Quantum geometric tensor and quantum phase transitions in the Lipkin-Meshkov-Glick model

D Gutiérrez-Ruiz, D Gonzalez, J Chávez-Carlos… - Physical Review B, 2021 - APS
We study the quantum metric tensor and its scalar curvature for a particular version of the
Lipkin-Meshkov-Glick model. We build the classical Hamiltonian using Bloch coherent states
and find its stationary points. They exhibit the presence of a ground-state quantum phase
transition where a bifurcation occurs, showing a change in stability associated with an
excited-state quantum phase transition. Symmetrically, for a sign change in one Hamiltonian
parameter, the same phenomenon is observed in the highest-energy state. Employing the …
We study the quantum metric tensor and its scalar curvature for a particular version of the Lipkin-Meshkov-Glick model. We build the classical Hamiltonian using Bloch coherent states and find its stationary points. They exhibit the presence of a ground-state quantum phase transition where a bifurcation occurs, showing a change in stability associated with an excited-state quantum phase transition. Symmetrically, for a sign change in one Hamiltonian parameter, the same phenomenon is observed in the highest-energy state. Employing the Holstein-Primakoff approximation, we derive analytic expressions for the quantum metric tensor and compute the scalar and Berry curvatures. We contrast the analytic results with their finite-size counterparts obtained through exact numerical diagonalization and find excellent agreement between them for large sizes of the system in a wide region of the parameter space except in points near the phase transition where the Holstein-Primakoff approximation ceases to be valid.
American Physical Society