Non-uniqueness of the heat-current operator and the hopping thermoelectric and thermomagnetic phenomena

1973 ◽  
Vol 23 (10) ◽  
pp. 1050-1056 ◽  
Author(s):  
V. Čápek
Keyword(s):  
Heat Current ◽  
Current Operator ◽  
Thermomagnetic Phenomena

Entropy-based theory of thermomagnetic phenomena

2021 ◽  
pp. 2150190
Author(s):  
Andrei Sergeev ◽  
Michael Reizer
Keyword(s):  
Linear Response ◽  
Hot Spot ◽  
High Sensitivity ◽  
Transfer Entropy ◽  
Cooper Pairs ◽  
Heat Current ◽  
Electric And Magnetic Fields ◽  
Flux Formula ◽  
The Difference ◽  
Thermomagnetic Phenomena

We show that in the linear response approximation only entropy provides coupling between thermal and electric phenomena. The dissipationless quantum currents — magnetization, superconducting, persistent and topological edge currents — do not produce and transfer entropy and may be excluded from final formulas for thermomagnetic coefficients. The magnetization energy flux, [Formula: see text], in crossed electric and magnetic fields strongly modifies the Poynting vector in magnetic materials and metamaterials, but do not contribute to the heat current. Calculating entropy fluxes of fluctuating Cooper pairs in pure and disordered superconductors, we obtained the fluctuation Nernst coefficient proportional to [Formula: see text] ([Formula: see text] is the Fermi energy). We also introduce the thermomagnetic entropy per unit charge and derive the Nernst coefficient proportional to the difference of the thermoelectric and thermomagnetic entropies. This explains the Sondheimer cancellation and high sensitivity of thermomagnetic phenomena to correlations. In 2D superconductors, the transport entropy transferred by a vortex moving through the background formed by vortex–antivortex pairs is the configuration entropy of [Formula: see text], which strongly exceeds the intrinsic entropy of vortex core. Beyond the linear response, the nonentropic forces can lead to phenomena unexpected from thermodynamics, such as vortex attraction to the moving hot spot. Quantum currents do not transfer entropy and may be used as ideal connectors to quantum nanodetectors.

Onsager Relation and the Heat Current Operator in a System of Interacting Electrons and Phonons

1997 ◽  
Vol 257 (1) ◽  
pp. 44-64 ◽  
Author(s):  
Michael Reizer ◽  
Andrew Sergeev ◽  
John W. Wilkins ◽  
D.V. Livanov
Keyword(s):  
Heat Current ◽  
Current Operator ◽  
Onsager Relation ◽  
Interacting Electrons

A standardized modeling strategy for heat current method-based analysis and simulation of thermal systems

Energy ◽  
2021 ◽  
Vol 217 ◽  
pp. 119403
Author(s):  
Tian Zhao ◽  
Xi Chen ◽  
Ke-Lun He ◽  
Qun Chen
Keyword(s):  
Current Method ◽  
Heat Current ◽  
Thermal Systems ◽  
Modeling Strategy

scholarly journals Non-Linear Thermoelectric Devices with Surface-Disordered Nanowires

Applied Nano ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 162-183
Author(s):  
Peter Markoš ◽  
Khandker Muttalib
Keyword(s):  
Thermodynamic Parameters ◽  
Power Output ◽  
Heat Current ◽  
Linear Regime ◽  
Thermoelectric Devices ◽  
Charge Current ◽  
Thermal Current ◽  
Surface Disorder ◽  
Non Linear

We reviewed some recent ideas to improve the efficiency and power output of thermoelectric nano-devices. We focused on two essentially independent aspects: (i) increasing the charge current by taking advantage of an interplay between the material and the thermodynamic parameters, which is only available in the non-linear regime; and (ii) decreasing the heat current by using nanowires with surface disorder, which helps excite localized phonons at random positions that can strongly scatter the propagating phonons carrying the thermal current.

scholarly journals A Thermal Transport Study of Branched Carbon Nanotubes with Cross and T-Junctions

2021 ◽  
Vol 11 (13) ◽  
pp. 5933
Author(s):  
Wei-Jen Chen ◽  
I-Ling Chang
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Thermal Management ◽  
Thermal Transport ◽  
Topological Defects ◽  
Branch Length ◽  
Phonon Transport ◽  
Heat Current ◽  
Transport Mechanisms ◽  
Non Equilibrium Molecular Dynamics

This study investigated the thermal transport behaviors of branched carbon nanotubes (CNTs) with cross and T-junctions through non-equilibrium molecular dynamics (NEMD) simulations. A hot region was created at the end of one branch, whereas cold regions were created at the ends of all other branches. The effects on thermal flow due to branch length, topological defects at junctions, and temperature were studied. The NEMD simulations at room temperature indicated that heat transfer tended to move sideways rather than straight in branched CNTs with cross-junctions, despite all branches being identical in chirality and length. However, straight heat transfer was preferred in branched CNTs with T-junctions, irrespective of the atomic configuration of the junction. As branches became longer, the heat current inside approached the values obtained through conventional prediction based on diffusive thermal transport. Moreover, directional thermal transport behaviors became prominent at a low temperature (50 K), which implied that ballistic phonon transport contributed greatly to directional thermal transport. Finally, the collective atomic velocity cross-correlation spectra between branches were used to analyze phonon transport mechanisms for different junctions. Our findings deeply elucidate the thermal transport mechanisms of branched CNTs, which aid in thermal management applications.

scholarly journals Quantum control of excitons for reversible heat transfer

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Conor N. Murphy ◽  
Paul R. Eastham
Keyword(s):  
Heat Transfer ◽  
Quantum Dot ◽  
Quantum Control ◽  
Heat Engine ◽  
Laser Pulses ◽  
Heat Current ◽  
Light Emitting ◽  
Laser Dressing ◽  
Working Medium ◽  
Heat Transfers

Abstract Lasers, photovoltaics, and thermoelectrically-pumped light emitting diodes are thermodynamic machines which use excitons (electron-hole pairs) as the working medium. The heat transfers in such devices are highly irreversible, leading to low efficiencies. Here we predict that reversible heat transfers between a quantum-dot exciton and its phonon environment can be induced by laser pulses. We calculate the heat transfer when a quantum-dot exciton is driven by a chirped laser pulse. The reversibility of this heat transfer is quantified by the efficiency of a heat engine in which it forms the hot stroke, which we predict to reach 95% of the Carnot limit. This performance is achieved by using the time-dependent laser-dressing of the exciton to control the heat current and exciton temperature. We conclude that reversible heat transfers can be achieved in excitonic thermal machines, allowing substantial improvements in their efficiency.

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