scholarly journals Subatomic mechanism of the oscillatory magnetoresistance in superconductors

2018 ◽  
Vol 64 (3) ◽  
pp. 261
Author(s):  
Boris I. Ivlev
Keyword(s):  
Magnetic Field ◽  
Spin Interaction ◽  
Cooper Pairs ◽  
Magnetic Field Direction ◽  
Bohr Radius ◽  
Material Parameters ◽  
Conduction Electrons ◽  
Angular Momenta ◽  
Spin Imbalance ◽  
Good Agreement

In the recent experiments [1] the unusual oscillatory magnetoresistance in superconductors was discovered with a periodicity essentially independent on magnetic field direction and even material parameters. The nearly universal period points to a subatomic mechanism of the phenomenon. This mechanism is related to formation inside samples of subatomically thin (10−11 cm) threads in the form of rings of approximately Bohr radius. Electron states of rings go over into conduction electrons which carry the same spin imbalance in energy as rings. The imbalance occurs due to spin interaction with the orbital momentum of the ring. The conductivity near Tc is determined by fluctuating Cooper pairs consisting of electrons with shifted energies. Due to different angular momenta of rings these energies periodically depend on magnetic field resulting in the observed oscillatory magnetoresistance. Calculated universal positions of peaks (n + 1/2)∆H (∆H \simeq 0.18T and n = 0, 1, 2...) on the R(H) curve are in a good agreement with measurements.

MAGNETORESISTANCE IN COPPER

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4434-4441
Author(s):  
SHIGEJI FUJITA ◽  
NEBI DEMEZ ◽  
JEONG-HYUK KIM ◽  
H. C. HO
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Kinetic Theory ◽  
Anisotropic Magnetoresistance ◽  
Magnetic Field Direction ◽  
Conduction Electrons ◽  
Fcc Lattice ◽  
A Charge ◽  
The Magnetic Field ◽  
Cyclotron Mass

The motion of the guiding center of magnetic circulation generates a charge transport. By applying kinetic theory to the guiding center motion, an expression for the magnetoconductivity σ is obtained: σ = e2ncτ/M*, where M* is the magnetotransport mass distinct from the cyclotron mass, nc the density of the conduction electrons, and τ the relaxation time. The density nc depends on the magnetic field direction relative to copper's fcc lattice, when Cu's Fermi surface is nonspherical with “necks”. The anisotropic magnetoresistance is analyzed based on a one-parameter model, and compared with experiments. A good fit is obtained.

Current Induced G-Factor Shift in Modulation Doped Si Quantum Wells

2006 ◽  
Vol 984 ◽  
Author(s):  
Hans Malissa ◽  
Wolfgang Jantsch ◽  
Friedrich Schäffler ◽  
Zbyslaw Wilamowski
Keyword(s):  
Magnetic Field ◽  
Quantum Wells ◽  
Electric Current ◽  
Magnetic Field Direction ◽  
G Factor ◽  
Conduction Electrons ◽  
Simple Effect ◽  
Spin Resonance ◽  
The Magnetic Field ◽  
A Current

AbstractWe report the observation of a particularly simple effect of spin-orbit coupling which allows for efficient manipulation of spins by an electric current in semiconductor nanostructures. Passing an electric current density of j = 2.5 mA/cm through a modulation doped Si quantum well (density of 5 × 1011 cm-2) perpendicular to an in-plane magnetic field, we observe a shift of the spin resonance of the conduction electrons (CESR) by about 0.1 mT. This shift reverses sign when we invert (i) the current direction, (ii) the magnetic field direction and it vanishes for perpendicular magnetic field. We show that this current-induced shift in g-factor, i.e., its dependence on current and carrier density, its temperature dependence and its anisotropy can be consistently and quantitatively explained in terms of the Bychkov-Rashba coefficient determined earlier from the CESR broadening and the g-factor anisotropy [1]. Other sources of magnetic field (e.g. the Oersted effect) are negligible. This effect can be utilized for g-factor tuning, and thus for local spin manipulation: passing a current through some part of a sample may be utilized to bring those electrons into resonance with a microwave field. These spins are thus excited to Rabi oscillations and, using current pulses of suitable duration, π rotations (or by any other angle) can be achieved.

