I this talk I will address the general problem of energy transport in a microscopic network of coupled harmonic oscillators, where it is the goal, for example, to deliver energy from a quantum generator to a quantum engine. I will show that transport in such systems differs strongly from the usual Ohm's or Fourier's law and exhibits various anomalies, which arise from the competition between coherent and incoherent processes in combination with nonlinear saturation effects. Specifically, one finds that such networks exhibit a non-equilibrium phase transition between a noise-dominated and a coherent transport regime. This transition is closely related to the phenomenon of PT-symmetry breaking in classical gain-loss systems, but is identified here as a very generic mechanism in active quantum networks. As an outlook I will show that in dissipative spin systems the same PT-symmetry breaking mechanism results in novel types of phase transitions, which do not exhibit the usual features of phase co-existence or symmetry-breaking.
Seminar; Lecture; Colloquium
Kollektorn, lecture room, Kemivägen 9, MC2-huset
23 January, 2020, 15:15
23 January, 2020, 16:00