QDev Seminar: Panagiotis Kotetes

Diagnosing Topological Phase Transitions in 1D Superconductors using Berry Singularity Markers

Panagiotis Kotetes

CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,

Chinese Academy of Sciences, Beijing 100190, China

In this talk, I propose to characterize topological phase transitions in 1D superconductors, e.g., single channel topological nanowires, using the approach of Berry singularity markers (BSMs) [1, 2]. The latter were recently introduced in a personal work [1], and define experimentally inferrable quantitites which can quantify how close is a system to a topological phase transition. Specifically, a BSM becomes nonzero only when the system is tuned in the vicinity of a Berry singularity and is equal to its charge. Experimentally identifying Berry singularities is of great significance, since these are responsible for the occurrence of topological phase transitions. To exemplify the BSM method, I discuss how this applies to the celebrated Kitaev chain model, as well as to a variant of it, which contains both nearest and next nearest neighbor equal spin pairings [2]. Depending on the situation, I identify pairs of external fields which can detect the topological charges of the Berry singularities which are responsible for the various topological phase transitions. These pairs of fields consist of either a flux knob which controls the supercurrent flow through the SC, or, strain, combined with a field which can tune the chemical potential of the system. Employing the present BSM approach appears to be within experimental reach for topological nanowire hybrids.

[1] P. Kotetes, arXiv:2111.12957 (2021).

[2] P. Kotetes, J. Phys.: Condens. Matter 34, 174003 (2022).