Orthoexciton-to-paraexciton conversion rate in Cu2O at sub-Kelvin temperatures
Abstract
We measured the conversion rate from 1s orthoexcitons to 1s paraexcitons in Cu2O below 1 K using a dilution refrigerator. To determine the conversion rate, we performed time-resolved luminescence spectroscopy of 1s orthoexcitons and 1s paraexcitons confined in a strain-induced trap potential. From the time evolution of the Γ3−-LO-phonon-assisted luminescence of 1s orthoexcitons, we obtained a conversion rate of 5.9 × 107 s−1 at a mixing-chamber temperature of 64 mK under an applied stress of 2.2 kbar. Between 64 and 800 mK, the conversion rate depends only weakly on temperature, and it is less than half of the value of 1.6 × 108 s−1 reported at 2 K under the same applied stress. The conversion rate therefore continues to decrease below 2 K, contrary to the previous expectation that it becomes nearly constant below about 1.7 K. We discuss these results in terms of the momentum distribution of orthoexcitons, which does not reach equilibrium with the lattice during the conversion at these low temperatures. These findings call for a theory that accounts for both the small magnitude of the conversion rate and its weak temperature dependence below 1 K.
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BibTeX
@misc{morita2026orthoexcitontoparaexciton,
title = {{Orthoexciton-to-paraexciton conversion rate in Cu$_2$O at sub-Kelvin temperatures}},
author = {Yusuke Morita and Yukihiro Akiyama and Yuki Haita and Yuga Hirota and Kosuke Yoshioka},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.17812},
eprint = {2610.17812},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.17812},
}
RIS
TY - UNPB
TI - Orthoexciton-to-paraexciton conversion rate in Cu_2O at sub-Kelvin temperatures
AU - Yusuke Morita
AU - Yukihiro Akiyama
AU - Yuki Haita
AU - Yuga Hirota
AU - Kosuke Yoshioka
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.17812
UR - https://arxiv.org/abs/2610.17812
AB - We measured the conversion rate from 1s orthoexcitons to 1s paraexcitons in Cu_2O below 1 K using a dilution refrigerator. To determine the conversion rate, we performed time-resolved luminescence spectroscopy of 1s orthoexcitons and 1s paraexcitons confined in a strain-induced trap potential. From the time evolution of the Γ_3^−-LO-phonon-assisted luminescence of 1s orthoexcitons, we obtained a conversion rate of 5.9 × 10^7 s^−1 at a mixing-chamber temperature of 64 mK under an applied stress of 2.2 kbar. Between 64 and 800 mK, the conversion rate depends only weakly on temperature, and it is less than half of the value of 1.6 × 10^8 s^−1 reported at 2 K under the same applied stress. The conversion rate therefore continues to decrease below 2 K, contrary to the previous expectation that it becomes nearly constant below about 1.7 K. We discuss these results in terms of the momentum distribution of orthoexcitons, which does not reach equilibrium with the lattice during the conversion at these low temperatures. These findings call for a theory that accounts for both the small magnitude of the conversion rate and its weak temperature dependence below 1 K.
ER -