Remote entropy measurement in coupled quantum dots

TL;DR

This paper demonstrates that Maxwell relation-based measurements in coupled quantum dots can probe the entropy change of the entire system, including the surrounding environment, beyond just the added electron.

Contribution

It introduces a method to measure the entropy change of an entire coupled quantum dot system using charge measurements, extending previous techniques.

Findings

Charge measurements reveal entropy changes of the two-dot system.

Method works at both weak and strong coupling regimes.

Numerical calculations support experimental results.

Abstract

Recent experiments have demonstrated that measurements of the entropy change associated with the addition of electrons to semiconductor- and graphene-based quantum dots accurately quantify the spin and orbital degeneracy of the states into which they are added. However, measuring more exotic entropies requires probing the entropy change of an entire system in response to an added particle. Here, we demonstrate that Maxwell relation-based measurements probe not only the entropy change associated with the added electron but also that of the surrounding system as it responds to that electron. Using a pair of capacitively coupled GaAs quantum dots, we show that charge measurements on one dot reveal entropy changes associated with the entire two-dot system, both at weak dot--reservoir coupling where microstate counting applies and at stronger coupling where numerical renormalization group calculations are required.