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Analogue viscous current flow near the onset of superconductivity
by Koushik Ganesan, Andrew Lucas
Submission summary
| Authors (as registered SciPost users): | Andrew Lucas |
| Submission information | |
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| Preprint Link: | https://arxiv.org/abs/2204.06567v4 (pdf) |
| Date submitted: | 2023-04-20 21:36 |
| Submitted by: | Lucas, Andrew |
| Submitted to: | SciPost Physics |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
Spatially resolved transport in two-dimensional quantum materials can reveal dynamics which is invisible in conventional bulk transport measurements. We predict striking patterns in spatially inhomogeneous transport just above the critical temperature in two-dimensional superconducting thin films, where electrical current will appear to flow as if it were a viscous fluid obeying the Navier-Stokes equations. Compared to viscous electron fluids in ultrapure metals such as graphene, this analogue viscous vortex fluid can exhibit a far more tunable crossover, as a function of temperature, from Ohmic to non-Ohmic transport, with the latter arising on increasingly large length scales close to the critical temperature. Experiments using nitrogen vacancy center magnetometry, or transport through patterned thin films, could reveal this analogue viscous flow in a wide variety of materials.
Author comments upon resubmission
(It would be nice if SciPost would add a button to attach PDF reply when resubmitting a manuscript :) ).
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Having read the authors' reply, my impression is that the effect predicted by this paper is very difficult to be observed experimentally. The expected correlation between width and conductivity is expected to occur in a a very narrow temperature range (less than Tc/100). This requires an unrealistically high level of homogeneity and sharpness of transition combined with a miraculous shutdown of other contributions to conductivity. Because of this irrelevance to actual experiments, I do not find that the paper qualifies for publication in Scipost Physics.
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I still do not understand the basic set-up that this paper is trying to discuss.
They use the pattern shown in Fig. 1. As I said earlier, I suspect that this would be cleaner to discuss theoretically for the Corbino geometry, where the fields and currents are rotationally symmetric about a central circle where the DC current is being injected (and flowing radially out to infinity).
I did not find a statement of what is meant by E^(0) in eqn. 2(b). A few lines above a "constant uniform transverse electric field" is mentioned, and looking at ref 12 it seems that this might be E^(0). As is mentioned in ref 12, this "external" field will induce some pattern of space charge in the (super)conducting film. If the material is a good superconductor close to its transition, the induced field should mostly cancel the background field within the film, making the field inside the superconductor much smaller, and concentrating the electric field within the barrier. But this is not what is said below eqn 2(b). Why would the induced field vanish anywhere? The space charge pattern will produce a field pattern given by Coulomb's law, and I do not see why or how that would vanish in any region.