Breaking of Phase Symmetry in Non-Equilibrium Aharonov-Bohm Oscillations through a Quantum Dot

TL;DR

This paper investigates how phase symmetry in Aharonov-Bohm oscillations with a quantum dot breaks beyond linear response, highlighting the role of inelastic cotunneling and level contributions in nonlinear regimes.

Contribution

It provides a theoretical explanation for phase symmetry breaking in AB oscillations with quantum dots, aligning with experimental observations.

Findings

Phase symmetry persists in nonlinear regime only after inelastic cotunneling onset.

Asymmetric AB oscillations occur when contributions from different levels cancel.

Theoretical results match experimental data on phase changes.

Abstract

Linear response conductance of a two terminal Aharonov-Bohm (AB) interferometer is an even function of magnetic field. This "phase symmetry" is no expected to hold beyond the linear response regime. In simple AB rings the phase of the oscillations changes smoothly (almost linearly) with voltage bias. However, in an interferometer with a quantum dot in its arm, tuned to the Coulomb blockade regime, experiments indicate that phase symmetry seems to persist even in the nonlinear regime. In this letter we discuss the processes that break AB phase symmetry. In particular we show that breaking of phase symmetry in such an interferometer is possible only after the onset of inelastic cotunneling, i.e. when the voltage bias is larger than the excitation energy in the dot. The asymmetric component of AB oscillations is significant only when the contributions of different levels to the symmetric component nearly cancel out (e.g., due to different parity of these levels), which explains the sharp changes of the AB phase. We show that our theoretical results are consistent with experimental findings.