title: Observation of a topological crystalline insulator phase and topological phase transition in Pb(1-x)Sn(x)Te.
abstract: A topological insulator protected by time-reversal symmetry is realized via spin-orbit interaction-driven band inversion. The topological phase in the Bi(1-x)Sb(x) system is due to an odd number of band inversions. A related spin-orbit system, the Pb(1-x)Sn(x)Te, has long been known to contain an even number of inversions based on band theory. Here we experimentally investigate the possibility of a mirror symmetry-protected topological crystalline insulator phase in the Pb(1-x)Sn(x)Te class of materials that has been theoretically predicted to exist in its end compound SnTe. Our experimental results show that at a finite Pb composition above the topological inversion phase transition, the surface exhibits even number of spin-polarized Dirac cone states revealing mirror-protected topological order distinct from that observed in Bi(1-x)Sb(x). Our observation of the spin-polarized Dirac surface states in the inverted Pb(1-x)Sn(x)Te and their absence in the non-inverted compounds related via a topological phase transition provide the experimental groundwork for opening the research on novel topological order in quantum devices.
authors.affiliation: Joseph Henry Laboratory, Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Su-Yang
authors.initials: SY
authors.lastname: Xu
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
authors.forename: N
authors.initials: N
authors.lastname: Alidoust
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authors.lastname: Neupane
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authors.lastname: Qian
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authors.lastname: Belopolski
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authors.lastname: Denlinger
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authors.initials: YJ
authors.lastname: Wang
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authors.lastname: Lin
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authors.lastname: Wray
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authors.lastname: Landolt
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authors.lastname: Slomski
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authors.lastname: Marcinkova
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authors.lastname: Gibson
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authors.lastname: Sankar
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authors.initials: RJ
authors.lastname: Cava
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authors.lastname: Bansil
authors.forename: M Z
authors.initials: MZ
authors.lastname: Hasan