Entropy Measurement of a Strongly Coupled Quantum Dot

Timothy Child, Owen Sheekey, Silvia Lüscher, Saeed Fallahi, Geoffrey C. Gardner, Michael Manfra, Andrew Mitchell, Eran Sela, Yaakov Kleeorin, Yigal Meir, and Joshua Folk

Phys. Rev. Lett. 129, 227702 – Published 22 November 2022

Abstract

The spin $1 / 2$ entropy of electrons trapped in a quantum dot has previously been measured with great accuracy, but the protocol used for that measurement is valid only within a restrictive set of conditions. Here, we demonstrate a novel entropy measurement protocol that is universal for arbitrary mesoscopic circuits and apply this new approach to measure the entropy of a quantum dot hybridized with a reservoir. The experimental results match closely to numerical renormalization group (NRG) calculations for small and intermediate coupling. For the largest couplings investigated in this Letter, NRG calculations predict a suppression of spin entropy at the charge transition due to the formation of a Kondo singlet, but that suppression is not observed in the experiment.

Received 27 April 2022
Accepted 28 October 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.227702

Physics Subject Headings (PhySH)

Entropy Kondo effect Mesoscopics

Nanostructures Quantum dots

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Timothy Child ^1,2,*, Owen Sheekey^1,2, Silvia Lüscher^1,2, Saeed Fallahi^3,4, Geoffrey C. Gardner^4,5, Michael Manfra^3,4,6,5, Andrew Mitchell^7,8, Eran Sela⁹, Yaakov Kleeorin¹⁰, Yigal Meir^11,12, and Joshua Folk ^1,2,†

¹Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada
²Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T1Z1, Canada
³Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
⁴Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
⁵School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
⁶Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
⁷School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
⁸Centre for Quantum Engineering, Science, and Technology, University College Dublin, Dublin 4, Ireland
⁹Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, IL-69978 Tel Aviv, Israel
¹⁰Center for the Physics of Evolving Systems, University of Chicago, Chicago, Illinois 60637, USA
¹¹Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
¹²The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel