Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 56: Correlated Electrons: Quantum-Critical Phenomena – Theory

TT 56.7: Talk

Wednesday, March 18, 2015, 11:00–11:15, A 053

Universal phase diagram of quantum dissipative many-body systems — •Gianluca Rastelli — Fachbereich Physik & Zukunftskolleg, Universität Konstanz, D-78457 Konstanz, Germany

The interplay between quantum dissipation and interactions in quantum many-body systems can give rise to a wealth of novel phenomena. The one-dimensional coplanar rotor model (also known as quantum phase model) is a paradigmatic model for studying quantum phase transitions with dissipative coupling to an external bath. It can describe, for instance, one-dimensional chains of superconducting islands connected by Josephson junctions and shunt resistances [1]. At zero temperature, a quantum phase transition occurs by tuning the interaction strength between the phases. When the system is coupled to the environment, the common accepted scenario is that the dissipation suppresses the quantum fluctuations and, therefore, enhances the classical ground state characterised by long-range order [2,3]. Contrary to previous studies, I focus on a system which is coupled to the environment with a dissipative interaction designed in way to reduce the quantum fluctuations of the conjugate variables of the local phases. I will show that this anomalous dissipation leads to a reversed behaviour of the phase diagram: Increasing the dissipation causes a stabilisation of the disordered quantum ground state.

[1] R. Fazio and H. van der Zant, Phys. Rep. 355, 235 (2001).

[2] S. Chakravarty, G.L. Ingold, S. Kivelson, and A. Luther,

Phys. Rev. Lett. 56, 2303 (1986).

[3] P. A. Bobbert, R. Fazio, G. Schön, and G. T. Zimanyi,

Phys. Rev. B 41, 4009 (1990).