Entropy spectroscopy of a tunable two-site Hubbard molecule
Abstract
Determining which microscopic states remain thermally active when tunneling and interactions compete is a central question in Hubbard physics. Here we develop an entropy measurement protocol for a double quantum dot, extending the charge-based approach established for a single dot, and measure the total entropy of a tunable two-site Hubbard molecule realized in a GaAs double dot. By shifting both dot levels together at fixed detuning, the entropy is correctly probed with only a single charge sensor. As interdot tunneling increases, the system evolves from two atomic-like dots through hybridized molecular states to a merged single dot. Across this evolution, the entropy decreases as tunnel-induced energy splitting exceeds the thermal energy and suppresses the occupation of higher-energy states. The measurements resolve the diminishing contribution of antibonding states and the changing thermal contributions of hybridized singlet and triplet states, in quantitative agreement with a two-site Hubbard model. By distinguishing states with the same charge configuration but different orbital and spin content, entropy reveals how tunneling and interactions determine the thermally active states of the minimal Hubbard system.
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BibTeX
@misc{kim2026entropy,
title = {{Entropy spectroscopy of a tunable two-site Hubbard molecule}},
author = {Uhjin Kim and Seokyeong Lee and Gibum Yun and Dongsung T. Park and Soobeom Choi and Sangwoo Jeong and Donghoon Kim and V. Umansky and Yunchul Chung and Hyoungsoon Choi and H. -S. Sim and Hyung Kook Choi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17818},
eprint = {2609.17818},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.17818},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Entropy spectroscopy of a tunable two-site Hubbard molecule
AU - Uhjin Kim
AU - Seokyeong Lee
AU - Gibum Yun
AU - Dongsung T. Park
AU - Soobeom Choi
AU - Sangwoo Jeong
AU - Donghoon Kim
AU - V. Umansky
AU - Yunchul Chung
AU - Hyoungsoon Choi
AU - H. -S. Sim
AU - Hyung Kook Choi
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.17818
UR - https://arxiv.org/abs/2609.17818
AB - Determining which microscopic states remain thermally active when tunneling and interactions compete is a central question in Hubbard physics. Here we develop an entropy measurement protocol for a double quantum dot, extending the charge-based approach established for a single dot, and measure the total entropy of a tunable two-site Hubbard molecule realized in a GaAs double dot. By shifting both dot levels together at fixed detuning, the entropy is correctly probed with only a single charge sensor. As interdot tunneling increases, the system evolves from two atomic-like dots through hybridized molecular states to a merged single dot. Across this evolution, the entropy decreases as tunnel-induced energy splitting exceeds the thermal energy and suppresses the occupation of higher-energy states. The measurements resolve the diminishing contribution of antibonding states and the changing thermal contributions of hybridized singlet and triplet states, in quantitative agreement with a two-site Hubbard model. By distinguishing states with the same charge configuration but different orbital and spin content, entropy reveals how tunneling and interactions determine the thermally active states of the minimal Hubbard system.
ER -