Thermopower oscillations in mesoscopic Andreev interferometers

Titov, M.

doi:10.1103/physrevb.78.224521

Cited by 36 publications

(65 citation statements)

References 35 publications

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“…A period of 2π had also been found previously in Ref. 40. The antisymmetry and the periodicity may also be obtained by (39a) and (39b) combined with (19) and (36a) Thus, replacing φ with −φ is the same as replacing with − .…”

Section: B Asymmetric Housesupporting

confidence: 68%

Conductance and thermopower of ballistic Andreev cavities

2011

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When coupling a superconductor to a normal conducting region the physical properties of the system are highly affected by the superconductor. We investigate the effect of one or two superconductors on the conductance of a ballistic chaotic quantum dot to leading order in the total channel number using trajectory-based semiclassics. The results show that the effect of one superconductor on the conductance is of the order of the number of channels and that the sign of the quantum correction from the Drude conductance depends on the particular ratios of the numbers of channels of the superconducting and normal conducting leads. In the case of two superconductors with the same chemical potential, we additionally study how the conductance and the sign of quantum corrections are affected by their phase difference. As far as random matrix theory results exist these are reproduced by our calculations. Furthermore, in the case that the chemical potential of the superconductors is the same as that of one of the two normal leads the conductance shows, under certain conditions, similar effects as a normal metal-superconductor junction. The semiclassical framework is also able to treat the thermopower of chaotic Andreev billiards consisting of one chaotic dot, two normal leads, and two superconducting islands and shows it to be antisymmetric in the phase difference of the superconductors.

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Section: B Asymmetric Housesupporting

confidence: 68%

Conductance and thermopower of ballistic Andreev cavities

2011

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“…It would be a good idea to do theory for cases when (N SC1 + N SC2 ) is of order (N L + N R ), as ZT should be much larger there. For that one would have to treat the difficult problem of multiple scattering from the superconductor; this could be done by treating the scatterer as a random matrix [158], or by switching to the Usadel approach [236][237][238][239][240]. However, we are not aware of any works that explore how to maximize ZT in such systems.…”

Section: Thermopower As Odd-function Of External Magnetic-fieldmentioning

confidence: 99%

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

et al. 2017

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In recent years, the study of heat to work conversion has been re-invigorated by nanotechnology. Steady-state devices do this conversion without any macroscopic moving parts, through steady-state flows of microscopic particles such as electrons, photons, phonons, etc. This review aims to introduce some of the theories used to describe these steady-state flows in a variety of mesoscopic or nanoscale systems. These theories are introduced in the context of idealized machines which convert heat into electrical power (heat-engines) or convert electrical power into a heat flow (refrigerators). In this sense, the machines could be categorized as thermoelectrics, although this should be understood to include photovoltaics when the heat source is the sun. As quantum mechanics is important for most such machines, they fall into the field of quantum thermodynamics. In many cases, the machines we consider have few degrees of freedom, however the reservoirs of heat and work that they interact with are assumed to be macroscopic. This review discusses different theories which can take into account different aspects of mesoscopic and nanoscale physics, such as coherent quantum transport, magnetic-field induced effects (including topological ones such as the quantum Hall effect), and single electron charging effects. It discusses the efficiency of thermoelectric conversion, and the thermoelectric figure of merit. More specifically, the theories presented are (i) linear response theory with or without magnetic fields, (ii) Landauer scattering theory in the linear response regime and far from equilibrium, (iii) Green-Kubo formula for strongly interacting systems within the linear response regime, (iv) rate equation analysis for small quantum machines with or without interaction effects, (v) stochastic thermodynamic for fluctuating small systems. In all cases, we place particular emphasis on the fundamental questions about the bounds on ideal machines. Can magnetic-fields change the bounds on power or efficiency? What is the relationship between quantum theories of transport and the laws of thermodynamics? Does quantum mechanics place fundamental bounds on heat to work conversion which are absent in the thermodynamics of classical systems?

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“…Here the effect is essentially related to the temperature dependence of the supercurrent. Later this effect was considered further in mesoscopic Andreev interferometers [20][21][22][23][24] and used to explain partially the experimental findings [9].During the last decade superconductor-ferromagnet heterostructures have attracted a considerable interest. Driven by the prospect to create, among other perspectives, unconventional triplet pairing [25][26][27][28][29][30], superconducting spin-valves [31,32] or to study spin-polarized Andreev reflection [33][34][35][36][37], many aspects of superconductor-ferromagnet heterostructures have been investigated theoretically [38][39][40][41][42][43][44] and experimentally [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61].…”

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confidence: 99%

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confidence: 99%

Giant thermoelectric effects in a proximity-coupled superconductor–ferromagnet device

2014

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The usually negligibly small thermoelectric effects in superconducting heterostructures can be boosted dramatically due to the simultaneous effect of spin splitting and spin filtering. Building on an idea of our earlier work (Machon et al 2013 Phys. Rev. Lett. 110 047002), we propose realistic mesoscopic setups to observe thermoelectric effects in superconductor heterostructures with ferromagnetic interfaces or terminals. We focus on the Seebeck effect being a direct measure of the local thermoelectric response and find that a thermopower of the order of ∼250 μ − V K 1 can be achieved in a transistor-like structure. A measurement of the thermopower can furthermore be used to determine quantitatively the spin-dependent interface parameters that induce the spin splitting. For applications in nanoscale cooling we discuss the figure of merit for which we find values exceeding 1.5 for temperatures ≲1 K.Keywords: thermopower, figure of merit, proximity effect, quasiclassical theory, spin-dependent boundary conditionsSince their discovery at the beginning of the 19th century [1-4], thermoelectric effects have attracted continued attention in physics, as they provide the basis for a large variety of devices used in a multitude of fields in physics and engineering connected with energy management and harvesting. The coupling of thermal and electric transport equations is also a basic concept in (k B is the Boltzmann constant and T the temperature) around the chemical potential. As consequence, in standard metals, described by Fermi-liquid theory, thermoelectric effects are strongly suppressed at temperatures well below the Fermi temperature, since the single-particle DOS and the scattering rates vary on a much larger energy scale than k T B . We note that, in contrast, in nanoscale conductors even in the simple Landauer picture of free electrons the transmission function may depend considerably on energy, e.g. in quantum dots or due to interaction effects, and can lead to a sizable thermoelectric effect [14][15][16]. The same holds for strongly correlated metals with a strong variation of the DOS at the Fermi level and for semiconductors with a Fermi level near the bottom or top of an energy band.However, with regard to thermoelectric effects in superconductors the situation is less favorable. The most widely used Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity [17] is essentially build on top of a deeply degenerate Fermi gas. This is reflected in the almost perfect electron-hole symmetry in the standard version of the theory, appropriate for conventional low-temperature superconductors, suppressing thermoelectric effects [18,19]. On the other hand, supercurrents can interfere with thermal currents and generate a thermoelectric voltage in interferometer geometries [18]. Here the effect is essentially related to the temperature dependence of the supercurrent. Later this effect was considered further in mesoscopic Andreev interferometers [20][21][22][23][24] and used to explain partially the experimental finding...

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Thermopower oscillations in mesoscopic Andreev interferometers

Cited by 36 publications

References 35 publications

Conductance and thermopower of ballistic Andreev cavities

Conductance and thermopower of ballistic Andreev cavities

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Giant thermoelectric effects in a proximity-coupled superconductor–ferromagnet device

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