Recent content by StanislavD

The math to the question is available in a paper https://arxiv.org/abs/1501.04978

Crystals may contain electronic real-space-eigenstates as ground states, which are spatially much larger than one unit cell, such as impurity states, standing waves at Brillouin zone edges, states of Anderson localization, etc. Every eigenstate is usually occupied by two conduction electrons...

This question is more complicated than it seems, most physicists cannot answer it unambiguously and there is no experiments to the issue. Imagine, a persistent supercurrent flows in a SC aluminum ring. Then we connect the SC aluminum ring (without solder) to an aluminum wire, the second end of...

If one single pair-breaking-event occurs once per second, then in a pair population the average life time is longer than one second.

An interesting paper in NATURE "A superconductor free of quasiparticles for seconds" https://www.nature.com/articles/s41567-021-01433-7 showing that superconducting (paired) electrons don't hop into normal states for seconds. The measurement device detects single pair-breaking-events for a large...

Exactly. The case j < j_c is very interesting. If j is independent of temperature, then the superfluid density is also independent and, thus, we can verify an important BSC prediction.

Imagine, in a mercury ring (superconductivity below Tc=4.15 K) we establish a persistent supercurrent. Then we organize temperature cycles (T-cycles) in the cryostat, from 3 K to 2.5 K and back. According to the BCS theory of superconductivity, the pair density decreases at warming, i.e. a not...

Unfortunately, it is not fun for me. Since years nobody could explain me the paradox of recombining pairs in the supercurrent. And few people recognize the issue as a real theoretical default of conventional theories; too uncomfortable situation for renowned institutions.

Another experiment. We vary T of mercury up/down, say from 3K to 2K and back. A supercurrent is excited before the first T-circle. According to BCS every T-circle destroys a not negligible fraction of pairs at warming, and creates the same fraction of pairs at cooling. The electromotive-force...

I agree, there is something to do and to improve in the story. Generally speaking, nanostructures may be a promising way to room temperature SC.

The weak reproducibility of results indicates, that the electronic structure of such nanostructures is very sensitive to fast degradation processes. So one cannot reproduce the result even in one the same sample. However, it does not deny the initial measurement results.

The solution is available. In BCS the supercurrent must somehow decrease because of thermal fluctuations (slowly or fast – depends on cryostat quality, however it is about microseconds, not about hours). In experiments – the supercurrent is constant for years, probably forever, independent of...

In the BCS theory the Cooper pair density depends on temperature, meaning that pairs can be created/annihilated by temperature variations. Obviously, momenta of annihilated pairs dissipate on the atom lattice, so an initial supercurrent dissipates. On the other hand, in some experiments a...

One important note about the superconductivity (SC) in the Ag/Au nanostructure: the result is perfectly in line with the SC approach of local electron pairing and Bose-Einstein-Condensation (BEC) of the pairs as bosons. In the indian paper the density of the Ag-clusters corresponds to the...