Universal conductance fluctuations in nanoscale topological insulator devices

Abstract

Topological materials are promising candidates in fault-tolerant quantum information processing architectures, making it essential to understand the dephasing mechanisms in these materials. Here, we investigate gated, nanoscale mesas fabricated on thin films of cadmium arsenide (Cd3As2), a three-dimensional Dirac semimetal that can be tuned into different topological phases. We observe two independent types of conductance oscillations, one as a function of the applied magnetic field and the other as a function of the gate voltage. Varying the dimensions of the nanostructures allows the discrimination of a variety of scenarios for similar oscillations previously reported in the literature. We conclude that the conductance oscillations are not a signature of topological boundary states per se, but rather are universal conductance fluctuations. These results broadly inform future interpretations of electronic quantum interference in mesoscopic devices made from topological materials.

Influence of magnetic and electric fields on universal conductance fluctuations in thin films of the Dirac semi-metal Cd3As2

“…Dirac semimetals, a three-dimensional analog of graphene, are an important subset in this materials class, characterized by Dirac states in the bulk with degenerate Weyl nodes that are protected by the presence of both time-reversal symmetry (TRS) and inversion symmetry (IS) [3,5]. The response of Dirac semimetals to applied electrical and magnetic fields has been a matter of active discourse, in bulk crystals [6][7][8][9][10][11][12], thin films [13][14][15][16][17][18][19][20], and patterned micro/nanostructures [21][22][23][24]. An important question in this context is whether one can experimentally observe the expected transformation of a Dirac semimetal into a Weyl semimetal in a given material when the degeneracy of the Weyl nodes is removed by breaking TRS in an external magnetic field.…”

Influence of Magnetic and Electric Fields on Universal Conductance Fluctuations in Thin Films of the Dirac Semimetal Cd3As2

“…The past decade has seen enormous interest in the study of topological band structures created by the interplay between fundamental symmetries and strong spin–orbit coupling in a variety of quantum materials. − Dirac semimetals, a three-dimensional analogue of graphene, are an important subset in this materials class, characterized by Dirac states in the bulk with degenerate Weyl nodes that are protected by the presence of both time-reversal symmetry (TRS) and inversion symmetry (IS). , The response of Dirac semimetals to applied electrical and magnetic fields has been a matter of active discourse, in bulk crystals, − thin films, − and patterned micro-/nanostructures. − An important question in this context is whether one can experimentally observe the expected transformation of a Dirac semimetal into a Weyl semimetal in a given material when the degeneracy of the Weyl nodes is removed by breaking the TRS in an external magnetic field. Although angle-resolved photoemission spectroscopy (ARPES) could, in principle, be used to observe such a topological phase transition, it is technically impractical because of the need for a magnetic field.…”