The quantum challenge on mesoscopic level

A. V. Nikulov

Home/Archive/arXiv

arXiv · 0707.4351

The quantum challenge on mesoscopic level

A. V. Nikulov

View original source ↗Read source document ↗Export metadata ↓

Abstract

Most experts reject the quantum potential introduced by David Bohm in 1952. But it is impossible to describe some quantum mesoscopic phenomena observed in superconductor nanostructures without a quantum force.

Explore related subjects

cond-mat.supr-con cond-mat.mes-hall

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

A. V. Nikulov. 2007-07-30. The quantum challenge on mesoscopic level. https://arxiv.org/abs/0707.4351

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Superheating field of clean superconductors near the type-I--type-II boundary: the low-temperature Meissner stability limit of niobium

We calculate the low-temperature superheating field $B_{\rm sh}$ of clean superconductors near the boundary between type-I and type-II superconductivity, with particular emphasis on Nb. Ginzburg--Landau theory is not applicable at low temperatures, while previous microscopic calculations have been limited to either the large-$κ$ regime or the dirty limit. The clean, low-$κ$ regime relevant to Nb has therefore remained unresolved. We solve the self-consistent nonlinear nonlocal Eilenberger problem for the Meissner state and then analyze its stability against small perturbations. For a Nb-like material with $κ_{\rm GL}=0.7$, we obtain $B_{\rm sh}\simeq 290\,{\rm mT}$ at $T/T_c=0.2$, using $B_{c0}\simeq 200\,{\rm mT}$. For a TESLA-shaped Nb accelerator cavity, this corresponds to an intrinsic Meissner-stability limit of about $67\,{\rm MV/m}$.

cond-mat.supr-con↗

arXiv2026

Field-free superconducting diode and tunable vortex dynamics in NbN/FePt stripe-domain heterostructures

We demonstrate reconfigurable, field-free superconducting diode behavior in NbN/FePt and NbN/AlN/FePt heterostructures with remanent stripe domains in the FePt layer. NbN films 10 nm thick are capped either directly with FePt or through a thin AlN spacer, which reduces electronic proximity effects while preserving magnetic coupling through stray fields. At zero applied magnetic field, the superconducting diode efficiency reaches approximately 50--60% in NbN/FePt when the stripes are perpendicular to the current and is strongly reduced when they are parallel. The diode effect persists in NbN/AlN/FePt with efficiencies reaching approximately 35--40%, supporting a magnetic origin of the nonreciprocity. We interpret the response as asymmetric vortex transport in the remanent magnetic landscape, with preferential edge vorticity and a Lorentz force that favors inward flux injection or outward motion depending on current polarity. Under applied perpendicular magnetic fields, the interplay between the external field and the magnetic stray fields modifies the flux-flow instability and the apparent instability velocity inferred from transport, with values below those reported for bare NbN films. These results show that stripe-domain ferromagnetic overlayers provide a reconfigurable route to control superconducting nonreciprocity and flux-flow stability in NbN-based heterostructures.

cond-mat.supr-con↗

arXiv2026

Cluster property and entanglement in the superconducting state

We present the conditions for satisfying the cluster property in the superconducting state. Using these conditions, we show that the cluster property employed when deriving the order parameter of the superconducting state (OPSS) holds true, and that the OPSS is given by ${}_S\langle Ψ| \hatψ(x)\hatψ(x') | Ψ\rangle_S$, where $|Ψ\rangle_S$ is the superconducting state, and where $\hatψ(x)$ is the field operator of superconducting electrons. This provides a resolution to the long-standing concern raised by Leggett et al.\ regarding particle-number fluctuation in the superconducting state. In addition, by considering the entanglement between two particles composed of the maximum geminal of the BCS ground state [J.\ Phys. Commun. 5, 095003 (2021)], it is confirmed that the larger the deviation from the conditions for satisfying the cluster property becomes, the greater the magnitude of the entanglement becomes. This shows not only the effectiveness of the conditions for satisfying the cluster property but also the justification of the OPSS that has been commonly used.

cond-mat.supr-con↗