Quasiperiodic quantum heat engines with a mobility edge

Cecilia Chiaracane,John Goold,Géraldine Haack,Archak Purkayastha,Mark T Mitchison

doi:10.1103/physrevresearch.2.013093

Cecilia Chiaracane, John Goold + Show 3 more

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https://doi.org/10.1103/physrevresearch.2.013093

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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 quasi-periodic tight-binding model that features a mobility edge forms the working medium. In particular, we focus on a generalization of the paradigmatic Aubrey-Andr\'e-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 steady-state 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 quasi-periodic steady-state heat engines, with a possible implementation using ultracold neutral atoms in bichromatic optical lattices.

Highlights

Scientific activity in the area of thermal machines has been boosted in recent years by the increasing importance that society is placing on sustainable energy
We focus on the generalized AAH (GAAH) model recently introduced in Ref. [34], for which an exact analytical expression for the mobility edge is known
We see that the mobility edge and the clusters of ballistic states lying above it generally give rise to a highly asymmetric transmission profile, which is conducive to a large thermoelectric response

Summary

Introduction

Scientific activity in the area of thermal machines has been boosted in recent years by the increasing importance that society is placing on sustainable energy. Thermoelectric engines, in particular, do not rely on macroscopic moving parts. Instead, they convert heat into power through nonequilibrium steady-state currents of microscopic particles, e.g., electrons or atoms, flowing between two reservoirs. Bulk thermoelectrics are generally quite inefficient [11]. This drawback, together with the unprecedented level of control achieved in nanotechnology, has fuelled both experimental and theoretical research to identify and characterize new nanoscale systems to be harnessed as efficient thermal engines [12,13,14,15,16,17]

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