@article{52d529e696b647e3aa524f653692d935,
title = "Unconventional transformation of spin Dirac phase across a topological quantum phase transition",
abstract = "The topology of a topological material can be encoded in its surface states. These surface states can only be removed by a bulk topological quantum phase transition into a trivial phase. Here we use photoemission spectroscopy to image the formation of protected surface states in a topological insulator as we chemically tune the system through a topological transition. Surprisingly, we discover an exotic spin-momentum locked, gapped surface state in the trivial phase that shares many important properties with the actual topological surface state in anticipation of the change of topology. Using a spin-resolved measurement, we show that apart from a surface bandgap these states develop spin textures similar to the topological surface states well before the transition. Our results offer a general paradigm for understanding how surface states in topological phases arise from a quantum phase transition and are suggestive for the future realization of Weyl arcs, condensed matter supersymmetry and other fascinating phenomena in the vicinity of a quantum criticality.",
author = "Xu, {Su Yang} and Madhab Neupane and Ilya Belopolski and Chang Liu and Nasser Alidoust and Guang Bian and Shuang Jia and Gabriel Landolt and Batosz Slomski and Dil, {J. Hugo} and Shibayev, {Pavel P.} and Susmita Basak and Chang, {Tay Rong} and Jeng, {Horng Tay} and Cava, {Robert J.} and Hsin Lin and Arun Bansil and Hasan, {M. Zahid}",
note = "Funding Information: Work at Princeton University is supported by DOE/BES DE-FG-02-05ER46200. M.Z.H. acknowledges the visiting scientist{\textquoteright}s support from Lawrence Berkeley National Laboratory and additional support from the A.P. Sloan Foundation. The SR photoemission measurements using synchrotron X-ray facilities were supported by the Swiss Light Source, the Swiss National Science Foundation (PP00P21447421). Crystal growth was supported by NSF-DMR-0819860. S.J. was supported by the National Basic Research Program of China (Grant nos. 2013CB921901 and 2014CB239302).Theoretical computations were supported by the US Department of Energy (DE-FG02-07ER46352 and AC03-76SF00098) as well as the National Science Council and Academia Sinica in Taiwan, and benefited from the allocation of supercomputer time at NERSC and the Northeastern University{\textquoteright}s Advanced Scientific Computation Center. H.L. acknowledges the Singapore National Research Foundation for the support under NRF Award no. NRF-NRFF2013-03. T.-R.C. and H.-T.J. were supported by the National Science Council, Taiwan. We thank Sung-Kwan Mo, Alexei Fedorov, Jonathan Denlinger and Makoto Hashimoto for beamline assistance at the Lawrence Berkeley National Laboratory and the SSRL. We also gratefully acknowledge Nan Yao and Gerald R. Poirier for the assistance of the EDS measurements at the Imaging and Analysis Center (IAC) at the Princeton University. The work also benefited from the helpful discussions with Chen Fang and B. Andrei Bernevig. Publisher Copyright: {\textcopyright} 2015 Macmillan Publishers Limited. All rights reserved.",
year = "2015",
month = apr,
day = "17",
doi = "10.1038/ncomms7870",
language = "English (US)",
volume = "6",
journal = "Nature Communications",
issn = "2041-1723",
publisher = "Nature Publishing Group",
}