Atomically uniform Sb(111) films are fabricated by the method of molecular beam epitaxy on an optimized Si(111) surface. Two dimensional quantum well states and topological surface states in these films are well resolved as measured by angle-resolved photoemission spectroscopy. We observe an evolution of direct transition resonances by varying the excitation photon energy (and thus the perpendicular crystal momentum). The experimental results are reproduced in a comprehensive model calculation taking into account first-principles calculated initial states and time-reversed low-energy-electron-diffraction final states in the photoexcitation process. The resonant behavior illustrates that the topological surface states and the quantum well states are analytically connected in momentum space in all three dimensions.
@article{arxiv.1511.02419,
title = {Direct Transition Resonance in Atomically Uniform Topological Sb(111) Thin Films},
author = {Guang Bian and Caizhi Xu and Tay-Rong Chang and Xiaoxiong Wang and Saavanth Velury and Jie Ren and Hao Zheng and Horng-Tay Jeng and T. Miller and M. Zahid Hasan and T. -C. Chiang},
journal= {arXiv preprint arXiv:1511.02419},
year = {2015}
}