Heat control in mesoscopic conductors - exploiting quantum effects and size confinement
Doctoral thesis, 2020
The central purpose of this thesis is to investigate the impact of specific characteristics of quantum systems, in particular of quantum size confinement, nonequilibrium effects and phase coherence, on heat transport quantities. A better understanding of this impact can lead to an improved control and exploitation of heat. This can be used for the evacuation of heat from the system, cooling, or producing power using waste heat. We propose different experimentally accessible setups. In these setups, we theoretically study transport quantities using a scattering formalism.
We pursue three main study lines in different setups: (i) We investigate phase-dependent heat transport in normal- and superconducting hybrid junctions. We show how disorder influences this, both in simple junctions as well as in a heat circulator. (ii) We analyze thermodynamical machines, which use nonequilibrium states as their resource instead of heat. Such devices show a "demonic behavior" since they seemingly challenge the second law of thermodynamics. (iii) We analyze how to exploit energy filtering of quantum conductors to perform thermoelectric cooling at the example of a quantum spin Hall device in the whole range from linear to nonlinear response.
phase-dependent heat transport
Chalmers, Microtechnology and Nanoscience (MC2), Applied Quantum Physics
Detailed study of nonlinear cooling with two-terminal configurations of topological edge states
Physical Review B,; Vol. 102(2020)
Quantifying nonequilibrium thermodynamic operations in a multiterminal mesoscopic system
Physical Review B,; Vol. 102(2020)
Mesoscopic effects in the heat conductance of superconducting-normal-superconducting and normal-superconducting junctions
PHYSICAL REVIEW B,; Vol. 99(2019)
Phase-coherent heat circulators with normal- or superconducting contacts
Novel devices invented and researched in the context of nanoelectronics and quantum technologies exploit fundamentally different principles: they use quantum effects, and their behavior can hence not be explained by classical physics. Accordingly, such nanoscale devices need extremely low temperatures to operate. Also, in those systems, heating is hence detrimental to the performance and might even completely preclude the underlying quantum effects. Consequently, there is an essential need for controlling heat flows in nanoscale quantum devices. Simultaneously, quantum effects and size confinement also provide novel ways to control heat or implement heat engines with unprecedented functionalities.
This thesis deals with the theoretical study of heat control in nanoelectronic devices. We analyze in particular three effects that are unique to small-scale and quantum systems and propose to exploit them in concrete devices. First, due to quantum confinement, the conductance of nanoelectronic devices can have a strong energy dependence; this results in thermoelectric properties, which can be used for cooling. Second, phase coherence in quantum devices leads to opportunities to control heat flows coherently; based on this, heat valves and heat circulators can be designed. Finally, due to the absence of thermalization in small-scale devices, also the resources of engines can be non-thermal; this "non-thermal-ness" can be exploited as fuel for engines.
Areas of Advance
Nanoscience and Nanotechnology (SO 2010-2017, EI 2018-)
Condensed Matter Physics
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4876
Chalmers University of Technology
Kollektorn, MC2-huset, Kemivägen 9, Chalmers
Opponent: Dr María Rosa López Gonzalo, Universitat de les Illes Balears, Spain