Continuous Phase Transition without Gap Closing in Non-Hermitian Quantum Many-Body Systems

Norifumi Matsumoto, Kohei Kawabata, Yuto Ashida, Shunsuke Furukawa, Masahito Ueda

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Contrary to the conventional wisdom in Hermitian systems, a continuous quantum phase transition between gapped phases is shown to occur without closing the energy gap Δ in non-Hermitian quantum many-body systems. Here, the relevant length scale ζ≃vLR/Δ diverges because of the breakdown of the Lieb-Robinson bound on the velocity (i.e., unboundedness of vLR) rather than vanishing of the energy gap Δ. The susceptibility to a change in the system parameter exhibits a singularity due to nonorthogonality of eigenstates. As an illustrative example, we present an exactly solvable model by generalizing Kitaev's toric-code model to a non-Hermitian regime.

Original languageEnglish
Article number260601
JournalPhysical review letters
Volume125
Issue number26
DOIs
Publication statusPublished - 2020 Dec 21

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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