Effect of dilute magnetism in a topological insulator*

Three-dimensional topological insulator (TI) has emerged as a unique state of quantum matter and

generated enormous interests in condensed matter physics. The surfaces of a three-dimensional TI

consist of a massless Dirac cone, which is characterized by the Z₂ topological invariant. Introduction

of magnetism on the surface of a TI is essential to realize the quantum anomalous Hall effect and

other novel magneto-electric phenomena. Here, by using a combination of first-principles calculations,

magneto-transport and angle-resolved photoemission spectroscopy (ARPES), we study the 

electronic properties of gadolinium (Gd)-doped Sb₂Te₃. Our study shows that Gd doped Sb₂Te₃ is

a spin-orbit-induced bulk band-gap material, whose surface is characterized by a single topological

surface state. This surface state, above the Fermi level is further confirmed by time-resolved ARPES (tr-ARPES)

measurements. Our results provide a new platform to investigate the interactions between dilute

magnetism and topology in magnetic doped topological materials.