Internal chiral spin structure of topological-insulator/metal superlattices

¹ College of Science, Nanjing University of Science and Technology - Nanjing 210094, China
² Department of Physics, University of Illinois at Urbana-Champaign - 1110 West Green Street, Urbana, IL 61801-3080, USA
³ Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign 104 South Goodwin Avenue, Urbana, IL 61801-2902, USA
⁴ Synchrotron Radiation Center, University of Wisconsin-Madison - 3731 Schneider Drive, Stoughton, WI 53589-3097, USA

^(a) phywangxx@njust.edu.cn
^(b) tcchiang@illinois.edu

Received: 30 October 2013
Accepted: 21 April 2014

Abstract

The electronic structure of a superlattice, made of a topological insulator (Bi₂Se₃) and a normal metal (Ca/Sr alloy), has been studied by first-principle calculations. Even though spatial inversion and time-reversal symmetries require all electronic states in the system be spin degenerate spin separation in real space is permitted. The system forms a nontrivial three-dimensional spin structure by self-organization into a dense periodic stack of spin-carrying electron sheets of alternating chirality imbedded in the subsurface regions of the topological insulator layers. This highly anisotropic spin configuration makes the system a promising candidate for field-effect spin transducers and transistors.