Coherent probing of excited quantum dot states in an interferometer

TL;DR

This paper investigates quantum dot states in an interferometer, revealing coherent elastic processes during inelastic cotunneling, with phase jumps indicating excited state involvement, using a novel measurement technique.

Contribution

It demonstrates the detection of coherent elastic processes via excited states in a quantum dot interferometer, advancing understanding of quantum coherence in inelastic regimes.

Findings

Coherent current contributions persist in nonlinear inelastic cotunneling.

Aharonov--Bohm oscillation phases show $$ jumps at inelastic process onsets.

Measurement technique reveals excited state occupation and relaxation rates.

Abstract

Measurements of elastic and inelastic cotunneling currents are presented on a two-terminal Aharonov--Bohm interferometer with a Coulomb blockaded quantum dot embedded in each arm. Coherent current contributions, even in magnetic field, are found in the nonlinear regime of inelastic cotunneling at finite bias voltage. The phase of the Aharonov--Bohm oscillations in the current exhibits phase jumps of $\pi$ at the onsets of inelastic processes. We suggest that additional coherent elastic processes occur via the excited state. Our measurement technique allows the detection of such processes on a background of other inelastic current contributions and contains information about the excited state occupation probability and the inelastic relaxation rates.