Magnetoresistance investigation in the mixed state of a high temperature superconductor

2020 ◽  
Author(s):  
Mustapha Bghour ◽  
A. Labrag ◽  
H. El hamidi ◽  
A. Abou El hassan ◽  
A. Taoufik
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Mixed State ◽  
High Temperature Superconductor ◽  
Scaling Law ◽  
Good Alternative ◽  
Magnetic Field Direction ◽  
Flux Flow ◽  
The Magnetic Field ◽  
Good Agreement

In this work we analyze the behavior of magnetoresistance R(H,T) of a high temperature superconductor YBa2Cu3O7-delta thin film optimally doped. Measurements of magnetoresistance were carried out in the mixed state for a magnetic field up to 14T applied in the c-axis then parallel to ab-plane with a DC transport current of 100 and 500nA, 0.1 and 0.3mA perpendicular to the magnetic field direction in both cases. The obtained results show that the magnetoresistance is in a good agreement with the thermally assisted flux creep. However, the magnetoresistance in the flux flow regime cannot be described by the Barden-Stephen model which conjecture another origin of these results. In this sense, the quantum fluctuations of the order be parameter is a good alternative to understanding the shape of the magnetoresistance. The comparison of the magnetoresistance of the two directions shows that Rc(H,T) is larger than Rab(H,T) with anisot-ropy factor gamma=Rc/Rab depending on temperature and magnetic field. The irreversibility line Hirr(T) as well as Hc2(T) are determined and the first one is adjusted with the phenomenological model Hirr(T)=Hirr(0)(1-T/T0)^alpha where Hirr(0), T0 and alpha are parameters obtained from the fit. The investigation of the scaling law allows us to prove that a crossover from 3D to 2D behavior is a feature of our sample which justifies the existence of the decoherence effect.

SIMPLE MODEL FOR INTERFACE EXCITON WITH THE ELECTRON-HOLE SEPARATION IN A STRONG MAGNETIC FIELD

2000 ◽  
Vol 14 (25n26) ◽  
pp. 899-905 ◽  
Author(s):  
NGO VAN THANH ◽  
NGUYEN AI VIET
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Binding Energies ◽  
Oscillator Strengths ◽  
Bohr Radius ◽  
Electron Hole ◽  
Simple Theoretical Model ◽  
Magnetic Length ◽  
Junction Plane ◽  
Good Agreement

A simple theoretical model for the interface exciton in a strong magnetic field is studied, in which the electrons are confined in the junction plane and the local hole in the quantum well (δ doping3). The main parameter of this model is the separation d between electron and hole, which are assumed to be confined in the two planes. By variational numerical calculations, we obtain its main parameters: binding energies, effective Bohr radius and oscillator strengths, which depend strongly on the magnetic length. We find good agreement with previous results.

A 3 T superconducting magnet for long-run magnetic Compton-scattering experiments

1998 ◽  
Vol 5 (3) ◽  
pp. 937-939 ◽  
Author(s):  
Nobuhiko Sakai ◽  
Hiroshi Ohkubo ◽  
Yasushi Nakamura
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Compton Scattering ◽  
Superconducting Magnet ◽  
Field Direction ◽  
Compton Profile ◽  
Magnetic Field Direction ◽  
Long Run ◽  
Radiation Shields ◽  
The Magnetic Field

A 3 T superconducting magnet has been designed and constructed for magnetic Compton-profile (MCP) measurements with the new capabilities that the magnetic field direction can be altered quickly (within 5 s) and liquid-He refill is not required for more than one week. For the latter capability, two refrigerators have been directly attached to the cryostat to maintain the low temperature of the radiation shields and for the recondensation of liquid He. The system has been satisfactorily operated for over one week.

scholarly journals Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Evgeny D. Filippov ◽  
Sergey S. Makarov ◽  
Konstantin F. Burdonov ◽  
Weipeng Yao ◽  
Guilhem Revet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic ◽  
Radiative Properties ◽  
Magnetic Field Direction ◽  
Solid Target ◽  
Total Plasma ◽  
Plasma Confinement ◽  
X Ray ◽  
Magnetic Compression ◽  
The Magnetic Field

