Reentrant random quantum Ising antiferromagnet

Abstract

We consider the quantum Ising chain with uniformly distributed random antiferromagnetic couplings ( 1 ≤ J i ≤ 2 ) and uniformly distributed random transverse fields ( Γ 0 ≤ Γ i ≤ 2 Γ 0 ) in the presence of a homogeneous longitudinal field, h . Using different numerical techniques (density-matrix renormalization group, combinatorial optimization, and strong disorder renormalization group methods) we explore the phase diagram, which consists of an ordered and a disordered phase. At one end of the transition line ( h = 0 , Γ 0 = 1 ) there is an infinite disorder quantum fixed point, while at the other end ( h = 2 , Γ 0 = 0 ) there is a classical random first-order transition point. Close to this fixed point, for h > 2 and Γ 0 > 0 there is a reentrant ordered phase, which is the result of quantum fluctuations by means of an order through disorder phenomenon.