Group delay time and Hartman effect in strained Weyl semimetals.

The group delay time was theoretically studied in Weyl semimetals (WSMs) in the presence of strain. The Hartman effect, where the delay time for tunneling through a barrier tends to a constant for large barrier thickness, can be observed in WSMs when the incident angles [Formula: see text] and [Formula: see text], and the unidirectional strain tensor u and shear strain tensor u , are larger than some critical values. We show that the Hartman effect is strongly dependent on the strength of the unidirectional strain tensor u and the ratio of the shear strain tensor [Formula: see text].

Electrically tunable valley polarization in Weyl semimetals with tilted energy dispersion.

Tunneling transport across electrical potential barriers in Weyl semimetals with tilted energy dispersion is investigated. We report that the electrons around different valleys experience opposite direction refractions at the barrier interface when the energy dispersion is tilted along one of the transverse directions. Chirality dependent refractions at the barrier interface polarize the Weyl fermions in angle-space according to their valley index.

Anomalous Photothermoelectric Transport Due to Anisotropic Energy Dispersion in WTe.

Band structures are vital in determining the electronic properties of materials. Recently, the two-dimensional (2D) semimetallic transition metal tellurides (WTe and MoTe) have sparked broad research interest because of their elliptical or open Fermi surface, making distinct from the conventional 2D materials. In this study, we demonstrate a centrosymmetric photothermoelectric voltage distribution in WTe nanoflakes, which has not been observed in common 2D materials such as graphene and MoS.

Quantum Dots Formed in Three-dimensional Dirac Semimetal CdAs Nanowires.

We demonstrate quantum dot (QD) formation in three-dimensional Dirac semimetal CdAs nanowires using two electrostatically tuned p-n junctions with a gate and magnetic fields. The linear conductance measured as a function of gate voltage under high magnetic fields is strongly suppressed at the Dirac point close to zero conductance, showing strong conductance oscillations. Remarkably, in this regime, the CdAs nanowire device exhibits Coulomb diamond features, indicating that a clean single QD forms in the Dirac semimetal nanowire.

Influence of Fermi arc states and double Weyl node on tunneling in a Dirac semimetal.

Most theoretical studies of tunneling in Dirac and the closely related Weyl semimetals have modeled these materials as single Weyl nodes described by the three-dimensional Dirac equation [Formula: see text]. The influence of scattering between the different valleys centered around different Weyl nodes, and the Fermi arc states which connect these nodes are hence not evident from these studies. In this work we study the tunneling in a thin film system of the Dirac semimetal NaBi consisting of a central segment with a gate potential, sandwiched between identical semi-infinite source and drain segments.

Klein tunneling in Weyl semimetals under the influence of magnetic field.

Klein tunneling refers to the absence of normal backscattering of electrons even under the case of high potential barriers. At the barrier interface, the perfect matching of electron and hole wavefunctions enables a unit transmission probability for normally incident electrons. It is theoretically and experimentally well understood in two-dimensional relativistic materials such as graphene.