Frontiers in Thermal Transport and Energy Conversion Proceedings of a Workshop (2020) / Chapter Skim
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3 Synthesis and Discussion
3 Synthesis and Discussion
Pages 29-34
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From page 29... ...
. Thermal Transport Vishwanath expressed his belief that thermal transport, specifically using the quantum Hall effect to probe non-Abelian quantum states, is the best means to probe exotic states of matter.
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From page 30... ...
A recent experiment was able to measure thermal Hall conductance, and the difference between the predicted integers and the resulting fractions showed some non-Abelian quantum Hall phases.4 Another experiment found non-Abelian quan tum Hall phases in the 5/2 state.5 Both experiments required very low temperatures, which added to their difficulty, but the results are part of the mounting, if indirect, evidence that this is either the Pfaffian state, which has these non-Abelian quasi 1 K von Klitzing, G
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From page 31... ...
The thermoelectric properties of composite fermions have been studied, but there are still many unanswered questions, and there is great potential to use their thermoelectric properties to probe exotic states of matter, Vishwanath said.6,7 Nodal semimetals, which have a zero density of states at a particular value of chemical potential, appear to have interesting thermoelectric properties, including for power generation and refrigeration, but alone they are unlikely to have good thermoelectric properties. However, if they are placed in a strong magnetic field, approaching the quantum limit, finite thermal power is possible.
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From page 32... ...
Ong noted that in the superconducting state, the thermal Hall effect comes from Bogoliubov quasiparticles, which are linear combinations of holes and elec trons. In a superconductor the thermal Hall effect arises from skew scattering of quasiparticles from vortices.
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From page 33... ...
Vishwanath noted that that is more chemical detail than physicists usually work with, although ab initio calculations of band structures are performed, but it is unclear how accurate the comparisons are. Heremans added that anharmonicity is also important, because the Born effective charge is critical to anharmonicity and shows up in thermal conductivity at high temperatures.
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From page 34... ...
Behnia agreed but added that they still work in most insulators, and Heremans noted that this measurement is under good control theoretically and experimentally. Vishwanath asked participants to share ideas for turning the fundamental aspects discussed, such as wave propagations and the nonlinear thermal transport coefficient, into technologies.
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