The CQT team


Picture taken at the end of April 2010 in "Friedenspark" next to the previous location of the Institute



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Abstract: We consider the quantum Ising chain with uniformly distributed random antiferromagnetic couplings (1 ≤ Ji ≤ 2) and uniformly distributed random transverse fields (Γ0 ≤ Γi ≤ 2Γ0) in the presence of a homogeneous longitudinal field, h. Using different numerical techniques (DMRG, combinatorial optimisation and strong disorder RG methods) we explore the phase diagram, which consists of an ordered and a disordered phase. At one end of the transition line (h = 0, Γ0 = 1) there is an infinite disorder quantum fixed point, while at the other end (h = 2,Γ0 = 0) there is a conventional classical random fixed point. Close to this fixed point, for h > 2 and Γ0 > 0 there is a reentrant ordered phase, which is the result of quantum fluctuations through an order through disorder phenomenon.