Sn-doped Bi1.1Sb0.9Te2S, a bulk topological insulator with ideal properties

TL;DR

This paper introduces Sn-doped Bi1.1Sb0.9Te2S as an ideal bulk topological insulator with well-isolated surface states, high mobility, and reliable crystal growth, addressing longstanding challenges in the field.

Contribution

The study demonstrates that lightly Sn-doped Bi1.1Sb0.9Te2S can be reliably synthesized as high-quality bulk crystals with ideal topological insulator properties, overcoming previous material limitations.

Findings

Crystals exhibit well-isolated Dirac surface states

High surface state electronic mobility achieved

Reliable growth of large, high-quality bulk crystals

Abstract

A long-standing issue in topological insulator research has been to find a material that provides an ideal platform for characterizing topological surface states without interference from bulk electronic states and can reliably be fabricated as bulk crystals. This material would be a bulk insulator, have a surface state Dirac point energy well isolated from the bulk valence and conduction bands, have high surface state electronic mobility, and be growable as large, high quality bulk single crystals. Here we show that this major materials obstacle in the field is overcome by crystals of lightly Sn-doped Bi1.1Sb0.9Te2S (Sn-BSTS) grown by the Vertical Bridgeman method, which we characterize here via angle-resolved photoemission spectroscopy, scanning tunneling microscopy, transport studies of the bulk and surface states, and X-ray diffraction and Raman scattering. We present this new material as a bulk topological insulator that can be reliably grown and studied in many laboratories around the world.