Search results for "Meissner effect"
showing 8 items of 8 documents
Electromagnetic behaviour of superconductive amorphous metals
2005
The penetration depth of the magnetic field into an amorphous superconductor is calculated. The ratio of the London penetration depth δL to the electron free path le under zero temperature is above unity for almost all amorphous metals. That is why pure metals, in a superconducting state, change from type I superconductors to type II superconductors during the crystalline–amorphous transition.
Effect of a Locally Repulsive Interaction on s-wave Superconductors
2016
The thermodynamic impact of the Coulomb repulsion on s-wave superconductors is analyzed via a rigorous study of equilibrium and ground states of the strong coupling BCS-Hubbard Hamiltonian. We show that the one-site electron repulsion can favor superconductivity at fixed chemical potential by increasing the critical temperature and/or the Cooper pair condensate density. If the one-site repulsion is not too large, a first or a second order superconducting phase transition can appear at low temperatures. The Meißner effect is shown to be rather generic but coexistence of superconducting and ferromagnetic phases is also shown to be feasible, for instance, near half-filling and at strong repul…
Abelian dominance and the dual Meissner effect in local unitary gauges in SU(2) gluodynamics
2007
Performing highly precise Monte-Carlo simulations of SU(2) gluodynamics, we observe for the first time Abelian dominance in the confining part of the static potential in local unitary gauges such as the F12 gauge. We also study the flux-tube profile between the quark and antiquark in these local unitary gauges and find a clear signal of the dual Meissner effect. The Abelian electric field is found to be squeezed into a flux tube by the monopole supercurrent. This feature is the same as that observed in the non-local maximally Abelian gauge. These results suggest that the Abelian confinement scenario is gauge independent. Observing the important role of space-like monopoles in the Polyakov g…
Ferromagnetic gyroscopes for tests of fundamental physics
2020
A ferromagnetic gyroscope (FG) is a ferromagnet whose angular momentum is dominated by electron spin polarization and that will precess under the action of an external torque, such as that due to a magnetic field. Here we model and analyze FG dynamics and sensitivity, focusing on practical schemes for experimental realization. In the case of a freely floating FG, we model the transition from dynamics dominated by libration in relatively high externally applied magnetic fields, to those dominated by precession at relatively low applied fields. Measurement of the libration frequency enables in situ measurement of the magnetic field and a technique to reduce the field below the threshold for w…
Heat Capacity of Mesoscopic Superconducting Disks
1999
We study the heat capacity of isolated giant vortex states, which are good angular momentum ($L$) states, in a mesoscopic superconducting disk using the Ginzburg-Landau (GL) theory. At small magnetic fields the $L$=0 state qualitatively behaves like the bulk sample characterized by a discontinuity in heat capacity at $T_c$. As the field is increased the discontinuity slowly turns into a continuous change which is a finite size effect. The higher $L$ states show a continuous change in heat capacity at $T_c$ at all fields. We also show that for these higher $L$ states, the behavior of the peak position with change in field is related to the paramagnetic Meissner effect (irreversible) and can …
A novel paramagnetic molecular superconductor formed by bis(ethylenedithio)tetrathiafulvalene, tris(oxalato)ferrate(iii) anions and bromobenzene as g…
2005
The new paramagnetic molecular superconductor ET4[(H3O)Fe(C2O4)3]·C6H5Br (1) (Tc = 4.0 K) contains layers of superconducting ET donors alternating with paramagnetic hexagonal layers formed by (H3O)+, [Fe(C2O4)3]3− and guest C6H5Br molecules located in the hexagonal cavities. Conductivity measurements show metallic behavior from room temperature with a minimum in the resistivity at ca. 50 K followed by a smooth increase and a sharp drop in the resistivity with an onset at 4.0 K and a zero resistance at ca. 1.0 K. Magnetoresistance measurements indicate that Hc1 is about 7 mT and that Hc2 is very anisotropic (Hc2⊥ ≥ 5.5 T and Hc2|| ≈ 0.5 T). Magnetic susceptibility measurements show the expec…
Influence of magnetic field on cooling by normal-insulator–superconductor junctions
2000
Cooling by normal-insulator–superconductor junctions in external magnetic field has been studied experimentally. For all orientations of magnetic field the cooling performance correlates with the magnetic field dependent superconducting energy gap Δ(H). In perpendicular orientation of magnetic field with respect to the sample plane, additional degradation of the cooling power originates from scattering of nonequilibrium quasiparticles in the superconductor on magnetic vortices. The effect is hysteretic and its magnitude depends on the shape of the superconducting probes.
Gauge theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets
2017
We present the generalized quasiclassical theory of the long-range superconducting proximity effect in heterostructures with strong ferromagnets, where the exchange splitting is of the order of Fermi energy. In the ferromagnet the propagation of equal-spin Cooper pairs residing on the spin-split Fermi surfaces is shown to be governed by the spin-dependent Abelian gauge field which results either from the spin-orbital coupling or from the magnetic texture. This additional gauge field enters into the quasiclassical equations in superposition with the usual electromagnetic vector potential and results in the generation of spontaneous superconducting currents and phase shifts in various geometr…