WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Phys Rev Lett. 2012 Nov 2;109(18):186804. doi: 10.1103/PhysRevLett.109.186804.
We performed systematic spin- and angle-resolved photoemission spectroscopy of TlBi(S(1-x)Se(x))(2) which undergoes a topological phase transition at x ~ 0.5. In TlBiSe(2) (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 nontopological 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.
我们对 TlBi(S(1-x)Se(x))(2) 进行了系统的自旋和角度分辨光发射谱研究，该材料在 x ~ 0.5 处经历拓扑相变。在 TlBiSe(2)（x = 1.0）中，我们揭示了具有约 0.8 的本征面内自旋极化的狄拉克锥表面态的螺旋自旋织构。在 x > 0.5 的能隙表面态中，自旋极化仍然存在，尽管它在接近 x = 0.5 时逐渐减弱，并在非拓扑相中消失。无论 x 和动量如何，都没有发现面外自旋极化的证据。目前的结果明确表明了能隙狄拉克表面态的拓扑起源，也对解释狄拉克费米子质量获取的模型提出了限制。
