Surface Landau levels and spin states in bismuth (111) ultrathin films.

Hongjian Du,Jinlong Yang,Jufeng Wang,Aidi Zhao,Xiaojun Wu,Mingyang Tian,Bing Wang,Yi Luo,Xia Sun,Xiaogang Liu,J G Hou

doi:10.1038/ncomms10814

Hongjian Du, Jinlong Yang + Show 9 more

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https://doi.org/10.1038/ncomms10814

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Abstract

The development of next-generation electronics is much dependent on the discovery of materials with exceptional surface-state spin and valley properties. Because of that, bismuth has attracted a renewed interest in recent years. However, despite extensive studies, the intrinsic electronic transport properties of Bi surfaces are largely undetermined due to the strong interference from the bulk. Here we report the unambiguous determination of the surface-state Landau levels in Bi (111) ultrathin films using scanning tunnelling microscopy under magnetic fields perpendicular to the surface. The Landau levels of the electron-like and the hole-like carriers are accurately characterized and well described by the band structure of the Bi (111) surface from density functional theory calculations. Some specific surface spin states with a large g-factor are identified. Our findings shed light on the exploiting surface-state properties of Bi for their applications in spintronics and valleytronics.

Highlights

The development of next-generation electronics is much dependent on the discovery of materials with exceptional surface-state spin and valley properties
Due to the rhombohedral symmetry in Bi crystal, the Bi (111) surface has a bilayer-terminated structure[19], forming a buckled honeycomb lattice that leads to valleys in surface-band structure, which is very similar to many other 2D valley materials with honeycomb lattice[1,2,3,4,5,6,7,13,14,15,16,17,18]
The surface-state bands near the Fermi level (EF) form electron pockets (EPs) around the G point and the M point, and the hole pockets (HPs) along the G-M directions in films thicker than 10 bilayers[39]. These multivalley states were characterized in Bi films and Bi crystal by angle-resolved photoemission spectroscopy (ARPES)[21,22,23,24,25,26,27]

Summary

Introduction

The development of next-generation electronics is much dependent on the discovery of materials with exceptional surface-state spin and valley properties. Due to the rhombohedral symmetry in Bi crystal, the Bi (111) surface has a bilayer-terminated structure[19], forming a buckled honeycomb lattice that leads to valleys in surface-band structure, which is very similar to many other 2D valley materials with honeycomb lattice[1,2,3,4,5,6,7,13,14,15,16,17,18] It has attracted increasingly study interest in Bi films or bilayers both theoretically[30,31,32] and experimentally[33,34,35,36], owing to the interesting one-dimensional topological edge state, that is, quantum spin Hall state[37,38]. It is observed that the out-of-plane spin states undergo spin polarization as the result of the Zeeman splitting, which may further cause the lift of the degeneracy of certain surface-state valleys

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