2018/11/30 by Orazio Scarlatella, Aashish A. Clerk, Marco Schirò · 1 citation
Physics and Astronomy · #quant-ph #cond-mat.mes-hall #cond-mat.other
paper · pdf · doi:10.1088/1367-2630/ab0ce9
arxiv created 2018/12/03 · arxiv updated 2019/05/22
We study the spectral properties of Markovian driven-dissipative quantum systems, focusing on the nonlinear quantum van der Pol oscillator as a paradigmatic example. We discuss a generalized Lehmann representation, in which single-particle Green's functions are expressed in terms of the eigenstates and eigenvalues of the Liouvillian. Applying it to the quantum van der Pol oscillator, we find a wealth of phenomena that are not apparent in the steady-state density matrix alone. Unlike the steady state, the photonic spectral function has a strong dependence on interaction strength. Further, we find that the interplay of interaction and non-equilibrium effects can result in a surprising "negative density of states", associated with a negative temperature, and we identify two different mechanisms responsible for this phenomenon.