Mainz 2017 – scientific programme
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A: Fachverband Atomphysik
A 28: Ultracold Plasmas, Rydberg Systems and Molecules (with Q)
A 28.2: Talk
Thursday, March 9, 2017, 11:30–11:45, P 104
Multicritical behavior in dissipative Ising models — •Vincent Overbeck1, Mohammad Maghrebi2, Alexey Gorshkov2, and Hendrik Weimer1 — 1Institut für Theoretische Physik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany — 2Joint Quantum Institute and Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, Maryland 20742, USA
Physical phenomena of dissipative quantum many-body systems can be quite different from those of their equilibrium counterparts. We analyze a Z2- preserving dissipative Ising model using a variational principle [1,2]. In the steady state phase diagram, we find in addition to a continuous transition, a first order transition between an ordered and an unordered phase and a tricritical point. We extend our analysis by a Ginzburg-Landau approach, verifying in detail the validity of our product state ansatz. We show that fluctuations due to spatial inhomogeneities are produced in the same way as in equilibrium, allowing us to determine an upper critical dimension, above which fluctuations in the multicritical regime vanish and the critical exponents of our product state theory become correct. Finally, we will present a renormalization group analysis of our functional, investigating how a one loop correction influences the position of the tricritical point.
[1] H. Weimer, Variational Principle for Steady States of Dissipative Quantum Many-Body Systems, Phys. Rev. Lett. 114, 040402 (2015).
[2] H. Weimer, Variational analysis of driven-dissipative Rydberg gases, Phys. Rev. A 91, 063401 (2015).