Quantum phase transitions in Bose–Fermi systems

Quantum phase transitions in a system of N bosons with angular momentum L = 0, 2 (s, d) and a single fermion with angular momentum j are investigated both classically and quantum mechanically. It is shown that the presence of the odd fermion strongly influences the location and nature of the phase transition, especially the critical value of the control parameter at which the phase transition occurs. Experimental evidence for the U(5)–SU(3) (spherical to axially-deformed) transition in odd–even nuclei is presented.

Research highlights► We study quantum phase transitions in a system of N bosons and a single-j fermion. ► Classical order parameters and correlation diagrams of quantum levels are determined. ► The odd fermion strongly influences the location and nature of the phase transition. ► Experimental evidence for the U(5)–SU(3) transition in odd–even nuclei is presented.