Wydarzenia

Seminarium "Coherence-Correlations-Complexity" (KFT, PWr)

Nonequilibrium heat transport in an exactly solvable quantum-critical model

prof. Tomáš Novotný

Wydział Matematyki i Fizyki Uniwersytetu Karola w Pradze

I study heat transport in an exactly solvable modification of the nonequilibrium transverse-field Ising-chain model originally studied by M. Vogl, G. Schaller, and T. Brandes in Phys. Rev. Lett. 109, 240402 (2012) & J. Phys. Cond. Matt. 26, 265001 (2014). The spin-chain model can be fermionized by the Jordan- Wigner transform to equivalent non-interacting fermions and consequently exactly diagonalized for any value of the model parameters, in particular, the coupling to the heat spin baths. I verify the conclusions of the approximate master-equation treatment a la Vogl et al. in the limit of very weak coupling to reservoirs and extend those results to finite coupling strengths. It turns out that for finite couplings the fate of the quantum-phase-transition-like singularities in the heat current depends crucially on the way, how the thermodynamic limit is performed, more specifically, how the coupling to the boundary reservoirs is treated. I will discuss the physical interpretation of the importance of the boundary conditions in the transport and will also comment on the relation to the “conventional” equilibrium QPT via the behavior of the correlation functions. I will argue that the non-equilibrium phenomenon appears to be actually closer to the Electronic Topological Transitions (cf. Ya. M. Blanter et al., Physics Reports 245, 159 (1994)) than standard QPTs.