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arXiv:1906.09191 · Physical Review Research

Bosonic superfluid transport in a quantum point contact

Shun Uchino, Jean-Philippe Brantut

Published Jun 4, 2020• 16 citations
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Abstract

This paper presents a microscopic theory of heat and particle transport in a bosonic superfluid point contact. The authors find features different from traditional, fermionic superconductors, such as Ohm's law obeyed in DC transport and odd-order harmonics in AC transport, as well as breakdown of the Wiedemann-Franz law.
DOI
10.1103/physrevresearch.2.023284

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Department of Physics, Harvard University, Cambridge, MA 02138(Dated: Printed February 2, 2008)We study electric, thermal, and thermoelectric conductivities in the vicinity of a z = 2superconductor-diffusive metal transition in two dimensions, both in the high and low frequencylimits. We find violation of the Wiedemann-Franz law and a dc thermoelectric conductivity α thatdoes not vanish at low temperatures, in contrast to Fermi liquids. We introduce a Langevin equationformalism to study critical dynamics over a broad region surrounding the quantum critical point.INTRODUCTION

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We theoretically investigate the thermal-transport properties of a unitary Fermi gas between two reservoirs connected by a quantum point contact. We find several distinguished properties that are qualitatively different from those of weak or noninteracting gas systems. The particle transport figure of merit is drastically enhanced in the unitary regime. The Lorentz number violates the Wiedemann-Franz law, demonstrating the breakdown of Fermi liquid. These transport properties are the hallmarks of the unitary Fermi gas and are attributed to the existence of preformed Cooper pairs. The variation of the thermal-transport coefficients due to the changing of the transmission coefficient is also studied.
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We study electric, thermal, and thermoelectric conductivities in the vicinity of a z=2z=2z=2 superconductor-diffusive metal transition in two dimensions, both in the high- and low-frequency limits. We find violation of the Wiedemann-Franz law and a dc thermoelectric conductivity $\ensuremath{\alpha}$ that does not vanish at low temperatures, in contrast to Fermi liquids. We introduce a Langevin equation formalism to study critical dynamics over a broad region surrounding the quantum critical point.
Department of Physics, Harvard University, Cambridge, MA 02138(Dated: Printed February 2, 2008)We study electric, thermal, and thermoelectric conductivities in the vicinity of a z = 2superconductor-diffusive metal transition in two dimensions, both in the high and low frequencylimits. We find violation of the Wiedemann-Franz law and a dc thermoelectric conductivity α thatdoes not vanish at low temperatures, in contrast to Fermi liquids. We introduce a Langevin equationformalism to study critical dynamics over a broad region surrounding the quantum critical point.INTRODUCTION