Ensemble inequivalence in long-range quantum systems

Understand

Ensemble inequivalence, i.e.

• the possibility of observing different thermodynamic properties depending on the statistical ensemble which describes the system, is one of the hallmarks of long-range physics, which has been demonstrated in numerous classical systems.
• Here, an example of ensemble inequivalence of a long-range quantum ferromagnet is presented.
• While the $T=0$ microcanonical quantum phase-diagram coincides with that of the canonical ensemble, the phase-diagrams of the two ensembles are different at finite temperature.