Dephasing-enhanced performance in quasiperiodic thermal machines

Abstract

Understanding and controlling quantum transport in low-dimensional systems is pivotal for heat management at the nanoscale. One promising strategy to obtain the desired transport properties is to engineer particular spectral structures. In this work we are interested in quasiperiodic disorder -incommensurate with the underlying periodicity of the lattice -which induces fractality in the energy spectrum. A well known example is the Fibonacci model which, despite being non-interacting, yields anomalous diffusion with a continuously varying dynamical exponent smoothly crossing over from superdiffusive to subdiffusive regime as a function of potential strength. We study the finite-temperature electric and heat transport in this model in the absence and in the presence of dephasing. Dephasing causes both thermal and electric transport to become diffusive, thereby making thermal and electrical conductivities finite in the thermodynamic limit. Thus, in the subdiffusive regime it leads to enhancement of transport. We find that the thermal and electric conductivities have multiple peaks as a function of dephasing strength. Remarkably, we observe that the thermal and electrical conductivities are not proportional to each other, a clear violation of Wiedemann-Franz law, and the position of their maxima can differ. We argue that this feature can be utilized to enhance performance of quantum thermal machines. In particular, we show that by tuning the strength of the dephasing we can enhance the performance of the device in regimes where it acts as an autonomous refrigerator.

Quantum transport in quasi-periodic lattice systems in presence of Büttiker probes

“…The popular quasi-periodic lattice systems, namely, the Aubry-André-Harper (AAH), its generalised version GAAH model and the Fibonacci model [21,22] have been studied extensively in the context of boundary driven dissipative quantum transport [23][24][25][26][27][28][29]. Further studies have started to emerge to understand the environment induced effects on transport [30][31][32][33][34][35][36][37] in such systems. Very recently, following the local Lindblad master equation formalism, the steady-state transport properties due to dephasing noise were analyzed for AAH and Fibonacci models [34].…”

“…Following a similar approach, the effect of dephasing noise on transport was studied in presence of mobility edge [35]. Another recent work [36] focused on understanding thermoelectric transport properties for Fibonacci type model using the first principle Büttiker voltage-temperature probe approach, [38][39][40][41] where it was shown that noise induced processes can lead to a better thermoelectric performance in certain regimes of transport. Note that, such a Büttiker probe technique was used extensively in the past to understand effective many-body transport properties in setups like molecular junctions [42][43][44][45][46][47][48][49], quantum dots [50], lattice models of oscillators [51][52][53] etc.…”