AbstractWe analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10$$^{12}$$ 12 –10$$^{13}$$ 13 W/cm$$^2$$ 2 ) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe that after $$\sim 8$$ ∼ 8  ns, the plasma is being overall shaped in a slab, with the plasma being compressed perpendicularly to the magnetic field, and being extended along the magnetic field direction. This dense slab rapidly expands into vacuum; however, it contains only $$\sim 2\%$$ ∼ 2 % of the total plasma. As a result of the higher density and increased heating of the plasma confined against the laser-irradiated solid target, there is a net enhancement of the total X-ray emissivity induced by the magnetization.

Effect of Magnetic Fields on the Resistance and Microstructure of Al-Cu Alloy during Solidification Processing

2011 ◽  
Vol 287-290 ◽  
pp. 2916-2920
Author(s):  
Chun Yan Ban ◽  
Peng Qian ◽  
Xu Zhang ◽  
Qi Xian Ba ◽  
Jian Zhong Cui
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Turning Points ◽  
Probe Method ◽  
Solidification Processing ◽  
Ac Magnetic Field ◽  
Dc Magnetic Field ◽  
Cu Alloy ◽  
The Difference ◽  
Good Agreement

The resistance of Al-21%Cu alloy under no magnetic field, DC magnetic field and AC magnetic field from liquid to solid was measured by a four-probe method. The difference of resistance versus temperature curves (R-T curves) was analyzed. It is found that the R-T curves of Al-21%Cu alloy are monotone decreasing and have two obvious turning points. Under DC magnetic field, the liquidus and solidus temperatures of the alloy both decrease, while under AC magnetic field, the liquidus and solidus temperatures both increase. There is a good agreement between the microstructure of quenching sample and R-T curves. The mechanism of the effect of magnetic fields was discussed.

Effects of repeated interactions and correlational disintegration on kinetic and transport properties of a non-neutral plasma in strong fields

1990 ◽  
Vol 44 (1) ◽  
pp. 167-190 ◽  
Author(s):  
Alf H. Øien
Keyword(s):  
Magnetic Field ◽  
Particle Transport ◽  
Axial Magnetic Field ◽  
Debye Length ◽  
Electron Plasma ◽  
Larmor Radius ◽  
Equilibration Time ◽  
Cylindrically Symmetric ◽  
Electric Potentials ◽  
Good Agreement

Collisions in a cylindrically symmetric non-neutral (electron) plasma, where the Larmor radius is much smaller than the Debye length, and the consequent particle transport, are studied. The plasma is confined radially by a strong axial magnetic field and axially by electric potentials. Hence two particles may interact repeatedly. Eventually they drift too far away from each other poloidally to interact any more, owing to shear in the E × B drift. The consequent build-up of correlation is limited by correlational disintegration due to collisions with ‘third particles’ between the repeated interactions. A kinetic equation including these effects is derived, and the cross-field particle transport along the density gradient is found. An associated equilibration time is shown to scale as B and to be in good agreement with the experimentally obtained values of Briscoli, Malmberg and Fine.

Doppler-Shifted Cyclotron Resonance in Thin Metal Films

1972 ◽  
Vol 50 (18) ◽  
pp. 2122-2137
Author(s):  
R. Turner ◽  
J. F. Cochran
Keyword(s):  
Magnetic Field ◽  
Metal Films ◽  
Thin Metal Film ◽  
Thin Metal ◽  
Free Electrons ◽  
Fermi Surfaces ◽  
First Order ◽  
Simple Quantum ◽  
The Magnetic Field ◽  
Good Agreement

According to Van Gelder the microwave absorption by a thin metal film in the presence of a static magnetic field normal to the film contains a series of peaks as the magnetic field is varied. In the present paper it is argued that these peaks correspond to Doppler-shifted cyclotron resonances of the carriers in the metal due to the quantization of electron momenta normal to the plane of the film. A simple quantum calculation is presented for the case of free electrons where the film is thin enough that to first order the microwave fields within are determined only by the boundary conditions and Maxwell's equations. The quantum expression is in good agreement with the absorption calculated using semiclassical arguments which can be readily extended to more complicated Fermi surfaces.

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