Phase transitions and critical behaviour

David A. Lavis, Roman Frigg

Wang N. Wang, Pan Jin-Sheng

The phase transition-like behaviour of bulk polaron is investigated. We find that there exists a certain critical temperature T c and the phase transition behaviour below T c is different from that above T c .

Yang-Yang Chen, Yao-zong Jiang, Xin Guan +1 more

A central quantity of importance for ultracold atoms is contact, which measures two-body correlations at short distances in dilute systems. It appears in universal relations among thermodynamic quantities, such as large momentum tails, energy and dynamic structure factors, through the renowned Tan relations. However, a conceptual question remains open as to whether or not contact can signify phase transitions that are insensitive to short-range physics. Here we show that, near a continuous classical or quantum phase transition, contact exhibits a variety of critical behaviours, including scaling laws and critical exponents that are uniquely determined by the universality class of the phase transition, and a constant contact per particle. We also use a prototypical exactly solvable model to demonstrate these critical behaviours in one-dimensional strongly interacting fermions. Our work establishes an intrinsic connection between the universality of dilute many-body systems and universal critical phenomena near a phase transition.

Per-Anker Lindgård

Arno Holz, J.T.N. Medeiros

Quantum effects on the static critical behaviour of an isotropic n-vector model undergoing a displacement-type phase transition are studied at T c and to O(1/n). For T c not=0 there is no quantum effect on eta , and for T c =0 one gets eta =0 for d>3, and for 2<d<3 eta is due to quantum fluctuations, implying that it assumes a different value than in the classical case. The dynamical behaviour of the system violates the dynamic scaling hypothesis.