Condensed Matter Physics, 2009, vol. 12, No. 3, pp. 519-530

Title: Revealing novel quantum phases in quantum antiferromagnets on random lattices
  R. Yu (Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA;
Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 32831, USA)
  S. Haas (Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA) ,
  T. Roscilde (Laboratoire de Physique, École Normale Supérieure de Lyon, 46 Allée d'Italie, 69003 Lyon, France)

Quantum magnets represent an ideal playground for the controlled realization of novel quantum phases and of quantum phase transitions. The Hamiltonian of the system can be indeed manipulated by applying a magnetic field or pressure on the sample. When doping the system with non-magnetic impurities, novel inhomogeneous phases emerge from the interplay between geometric randomness and quantum fluctuations. In this paper we review our recent work on quantum phase transitions and novel quantum phases realized in disordered quantum magnets. The system inhomogeneity is found to strongly affect phase transitions by changing their universality class, giving the transition a novel, quantum percolative nature. Such transitions connect conventionally ordered phases to unconventional, quantum disordered ones - quantum Griffiths phases, magnetic Bose glass phases - exhibiting gapless spectra associated with low-energy localized excitations.

Key words: Heisenberg antiferromagnets, quantum disorder, geometric randomness, percolation, Bose glass
PACS: 75.10.Jm, 75.10.Nr, 75.40.Cx, 64.60.Ak
Comments: Figs. 9, Refs. 34, Tabs. 0

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