Abstract
We present a microscopic theory of heat and particle transport of an interacting, low temperature Bose-Einstein condensate in a quantum point contact. We show that, in contrast to charged, fermionic superconductors, bosonic systems feature tunneling processes of condensate elements, leading to the presence of odd-order harmonics in the AC Josephson current. A crucial role is played by an anomalous tunneling process where condensate elements are coherently converted into phonon excitations, leading to even-order harmonics in the AC currents as well as a DC contribution. At low bias, we find dissipative components obeying Ohm's law, and bias-independent nondissipative components, in sharp contrast to fermionic superconductors. Analyzing the DC contribution, we find zero thermopower and Lorenz number at zero temperature, a breakdown of the bosonic Wiedemann-Franz law. These results highlight importance of the anomalous tunneling process inherent to charge neutral superfluids. The consequences could readily be observed in existing cold-atom transport setups.
Highlights
A mesoscopic system connected to reservoirs is one of the most important examples of nonequilibrium quantum statistical physics [1]
We describe the channel as a single-mode quantum point contacts (QPCs), which is adequate when its width and length are much shorter than the coherence length of the Bose-Einstein condensate (BEC)
We consider the situation in which the chemical potential in the reservoirs is fixed, which is standard in the condensed-matter physics context
Summary
A mesoscopic system connected to reservoirs is one of the most important examples of nonequilibrium quantum statistical physics [1]. QPCs are the cornerstone of mesoscopic quantum devices, as building blocks for quantum coherent devices such as quantum dots and interferometers Their counterparts in atomic gases open the perspective of complex, quantum coherent ’atom-tronic’ devices [8,9,10,11] featuring controlled interactions [12] and the possibility of using fermionic or bosonic statistics [13,14,15]. In the superfluid phase, there always exist gapless collective modes which are not present in charged systems due to the AndersonHiggs mechanism [16,17]. We present a microscopic theory of lowtemperature transport of interacting neutral bosons through a single-mode QPC. In Appendixes A and B, some technical details on the theoretical analyses are provided
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
