Orbital Pseudospin-Momentum Locking in Two-Dimensional Chiral Borophene

Abstract

Recently, orbital-textures have been found in Rashba and topological insulator (TI) surface states as a result of the spin-orbit coupling (SOC). Here, we predict a px/py orbital texture, in linear dispersive Dirac bands, arising at the K/K' points of χ-h0 borophene chiral monolayer. Combining first-principles calculations with effective hamiltonians, we show that the orbital pseudospin has its direction locked with the momentum in a similar way as TIs' spin-textures. Additionally, considering a layer pseudospin degree of freedom, this lattice allows stackings of layers with equivalent or opposite chiralities. In turn, we show a control of the orbital textures and layer localization through the designed stacking and external electric field. For instance, for the opposite chirality stacking, the electric field allows for an on/off switch of the orbital-textured Dirac cone.

Disentangling Orbital and Valley Hall Effects in Bilayers of Transition Metal Dichalcogenides

“…Introduction.-The orbital Hall effect (OHE) is the orbital analog of the spin Hall effect and consists in the appearance of a transverse current of orbital angular momentum that is induced by a longitudinally applied electric field [1]. Recently, a renewed interest in orbital magnetism and other orbital effects [2][3][4][5] gave origin to various theoretical studies on the OHE and related phenomena [6][7][8][9][10][11][12][13][14][15]. The possibility of using the OHE to generate orbital torque in magnetic materials [16,17] motivated new experimental works on orbital dynamics in magnetic multilayers [18,19], raising expectations that orbital angular degrees of freedom may eventually be employed to process information in logic and memory devices.…”

“…The interrelation between the OHE and the presence of orbital textures in reciprocal space [10] has been established and characterized both theoretically and experimentally in several low-dimensional materials [5,6,12,13,20,21], widening the class of systems that may be utilized for orbitronic applications. More specifically, the occurrence of a relatively large OHE has been predicted in the 2H structural phase of transition metal dichalcogenide (TMD) monolayers [6,7], where it is associated with the presence of a Dresselhaus-like orbital texture around the valleys [6].…”

Advances in photonics of recently developed Xenes

“…In Rashba or topological insulator systems, the orbital textures associated with spin arising from strong spin-orbit coupling (SOC) are found to be significant in switching the magnetic moment of ferromagnets. Intriguingly, orbital texture without SOC is recently observed in the borophene χ-h 0 lattice with two mirror-symmetric chirality (C1 and C2; Figure 4A) [79]. It is mainly attributed to the presence of linear dispersive Dirac cone that gives rise to an orbital pseudospin with momentum locking and opposed textures at K and K′ valleys ( Figure 4A).…”

“…Right: 3D band structure for the same chirality stacking (C1-C1) and opposite chirality stacking (C1-C2) under electric field. Reproduced with permission[79]. Copyright 2019, American Chemical Society.…”

Engineering Metal-spxy Dirac Bands on the Oxidized SiC Surface

“…3(a)-3(d). It is worth noting that other 2D lattices can be designed on the (M)Si 2 O 5 /SiC surface, for instance, the ones predicted/synthesized based on boron atoms [48][49][50].…”