RT Journal Article
T1 Constant of Motion Identifying Excited-State Quantum Phases
A1 Corps, Angel L.
A1 Relaño Pérez, Armando
AB 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.
PB American Physical Society
SN 0031-9007
YR 2021
FD 2021-09-24
LK https://hdl.handle.net/20.500.14352/4541
UL https://hdl.handle.net/20.500.14352/4541
LA eng
NO © 2021 American Physical Society. We acknowledge financial support from Ministerio de Ciencia, Innovación y Universidades/Agencia Estatal de Investigación (MCIU/AEI/FEDER, EU) under Grant No. PGC2018-094180-B-I00.
NO Ministerio de Ciencia e Innovación (MICINN)/FEDER
DS Docta Complutense
RD 12 abr 2025