Semiconductor structures, low-dimensional systems, quantum phenomena

Shot noise in Aharonov–Bohm interferometer based on helical edge states

R. A. Niyazov^ab, I. V. Krainov^a, D. N. Aristov^abc, V. Yu. Kachorovskii<sup>a

a</sup> Ioffe Institute, 194021 St. Petersburg, Russia
^b The Petersburg Nuclear Physics Institute, The National Research Center "Kurchatov Institute", 188300 Gatchina, Russia
^c Saint Petersburg State University, 199034 St. Petersburg, Russia

Abstract: Shot noise in Aharonov–Bohm interferometers formed by helical edge states of two-dimensional topological insulators has been investigated. The study demonstrates that noise measurements provide unique opportunities for studying the breakdown of topological protection. Unlike conventional interferometers, where interference occurs in the ballistic regime, the manifestation of interference effects in helical systems requires the presence of defects leading to backscattering. A key finding is that the Fano factor exhibits oscillations with a magnetic flux period of $\Delta\phi$ = 1/2, where the oscillation amplitude is directly proportional to the backscattering strength. Furthermore, it is shown that simultaneous measurement of conductance and noise enables direct determination of the backscattering probability without detailed knowledge of contact properties. This provides a crucial experimental tool for identifying and quantifying the mechanisms responsible for the breakdown of topological protection in real materials. The results are particularly relevant for recent experiments with quantum point contacts on helical edge states and propose a noise spectroscopy method for characterizing topological phases. Our results are also compared with the case of a conventional spinless single-channel interferometer.

Received: 15.10.2025
Revised: 29.10.2025
Accepted: 06.11.2025

DOI: 10.61011/FTP.2025.08.62190.8665