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arXiv · 1204.5812

Spin Polarization of Gapped Dirac Surface States Near the Topological Phase Transition in TlBi(S1-xSex)2

S. Souma·M. Komatsu·M. Nomura·T. Sato·A. Takayama·T. Takahashi·K. Eto·Kouji Segawa·Yoichi Ando
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Abstract

We performed systematic spin- and angle-resolved photoemission spectroscopy of TlBi(S1-xSex)2 which undergoes a topological phase transition at x ~ 0.5. In TlBiSe2 (x = 1.0), we revealed a helical spin texture of Dirac-cone surface states with an intrinsic in-plane spin polarization of ~ 0.8. The spin polarization still survives in the gapped surface states at x > 0.5, although it gradually weakens upon approaching x = 0.5 and vanishes in the non-topological phase. No evidence for the out-of-plane spin polarization was found irrespective of x and momentum. The present results unambiguously indicate the topological origin of the gapped Dirac surface states, and also impose a constraint on models to explain the origin of mass acquisition of Dirac fermions.

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S. Souma, M. Komatsu, M. Nomura, T. Sato, A. Takayama, T. Takahashi, K. Eto, Kouji Segawa, Yoichi Ando. 2012-08-21. Spin Polarization of Gapped Dirac Surface States Near the Topological Phase Transition in TlBi(S1-xSex)2. https://doi.org/10.1103/physrevlett.109.186804

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