QDev Seminar: Craig Polley

Researcher, ARPES project, MAX IV Laboratory, Lund University

Photoemission studies of topological crystalline insulator films and heterostructures

Commonly studied topological insulators such as bismuth selenide possess Dirac-like interface states 'protected' by time reversal symmetry. Topological crystalline insulators (TCIs) are a related system in which this protection instead arises from crystalline mirror symmetry. To date TCIs have only experimentally been realized in the family of IV-VI semiconductors (Pb,Sn)Se and (Pb,Sn)Te. Despite this apparently limited parameter space, these materials exhibit fascinating and diverse physical properties including valley-splitting, superconductivity and a temperature tunable topological phase transition.

In this talk I will review the in-house TCI research at the angle resolved photoemission beamlines in the MAXlab synchrotron laboratory in Sweden. We will see that it is straightforward to grow relatively high quality ternary IV-VI films in-situ, including the superconducting system (In,Sn)Te. We will also see that depositing thin layers of the normal semiconductor PbSe on the TCI (Pb,Sn)Se has a quite unusual effect on an electronic bandstructure that was already quite unusual to begin with.