2026-06-07T16:52:27Zhttps://docta.ucm.es/rest/oai/requestoai:docta.ucm.es:20.500.14352/45412023-08-26T06:55:17Zcom_20.500.14352_14col_20.500.14352_15
Docta Complutense
author
Corps, Angel L.
author
Relaño Pérez, Armando
2023-06-16T14:17:25Z
2023-06-16T14:17:25Z
2021-09-24
0031-9007
10.1103/PhysRevLett.127.130602
https://hdl.handle.net/20.500.14352/4541
https://doi.org/10.1103/PhysRevLett.127.130602
https://journals.aps.org/
We propose that a broad class of excited-state quantum phase transitions (ESQPTs) gives rise to two different excited-state quantum phases. These phases are identified by means of an operator (C) over cap, which is a constant of motion in only one of them. Hence, the ESQPT critical energy splits the spectrum into one phase where the equilibrium expectation values of physical observables crucially depend on this constant of motion and another phase where the energy is the only relevant thermodynamic magnitude. The trademark feature of this operator is that it has two different eigenvalues +/- 1, and, therefore, it acts as a discrete symmetry in the first of these two phases. This scenario is observed in systems with and without an additional discrete symmetry; in the first case, (C) over cap explains the change from degenerate doublets to nondegenerate eigenlevels upon crossing the critical line. We present stringent numerical evidence in the Rabi and Dicke models, suggesting that this result is exact in the thermodynamic limit, with finite-size corrections that decrease as a power law.
eng
Constant of Motion Identifying Excited-State Quantum Phases
journal article
URL
https://docta.ucm.es/bitstreams/4e8fb324-0fb5-43fb-a359-cda1b2e056c5/download
File
MD5
88dba7409391884d865f5c5682a79c43
543387
application/pdf
Relaño69libre.pdf