Tunability of the k-space Location of the Dirac Cones in the Topological Crystalline Insulator Pb1-xSnxTe

TL;DR

This study systematically investigates how the Dirac cones in the topological crystalline insulator Pb1-xSnxTe shift within the Brillouin zone during a topological phase transition, revealing their tunability and potential for material applications.

Contribution

It provides the first detailed experimental observation of the gradual movement and eventual disappearance of Dirac cones across the topological phase transition in Pb1-xSnxTe.

Findings

Dirac cones move toward the Xbar point as x decreases.

Dirac-cone surface states vanish for x <= 0.2.

Bulk band inversion occurs at the critical composition x_c ~ 0.25.

Abstract

We have performed systematic angle-resolved photoemission spectroscopy of the topological crystalline insulator (TCI) Pb1-xSnxTe to elucidate the evolution of its electronic states across the topological phase transition. As previously reported, the band structure of SnTe (x = 1.0) measured on the (001) surface possesses a pair of Dirac-cone surface states located symmetrically across the Xbar point in the (110) mirror plane. Upon approaching the topological phase transition into the trivial phase at x_c ~ 0.25, we discovered that Dirac cones gradually move toward the Xbar point with its spectral weight gradually reduced with decreasing x. In samples with x <= 0.2, the Dirac-cone surface state is completely gone, confirming the occurrence of the topological phase transition. Also, the evolution of the valence band feature is found to be consistent with the bulk band inversion taking place at x_c. The tunability of the location of the Dirac cones in the Brillouin zone would be useful for applications requiring Fermi-surface matching with other materials, such as spin injection.