Electric control of topological phase transitions in Dirac semimetal thin films

Abstract

Dirac semimetals host three-dimensional (3D) Dirac fermion states in the bulk of crystalline solids, which can be viewed as 3D analogs of graphene. Owing to their relativistic spectrum and unique topological character, these materials hold great promise for fundamental-physics exploration and practical applications. Particularly, they are expected to be ideal parent compounds for engineering various other topological states of matter. In this report, we investigate the possibility to induce and control the topological quantum spin Hall phase in a Dirac semimetal thin film by using a vertical electric field. We show that through the interplay between the quantum confinement effect and the field-induced coupling between sub-bands, the sub-band gap can be tuned and inverted. During this process, the system undergoes a topological phase transition between a trivial band insulator and a quantum spin Hall insulator. Consequently, one can switch the topological edge channels on and off by purely electrical means, making the system a promising platform for constructing topological field effect transistors.

Magnetooptical determination of a topological index

“…We believe that this approach can be applicable to any system supporting massive or massless Dirac fermions that go through a topological phase transition and that can be described by a BHZ Hamiltonian. 19,33,34,36,38,[63][64][65][66][67][68] . Accordingly, we propose to further study under the same scope compound series such as Hg 1-x …”

Molecular beam epitaxy of Cd3As2 on a III-V substrate

“…9,10 Cd 3 As 2 thin films are required for integration into devices and for the engineering of topological phases, using heterostructure approaches such as epitaxial strain, field effect, or quantum confinement. 11 Epitaxial films are also desirable to reduce extended defects. Previous studies of Cd 3 As 2 films have used amorphous substrates (e.g., SiO 2 , fused quartz, and borosilicate), [12][13][14] substrates with the rocksalt crystal structure (NaCl and KCl), 15,16 or weakly bonding substrates (mica).…”

Temperature-dependent n−p transition in a three-dimensional Dirac semimetal Na3Bi thin film

“…Na 3 Bi is a topological Dirac semimetal (TDS) with stable 3D Dirac points separated form the Γ point along the k z axis in its 1st Brillouin zone which has a linear band dispersion in all three momentum space directions [3,4]. The behavior of Dirac fermions in 3D opens up the possibility to study phenomena such as the chiral anomaly [5,6]; thin films geometry offers the opportunity to study ambipolar electronic devices [7], electron-hole pudding [8], along with the theoretical prediction of opening a band gap in excess of 300 meV in monolayer films [9] and a topological phase transition between trivial and non-trivial insulator that occurs at varying thickness or with applied electric field [10,11].…”