Phonon Spectroscopy by Electric Measurements of Coupled Quantum Dots

TL;DR

This paper introduces a method for phonon spectroscopy using electric conductance measurements in a coupled quantum dot system, revealing how phonon emission affects quantum interference and enabling phonon density of states characterization.

Contribution

It proposes a novel electric measurement technique for phonon spectroscopy based on interference suppression in a T-shaped double quantum dot system.

Findings

Phonon emission from the second dot suppresses conductance interference.

The suppression pattern reflects the phonon density of states.

The method enables characterization of phonon coupling via electrical measurements.

Abstract

We propose phonon spectroscopy by electric measurements of the low-temperature conductance of coupled-quantum dots, specifically employing dephasing of the quantum electronic transport by the phonons. The setup we consider consists of a T-shaped double-quantum-dot (DQD) system in which only one of the dots (dot 1) is connected to external leads and the other (dot 2) is coupled solely to the first one. For noninteracting electrons, the differential conductance of such a system vanishes at a voltage located in-between the energies of the bonding and the anti-bonding states, due to destructive interference. When electron-phonon (e-ph) on the DQD is invoked, we find that, at low temperatures, phonon emission taking place on dot 1 does not affect the interference, while phonon emission from dot 2 suppresses it. The amount of this suppression, as a function of the bias voltage, follows the effective e-ph coupling reflecting the phonon density of states and can be used for phonon spectroscopy.