Spin Berry phase in a helical edge state: S z nonconservation and transport signatures

• Published in: Physical review. B 2020-07, Vol.102 (3), Article 035423
• Main Authors: Adak, Vivekananda, Roychowdhury, Krishanu, Das, Sourin
• Format: Article
• Language: English
• ISSN: 2469-9950; 2469-9969; 2469-9969
• DOI: 10.1103/PhysRevB.102.035423

Topological protection of edge state in quantum spin Hall systems relies only on time-reversal symmetry. Hence, S-z conservation on the edge can be relaxed which can have an interferometric manifestation in terms of spin Berry phase. Primarily it could lead to the generation of spin Berry phase arising from a closed loop dynamics of electrons. Our work provides a minimal framework to generate and detect these effects by employing both spin-unpolarized and spin-polarized leads. We show that spin-polarized leads could lead to resonances or antiresonances in the two-terminal conductance of the interferometer. We further show that the positions of these antiresonances (as a function of energy of the incident electron) get shifted owing to the presence of spin Berry phase. Finally, we present simulations of a device setup using KWANT package which put our theoretical predictions on a firm footing.