Abstract
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 {boldsymbol{H}}{boldsymbol{=}}{{boldsymbol{v}}}_{{boldsymbol{f}}}overrightarrow{{boldsymbol{p}}}cdot overrightarrow{{boldsymbol{sigma }}}. 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 Na3Bi consisting of a central segment with a gate potential, sandwiched between identical semi-infinite source and drain segments. The model Hamiltonian we use for Na3Bi gives, for each spin, two Weyl nodes separated in k-space symmetrically about kz = 0. The presence of a top and bottom surface in the thin film geometry results in the appearance of Fermi arc states and energy subbands. We show that (for each spin) the presence of two Weyl nodes and the Fermi arc states results in enhanced transmission oscillations, and finite transmission even when the energy falls within the bulk band gap in the central segment respectively. These features are not captured in single Weyl node models.
Highlights
The Dirac semimetal (DSM)[1,2,3,4] is a topologically non-trivial state which has attracted much attention recently
In order to elucidate the influence of multiple Weyl nodes and Fermi arc states on the transport compared with single Weyl node models of DSM/WSM tunneling, we study the tunneling in thin films of the DSM Na3Bi17–20 in an experimental setup similar to that in previous works, most of which have focused on Klein tunneling
We study the transmission from a semi-infinite source segment made of a DSM thin film to a semi-infinite drain segment of the same DSM thin film through a central segment which is subjected to a potential
Summary
In order to connect with earlier single Weyl node studies of tunneling in WSM/DSM materials, we consider the energy and gate potential ranges when there is only to single propagating bulk band per valley and/or the Fermi arc state in the source and drain leads, and the central segment, and consider transmission from only the +ve kz valley bulk states. Between 58 meV < E2 < 63 meV the ky range spanned by the elliptical cross sections of the central segment Dirac hole cones shrink with increasing E2 to 0 at the bottom of the bulk energy gap This leads to the narrowing of the range of φ with relatively high transmission to zero.
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