2025-12-25 東京科学大学
図1. スピン対破壊効果の模式図。粒子のスピンが上向きの粒子が右に行きやすく、下向きの粒子が左に行きやすい状況を描写している。
＜関連情報＞
- https://www.isct.ac.jp/ja/news/2cc77j8aqtxa
- https://www.isct.ac.jp/plugins/cms/component_download_file.php?type=2&pageId=&contentsId=1&contentsDataId=2922&prevId=&key=1f08daf518007ab6bdd60ca93e0fb5f5.pdf
- https://journals.aps.org/prl/abstract/10.1103/ntjf-zb2v
スピン脱対化誘起による例外的なフェルミオン超流動 Spin-Depairing-Induced Exceptional Fermionic Superfluidity
Soma Takemori, Kazuki Yamamoto, and Akihisa Koga
Physical Review Letters
DOI: https://doi.org/10.1103/ntjf-zb2v
Abstract
We investigate the non-Hermitian (NH) attractive Hubbard model with spin depairing, which is a spin-resolved asymmetric hopping that nonreciprocally operates spins in the opposite direction. We find that spin depairing stabilizes a superfluid state unique to the NH system. This phase is characterized not only by a finite order parameter, but also by the emergence of exceptional points (EPs) in the momentum space—a feature that starkly contrasts with previously discussed NH fermionic superfluidity, where EPs are absent within the superfluid state and emerge only at the onset of the superfluid breakdown. We uncover the rich mechanism underlying this “exceptional fermionic superfluidity” by analyzing the interplay between EPs and the effective density of states of the complex energy dispersion. Furthermore, we reveal that the exceptional superfluid state breaks down induced by strong spin depairing on the cubic lattice, while it remains robust on the square lattice.
