frequency dependence of the optical conductivity. We seek particular features related to the charge transport that could unambiguously point to one ground state over the other, based on the comparison with the experiment. Differences between the WSM and GSM are in principle possible only at extremely low carrier concentrations and at low temperatures.

Dynamical conductivity of lithium-intercalated hexagonal boron nitride films: A memory function approach

“…(4.1), this Fermi surface averaging is naturally present in the form of the Fermi-Dirac distribution derivative, which in the case of small T ε F restricts the summation over k to the Fermi surface. This condition fails in the low doped semiconductors [51], where a strong temperature dependence of the electron chemical potential completely smears the Fermi-Dirac distribution and its derivative. Since we know the phonon distributions, as well as the electron-phonon matrix elements, we proceed to evaluate Eq.…”

Optical conductivity and resistivity in a four-band model for ZrTe5 from ab initio calculations

“…Recently, a tentative minimal model for ZrTe 5 was put forward, based on optical conductivity measurements [24,33,34]. In contrast to a 3D Dirac semimetal model, it features a linear dispersion in two directions and parabolic dispersion in the orthogonal direction.…”

Gapped Dirac semimetal with mixed linear and parabolic dispersions

“…First, when M = 0 and (ζ , ζ z ) = (0, 0), H(k) reduces to the simplest Dirac semimetal model, which can describe the single DP phase in Na 3 Bi [29] and Cd 3 As 2 [30,31]. The second is the 2D conical model of ZrTe 5 [20][21][22], where only the linear term in the x − y plane and the parabolic term in the z−direction are included. So the model is equivalent to H(k) when ζ = v z = 0 and corresponds to the point of (ζ , ζ z ) = (0, ∞) in the phase diagram.…”

“…An optical spectroscopy study pointed out that the Dirac cone was only 2D and put forward a 2D conical model to describe its ground state [20]. The following theoretical studies revealed that the optical conductivities in the 2D conical model exhibit different dependence on the photon frequency along the x− and z−direction, as Re(σ x ) ∝ ω 1 2 and Re(σ z ) ∝ ω 3 2 [21,22].…”