Unconventional transformation of spin Dirac phase across a topological quantum phase transition

• Published in: Nature communications 2015-04, Vol.6 (1), p.6870-6870, Article 6870
• Main Authors: Xu, Su-Yang, Neupane, Madhab, Belopolski, Ilya, Liu, Chang, Alidoust, Nasser, Bian, Guang, Jia, Shuang, Landolt, Gabriel, Slomski, Batosz, Dil, J. Hugo, Shibayev, Pavel P., Basak, Susmita, Chang, Tay-Rong, Jeng, Horng-Tay, Cava, Robert J., Lin, Hsin, Bansil, Arun, Hasan, M. Zahid
• Format: Article
• Language: English
• Subjects: 140/146; 639/301/119/2792; 639/301/119/2795; 639/766/119/1001; 639/766/25; applied physics; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; condensed matter; Humanities and Social Sciences; multidisciplinary; physical sciences; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms7870

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. In topological insulators, topology imposes a quantum phase transition between the trivial and nontrivial phases. Here, Xu et al. demonstrate how properties of the topological surface states emerge in the trivial phase of BiTl(S 1-δ Se δ ) 2 when close to its chemically tuned phase transition.