Quantum phase transitions and entanglement entropy in a non-Hermitian Jaynes-Cummings model
arXiv:2506.23356 · doi:10.1016/j.aop.2026.170484
Abstract
In this paper, we describe some interesting properties of a non-Hermitian Jaynes-Cummings model. For this particular model, it is known that the Hilbert space can be described by infinitely-many two-dimensional invariant (closed) subspaces, together with the global ground state. We expose the appearance of exceptional points on such two-dimensional subspaces, together with quantum phase transitions marking the transition from real to complex eigenvalues. We also compute the spin-oscillator entanglement entropy on each invariant subspace to show that the two phases can be distinguished by their distinct entanglement-entropy profiles.
v1: 9 pages, 5 figures; v2: 18 pages, 3 figures, several errors corrected and substantially revised; v3: Published in Annals of Physics; the arXiv version also includes a clarifying footnote added post-publication, along with two minor edits to Sec. 5
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