Quasiperiodic quantum heat engines with a mobility edge

Abstract

Steady-state thermoelectric machines convert heat into work by driving a thermally generated charge current against a voltage gradient. In this work, we propose a new class of steady-state heat engines operating in the quantum regime, where a quasiperiodic tight-binding model that features a mobility edge forms the working medium. In particular, we focus on a generalization of the paradigmatic Aubry-André-Harper (AAH) model, known to display a single-particle mobility edge that separates the energy spectrum into regions of completely delocalized and localized eigenstates. Remarkably, these two regions can be exploited in the context of steadystate heat engines as they correspond to ballistic and insulating transport regimes. This model also presents the advantage that the position of the mobility edge can be controlled via a single parameter in the Hamiltonian. We exploit this highly tunable energy filter, along with the peculiar spectral structure of quasiperiodic systems, to demonstrate large thermoelectric effects, exceeding existing predictions by several orders of magnitude. This opens the route to a new class of highly efficient and versatile quasiperiodic steady-state heat engines, with a possible implementation using ultracold neutral atoms in bichromatic optical lattices. arXiv:1908.05139v2 [cond-mat.dis-nn]

Dephasing-enhanced performance in quasiperiodic thermal machines

“…However, the choice of γ is largely immaterial. It has previously been shown that within linear response and WBL approximation, modifying γ in this set-up rescales the currents without qualitatively affecting the transport behaviour [14].…”

“…If transport is blocked within a certain energy window, the Seebeck coefficient S increases dramatically. This is generally achieved by tuning the thermodynamic variables of the reservoirs [87,88] or by choosing samples that would exhibit strongly energy dependent transmission properties, for example in presence of a mobility edge [2,13,14].…”

“…This picture is modified due to the inevitable presence of disorder. In mesoscopic physics the interplay between transport and disorder is well studied and in particular this interplay has been shown to enhance the thermoelectric performances of disordered low dimensional systems [2][3][4][5][6][7][8][9][10][11][12][13][14].…”

“…Quasiperiodic systems have also been shown to offer potential applications in quantum heat management, e.g. as rectifiers [56][57][58] or as highly efficient working media for thermoelectric engines [14]. Here we ask if the inevitable presence of dephasing noise can be used to further engineer their thermal capabilities.…”

Waiting-times statistics in boundary driven free fermion chains

“…In fact, as illustrated in Refs. [65][66][67][68][69][70][71], quasi-periodic non-interacting chains can exhibit any kind of transport, not only ballistic [66,68,72,73]. A study of WTDs for these models will be the subject of future work.…”