Heat capacity for systems with excited-state quantum phase transitions

Abstrakt

Heat capacities of model systems with finite numbers of effective degrees of freedom are evaluated using canonical and microcanonical thermodynamics. Discrepancies between both approaches, which are observed even in the infinite-size limit, are particularly large in systems that exhibit an excited-state quantum phase transition.

The corresponding irregularity of the spectrum generates a singularity in the microcanonical heat capacity and affects smoothly the canonical heat capacity.

Klíčová slova

• Canonical and microcanonical heat capacity
• Thermodynamic systems with low numbers of degrees of freedom
• Excited-state quantum phase transitions