Grzegorz Mazur (27.02, 10:15)
Affiliation: International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Poland Title: Experimental search for the origin of zero-energy modes in topological materials Abstract:Point-contact spectroscopy of several topological materials reveals a phase transition to a low temperature phase that is characterized by zero-energy modes superimposed on an energy gap showing a Bardeen-Cooper-Schrieffer-type of criticality. This behavior is not accompanied by a bulk superconductivity, which points to either local superconductivity or to the emergence of an unfamiliar ground state specific to topological matter. As found theoretically [Brzezicki et al., arXiv:1812.02168], one of these is a correlated many body state at surface atomic steps in topological crystalline insulators, whose domain walls, in an analogy to Su-Schrieffer-Heeger atomic chain systems, show low-energy excitations. We demonstrate, employing a soft point-contact method, that features characteristic for superconducting point contacts develop at the topological surfaces of diamagnetic, paramagnetic, and ferromagnetic Pb1−y−xSnyMnxTe. The temperature and field dependencies of the spectrum show BCS-type of critical behaviors that, however, is not accompanied by a global superconductivity. We examine possible sources of low-energy excitations and show that our data are consistent with Brzezicki's et al. theory.
UMO-2015/19/N/ST3/02626 and UMO-2017/27/B/ST3/02470.