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記
日時：２０１８年１１月１６日（金）１３時３０分〜
場所：東京大学 生産技術研究所 千葉実験所 研究実験棟Ｉn210号室
道程：http://hatano-lab.iis.u-tokyo.ac.jp/access.html
講師：中川大也さん（理研）
演題：Non-Hermitian Kondo effect in ultracold alkaline-earth atoms
要旨：Isolated quantum systems are governed by unitary dynamics and described by Hermitian Hamiltonians, yet no quantum system is completely isolated in reality and dissipation is ubiquitous in nature. The non-unitary dynamics of open quantum systems permits an effective description based on non-Hermitian Hamiltonians under an appropriate condition [1,2]. While various quantum phenomena inherent in open systems have been discovered in single-particle non-Hermitian quantum mechanics, many-body physics with interparticle interactions largely remains unexplored, partly due to the lack of feasible experimental realizations. Thus, it is an important open problem to search for hitherto unnoticed quantum many-body effects in non-Hermitian systems and their experimental platforms.
In this talk, we show that an experimental setup with ultracold alkaline-earth atoms [3] provides a non-Hermitian extension of a paradigmatic quantum many-body effect: the Kondo effect [4]. In this system, inelastic collisions and the associated atom loss have been experimentally observed. Using a quantum master equation approach, we derive a non-Hermitian Kondo Hamiltonian that describes the effect of the inelastic collisions with a complex-valued Kondo interaction. By renormalization-group (RG) analysis of the non-Hermitian Kondo model, we reveal that the non-Hermiticity induces a quantum phase transition associated with anomalous reversion of RG flows which violates the g-theorem of unitary theory. Furthermore, we find an exact solution of the non-Hermitian Kondo model by using a generalized Bethe-ansatz method. The critical line obtained from the exact solution shows a good agreement with the prediction of the RG result.
参考文献
[1] A. J. Daley, Adv. Phys. 63, 77 (2014).
[2] J. Dalibard et al., Phys. Rev. Lett. 68, 580 (1992).
[3] L. Riegger et al., Phys. Rev. Lett. 120, 143601 (2018).
[4] M. Nakagawa, N. Kawakami, and M. Ueda, arXiv:1806.04039 (to appear in Phys. Rev. Lett.).
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李 宰河
〒277-8574 千葉県柏市柏の葉5-1-5
東京大学生産技術研究所
e-mail: lee@iis.u-tokyo.ac.jp
Tel: 04-7136-6977
Fax: 04-7136-6978
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