Thermodynamic analogy for quantum phase transitions at zero temperature

We propose a relationship between thermodynamic phase transitions and groundstate quantum phase transitions in systems with variable Hamiltonian parameters. It is based on a link between zeros of the canonical partition function at complex temperatures and exceptional points of a quantum Hamiltonian in the complexextended parameter space. This approach is applied in the interacting boson model, where it is shown to properly distinguish the firstand second-order phase transitions.