A stable three-dimensional topological Dirac semimetal Cd3As2

Abstract

Three-dimensional (3D) topological Dirac semimetals (TDSs) are a recently proposed state of quantum matter that have attracted increasing attention in physics and materials science. A 3D TDS is not only a bulk analogue of graphene; it also exhibits non-trivial topology in its electronic structure that shares similarities with topological insulators. Moreover, a TDS can potentially be driven into other exotic phases (such as Weyl semimetals, axion insulators and topological superconductors), making it a unique parent compound for the study of these states and the phase transitions between them. Here, by performing angle-resolved photoemission spectroscopy, we directly observe a pair of 3D Dirac fermions in Cd3As2, proving that it is a model 3D TDS. Compared with other 3D TDSs, for example, β-cristobalite BiO2 (ref. 3) and Na3Bi (refs 4, 5), Cd3As2 is stable and has much higher Fermi velocities. Furthermore, by in situ doping we have been able to tune its Fermi energy, making it a flexible platform for exploring exotic physical phenomena.

Nernst and magnetothermal conductivity in a lattice model of Weyl fermions

“…Another route which can result in the experimental verification of the novel WSM phase is to first realize a 3D Dirac semimetal and then break time reversal symmetry by applying a magnetic field, which will split a Dirac cone into a pair of Weyl nodes. Na 3 Bi and Cd 3 As 2 were recently proposed to be Dirac semimetals 27,28 , and also have been confirmed experimentally by a series of experiments [29][30][31][32][33][34][35][36][37] . In Bi 1−x Sb x for x ∼ 3 − 4% also the Dirac semimetal phase has been predicted [38][39][40] , and experimental signatures of realizing a WSM phase by breaking TR have been reported 41 .…”

“…Cd 3 As 2 , and Bi 1−x Sb x with x ∼ 3 − 4% were recently proposed 27,28,[38][39][40] , and also realized experimentally to be Dirac semimetals [29][30][31][32][33][34][35][36][37]41 . This has paved the way to realizing a TR broken WSM phase, which has been so far verified by a few experimental signatures 24,37,41,42 .…”

Optical spectroscopy study of the three-dimensional Dirac semimetalZrTe5

“…Among them, Na 3 Bi and Cd 3 As 2 are the two best known compounds 16,17 . They were confirmed to be 3D Dirac semimetals by angle-resolved photoemission spectroscopy (ARPES) experiments [18][19][20][21] . Very recently, another layered compound, ZrTe 5 , was suggested to be also a 3D Dirac semimetal based on transport and ARPES experiments 13 .…”

Unconventional superconductivity at mesoscopic point contacts on the 3D Dirac semimetal Cd3As2

“…Although the 3D topological Dirac semi-metals [1][2][3] can be stable where the Dirac points are protected by symmetry, they exist close to topological phase boundaries, and therefore, they are expected to be driven into topologically distinct phases by explicit symmetry breaking [4]. The proposed new phases of matter that could be derived from a 3D topological Dirac semi-metal through explicit symmetry breaking include new topological insulators [5], Weyl semi-metals [6,7], and topological superconductors [8][9][10][11].…”