Spectro-microscopic Studies at Polar Surfaces of Layered Rashba Semiconductors.
Christopher John Butler1*, Po-Ya Yang1, Shih-Hao Hsu1, Chun-I Lu2, Hung-Wei Shiu2, Lo-Yueh Chang2, Jhen-Yung Hong1, Kui-Hon Ou Yang1, Raman Sankar3,4, Chia-Hao Chen2, Chao-Cheng Kaun5,6, Ching-Ming Wei3, Fang-Cheng Chou2,4,7, Minn-Tsong Lin1,3
1Department of Physics, National Taiwan University, Taipei, Taiwan
2National Synchrotron Radiation Research Center, Hsinchu, Taiwan
3Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
4Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
5Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
6Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
7Taiwan Consortium of Emergent Crystalline Materials, National Science Council, Taipei, Taiwan
* presenting author:Christopher Butler, email:yangyuchris@gmail.com
The Rashba semiconductors BiTeX (X = Cl, Br, I) possess some functional properties reminiscent of the well-known topological insulators: A bulk band-gap and high mobility, two dimensional and spin-helical surface carriers.[1] Due to their polar structure, they also feature strong surface band bending which shifts either the conduction or valence band to the Fermi level, depending on the polarity of the chosen surface termination. Thus they offer a choice of two-dimensional spin-helical carriers with either electron-like or hole-like dispersion, providing a versatile platform for all-electric control of spin currents in novel spintronic device designs, among other more exotic applications.[2] In this work we perform scanning tunneling microscopy investigations on two Rashba semiconductors. Using tunneling spectroscopy measurements, we observe the surface polarization induced band bending at the tellurium and halide terminations, and investigate the growth method and composition dependent control of domains of opposite stacking order.[3,4] We discuss in detail the possible influences of these and other types of defect on in-plane conductance.
This project is financially sponsored by Ministry of Science and Technology (MOST 104-2119-M-002-029& MOST 103-2120-M-002 -001 & MOST 101-2112-M-002-024-MY3)

1. K. Ishizaka et al., Nat. Mater. 10, 521-526 (2011).
2. J. D. Sau et al., Phys. Rev. Lett. 104, 040502 (2010).
3. C. J. Butler, et al., Nat. Commun. 5, 4066 (2014).
4. R. Sankar, et al., CrystEngComm 16, 8678-8683 (2014).

Keywords: Rashba effect, polar surfaces, scanning tunneling microscopy, scanning tunneling spectroscopy