Engineering and Probing Topological Properties of Dirac Semimetal Films by Asymmetric Charge Transfer

Abstract

Dirac semimetals (DSMs) have topologically robust three-dimensional Dirac (doubled Weyl) nodes with Fermi-arc states. In heterostructures involving DSMs, charge transfer occurs at the interfaces, which can be used to probe and control their bulk and surface topological properties through surface-bulk connectivity. Here we demonstrate that despite a band gap in DSM films, asymmetric charge transfer at the surface enables one to accurately identify locations of the Dirac-node projections from gapless band crossings and to examine and engineer properties of the topological Fermi-arc surface states connecting the projections, by simulating adatom-adsorbed DSM films using a first-principles method with an effective model. The positions of the Dirac-node projections are insensitive to charge transfer amount or slab thickness except for extremely thin films. By varying the amount of charge transfer, unique spin textures near the projections and a separation between the Fermi-arc states change, which can be observed by gating without adatoms.

Magnetic Topological Semimetal Phase with Electronic Correlation Enhancement in SmSbTe

“…The color scale indicates the surface character, with 0 (light brown) referring to bulk state and 1 (dark brown) referring to surface states; see ref. [71]. c) Band structures of SmSbTe measured with a 30 eV photon energy along the and directions.…”

Two-dimensional Dirac fermions in thin films of Cd3As2

“…For example, theoretical predictions indicate that three-dimensional Dirac semimetals can be tuned into novel topological states if they are sufficiently thin to open up a band gap in their bulk electronic states. Depending on the boundary conditions, gapless, topologically protected Fermi arc states may exist on the surfaces even when the bulk is gapped [8][9][10][11][12][13] or the gapped material may transform into a quantum spin Hall (QSH) insulator with one-dimensional edge states [4,12,[14][15][16].…”

Observation of the Quantum Hall Effect in Confined Films of the Three-Dimensional Dirac Semimetal Cd3As2

“…The high carrier mobility and a clear quantized Hall achieved here are an important first step in the search for novel exotic states at high magnetic fields [39] and at interfaces [40] in this new class of topological semimetals. semimetal film with a bulk gap, according to theoretical predictions [19,33]. The surface arcs connect to projections of the Dirac nodes, leading to two copies of "Weyl orbits" and a connection through the bulk, indicated by the dashed lines [19,33].…”