Title: Random Ising chain in transverse and longitudinal fields: Strong disorder RG study
Author(s):

	T. Pető (Institute of Theoretical Physics, Szeged University, H-6720 Szeged, Hungary),
	F. Iglói (Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, H-1525 Budapest, P.O. Box 49, Hungary; Institute of Theoretical Physics, Szeged University, H-6720 Szeged, Hungary ),
	I. A. Kovács (Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA; Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL 60208, USA)

Motivated by the compound LiHo_xY_1-xF₄, we consider the Ising chain with random couplings and in the presence of simultaneous random transverse and longitudinal fields, and study its low-energy properties at zero temperature by the strong disorder renormalization group approach. In the absence of longitudinal fields, the system exhibits a quantum-ordered and a quantum-disordered phase separated by a critical point of infinite disorder. When the longitudinal random field is switched on, the ordered phase vanishes and the trajectories of the renormalization group are attracted to two disordered fixed points: one is characteristic of the classical random field Ising chain, the other describes the quantum disordered phase. The two disordered phases are separated by a separatrix that starts at the infinite disorder fixed point and near which there are strong quantum fluctuations.

Key words: magnetic systems, disordered systems, quantum spin models, phase transitions, spin glasses

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