First-Order Quantum Phase Transition for Dicke Model Induced by Atom-Atom Interaction

Zhao Xiu-Qin^{1, 2}, Liu Ni^{1, †}, Liang Jiu-Qing¹

The first-order derivative of the average ground-state energy (a) and the second-order derivative (b) as the function of the collective coupling strength and the atom-atom interaction () with .