Topological Insulators

Abstract

Topological insulators are a new phase of matter that exhibits exotic surface electronic properties. Determining the spin texture of this class of material is of paramount importance for both fundamental understanding of its topological order and future spin-based applications. In this article, we review the recent experimental and theoretical studies on the differential coupling of leftversus right-circularly polarized light to the topological surface states in angle-resolved photoemission spectroscopy. These studies have shown that the polarization of light and the experimental geometry plays a very important role in both photocurrent intensity and spin polarization of photoelectrons emitted from the topological surface states. A general photoemission matrix element calculation with spin-orbit coupling can quantitatively explain the observations and is also applicable to topologically trivial systems. These experimental and theoretical investigations suggest that optical excitation with circularly polarized light is a promising route towards mapping the spin-orbit texture and manipulating the spin orientation in topological and other spin-orbit coupled materials.

Highly superlinear photogalvanic effects in (Bi$_{0.3}$Sb$_{0.7}$)$_2$(Te$_{0.1}$Se$_{0.9}$)$_3$: Probing 3D topological insulator surface states at room temperature

“…Topological insulators (TI) with low dimensional surface states described by the massless Dirac equation have recently moved into the focus of modern research. TIs challenge fundamental physical concepts as well as hold a great potential for applications [1][2][3][4][5]. Recently photocurrents excited by laser radiation in TI systems attracted growing attention because twithheir study opens up new opportunities for probing topological behavior of Dirac fermions (DF), for review see Ref.…”

Exotic rare earth-based materials for emerging spintronic technology

“…Carriers on topologically nontrivial surface states are massless fermions. Due to strong SOC, surface carriers show property of spin-momentum locking, meaning that the direction of spin is univocally determined by the direction towards which carriers are traveling[56]. Gapless topological surface (in 3D) and edge (in 2D) states are obtained through band inversion (Figure7) derived by relativistic spinorbit interactions, which naturally suppresses backscattering of carriers.…”

Dynamics of quantum gas in non-abelian gauge field

“…65 xx LIST OF FIGURES 3. 17 The magnetic field dependence of the 3 P 1 manifold: (a) the three hyperfine sub-spaces of F = 7/2, 9/2, and 11/2. (b) The magnetic field-dependence of the F = 9/2 manifold with respect to zero-field value up to the bias field 23.5 Gauss.…”

“…Soon after the theory paper of Bernevig and colleagues, quantum spin Hall effect was experimentally realized in a HgTe/(Hg,Cd)Te quantum well system [13]. After this experimental breakthrough, the field of topological matter has been at the forefront of the research in condensed matter [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31], photonics [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46], the cold atom community [47][48][49][50][51][52][53][54][55][56][57][58][59][60]…”

“…17) for i = {1, 2, 3}. The Heisenberg representation of the operators provides an algebraic convenience for the derivation of Zitterbewegung effect.…”