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Quantum phase transitions: effects of disorder and dissipation


The purpose of this project is to study the effects of disorder and correlation in various quantum phase transitions. The reason for such is manyfold. Many metalic compounds defy Landau's Fermi liquid theory. Among the reasons for such are the effects of disorder and magnetic instability on the quasiparticles due to the proximity of a quantum critical point. It is then important for the development of new materials as well for new theoretical frameworks that we understand the interplay between disorder and dissipation in critical systems. In this line of research, we will study many itinerant magnetic models in the presence of disorder. We will use mainly a strong disorder renormalization group technique which, in principle, is powerful enough to obtain nonperturbative effects of interactions near a critical point in which disorder is intrinsically strong. Another motivation is to study disordered quantum magnetism. In many cases, disorder destabilize the clean magnetic phase yielding to qualitatively new ones. Precisely, we will be interested in the many variations of the Heisenberg model with symmetry larger than SU(2). Recently, the effect of these larger symmetries have been seen experimentally in cold-atoms systems in which the parameters of the Hamiltonian are well controlled, including the effects of disorder which can be controlled without precedents via laser speckle. In the great majority, these projects will be tackled numerically. It is thus important that we have competitive computational resources. Great part of the budget of this project is thus to acquire such resources. (AU)

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Scientific publications (5)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
VOJTA, THOMAS; HOYOS, JOSE A.; MOHAN, PRIYANKA; NARAYANAN, RAJESH. Influence of super-ohmic dissipation on a disordered quantum critical point. JOURNAL OF PHYSICS-CONDENSED MATTER, v. 23, n. 9, SI, . (10/03749-4)
HRAHSHEH, FAWAZ; HOYOS, JOSE A.; VOJTA, THOMAS. Rounding of a first-order quantum phase transition to a strong-coupling critical point. Physical Review B, v. 86, n. 21, . (10/03749-4)
HOYOS, JOSE A.; VOJTA, THOMAS. Dissipation effects in random transverse-field Ising chains. Physical Review B, v. 85, n. 17, p. 174403, . (10/03749-4)
AL-ALI, MANAL; HOYOS, JOSE A.; VOJTA, THOMAS. Percolation transition in quantum Ising and rotor models with sub-Ohmic dissipation. Physical Review B, v. 86, n. 7, . (10/03749-4)
DEL MAESTRO, ADRIAN; ROSENOW, BERND; HOYOS, JOSE A.; VOJTA, THOMAS. Dynamical Conductivity at the Dirty Superconductor-Metal Quantum Phase Transition. Physical Review Letters, v. 105, n. 14, . (10/03749-4)

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