Robust Tunable Large-Gap Quantum Spin Hall States in Monolayer Cu₂S on Insulating Substrates

Abstract

Quantum spin Hall (QSH) insulators with large band gaps and dissipationless edge states are of both technological and scientific interest. Although numerous two-dimensional (2D) systems have been predicted to host the QSH phase, very few of them harbor large band gaps and retain their nontrivial band topology when they are deposited on substrates. Here, based on a first-principles analysis with hybrid functional calculations, we investigated the electronic and topological properties of inversion-asymmetric monolayer copper sulfide (Cu 2 S). Interestingly, we found that monolayer Cu 2 S possesses an intrinsic QSH phase, Rashba spin splitting, and a large band gap of 220 meV that is suitable for room-temperature applications. Most importantly, we constructed heterostructures of a Cu 2 S film on PtTe 2 , h-BN, and Cu(111) substrates and found that the topological properties remain preserved upon an interface with these substrates. Our findings suggest Cu 2 S as a possible platform to realize inversion-asymmetric QSH insulators with potential applications in low-dissipation electronic devices.

Effects of strain and thickness on the mechanical, electronic, and optical properties of Cu2Te

“…These materials have been synthesized in various stoichiometric ratios, including MX 2 (M: transition metal atoms; X: S, Se, and Te), [10][11][12][13][14] MX, [15][16][17][18][19] and M 2 X. 20,21 Among these, 2D transition-metal-rich TMCs (M 2 X) exhibit a diverse range of properties, such as tunable electronic band structures, 20 reversible thermal structural phase transitions, [21][22][23][24] excellent photocatalytic performance, 25,26 two-dimensional magnetic characteristics, 21,27 topological properties, 28 and a negative Poisson's ratio (auxetic materials). [29][30][31] These unique properties endow them with potential for the development of next-generation electronic and optoelectronic devices.…”

Nontrivial Topology in Monolayer MA2Z4 (M = Ti, Zr, or Hf; A = Si or Ge; and Z = N, P, As, Sb, or Bi)

“…Since graphene was obtained experimentally, thousands of new 2D materials have been proposed, − and many have been synthesized. − Beyond graphene, the other reported two-dimensional topological materials possessing honeycomb structures are III–V buckled honeycombs, , MXenes, − transition metal dichalcogenides (TMD), − Janus materials, , ternary transition metal chalcogenides, , functionalized Bi/Sb, arsenene oxide, and RuClBr . Additionally, other 2D topological compounds in different structures such as copper sulfide, Zintl compounds, , half-Heusler compounds, and ilmenite oxidizes also exist. While numerous studies have been conducted on the discovery of 2D topological materials based on honeycomb structures, the pursuit of materials exhibiting these unique properties is still in progress.…”

Large Gap Topological Insulating Phase and Anisotropic Rashba and Chiral Spin Textures in Monolayer Zintl A2MX2

“…Several comprehensive technical reviews on TIs − have been conducted. Moreover, numerous theoretical studies have demonstrated promising results, which include materials exhibiting honeycomb-like phases such as III–V buckled honeycombs, bismuthene, and graphene, , MXenes, − transition metal dichalcogenides (TMDs), organometallic frameworks, Janus materials, , ternary transition metal chalcogenides (TTMCs), , composite quantum compounds, and single-quintuple-layer Zintl compounds. , Furthermore, materials that exhibit nontrivial phases as a product of functionalization , or substrates effects − have also been theoretically predicted, − but are still in need of experimental investigation. Recently, a study in Zintl materials shows the tunability of topological states driven by alloying with highly magnetic atoms and a magnetic-field-driven changeover from a trivial insulator to a topological material with an applied magnetic field .…”