scholarly journals Expansion of the high field-boosted superconductivity in UTe2 under pressure

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Sheng Ran ◽  
Shanta R. Saha ◽  
I-Lin Liu ◽  
David Graf ◽  
Johnpierre Paglione ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Field ◽  
Superconducting Phase ◽  
High Symmetry ◽  
First Order ◽  
Superconducting Phases ◽  
Quantum Phenomenon ◽  
Zero Resistance ◽  
Spin Triplet ◽  
The Magnetic Field

AbstractMagnetic field-induced superconductivity is a fascinating quantum phenomenon, whose origin is yet to be fully understood. The recently discovered spin-triplet superconductor, UTe2, exhibits two such superconducting phases, with the second one reentering in the magnetic field of 45 T and persisting up to 65 T. More surprisingly, in order to induce this superconducting phase, the magnetic field has to be applied in a special angle range, not along any high symmetry crystalline direction. Here we investigated the evolution of this high-field-induced superconducting phase under pressure. Two superconducting phases merge together under pressure, and the zero resistance persists up to 45 T, the field limit of the current study. We also reveal that the high-field-induced superconducting phase is completely decoupled from the first-order field-polarized phase transition, different from the previously known example of field-induced superconductivity in URhGe, indicating superconductivity boosted by a different paring mechanism.

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.

scholarly journals Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

2021 ◽  
Vol 7 (5) ◽  
pp. 60
Author(s):  
Luis M. Moreno-Ramírez ◽  
Victorino Franco
Keyword(s):  
Magnetic Field ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Second Order ◽  
Zero Field ◽  
First Order ◽  
Magnetic Field Change ◽  
Magnetocaloric Materials ◽  
Moderate Magnetic Field ◽  
The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

High magnetic field NMR investigation of the spin density wave phase of TMTSF2PF6

2002 ◽  
Vol 12 (9) ◽  
pp. 389-389
Author(s):  
W. G. Clark ◽  
F. Zamborsky ◽  
B. Alavi ◽  
P. Vonlanthen ◽  
W. Moulton ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Proton Relaxation ◽  
High Magnetic Fields ◽  
Organic Conductor ◽  
First Order ◽  
The Magnetic Field ◽  
Very High

We report proton NMR measurements of the effect of very high magnetic fields up to 44.7 T (1.9 GHz) on the spin density wave (SDW) transition of the organic conductor TMTSF2PF6. Up to 1.8 GHz, no effect of critical slowing close to the transition is seen on the proton relaxation rate (1/T1), which is determined by the SDW fluctuations associated with the phase transition at the NMR frequency. Thus, the correlation time for such fluctuations is less than $1O^{-10}$s. A possible explanation for the absence of longer correlation times is that the transition is weakly first order, so that the full critical divergence is never achieved. The measurements also show a dependence of the transition temperature on the orientation of the magnetic field and a quadratic dependence on its magnitude that agrees with earlier transport measurements at lower fields. The UCLA part of this work was supported by NSF Grant DMR-0072524.

STUDY OF PHASE PROPAGATION IN SUPERCONDUCTING ALUMINUM BY ULTRASONIC ATTENUATION MEASUREMENTS

1959 ◽  
Vol 37 (5) ◽  
pp. 614-618 ◽  
Author(s):  
K. L. Chopra ◽  
T. S. Hutchison
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Ultrasonic Attenuation ◽  
Cylindrical Specimen ◽  
Current Theory ◽  
Superconducting Phase ◽  
Rate Of Change ◽  
Time Rate ◽  
Phase Propagation ◽  
The Magnetic Field

The phase propagation in superconducting aluminum has been studied by measuring the time rate of change of ultrasonic attenuation. The time taken for the destruction of the superconducting phase in a cylindrical specimen, by means of a magnetic field, H, greater than the critical field, Hc, is approximately proportional to{H/(H–Hc)} in agreement with eddy-current theory. In the converse case, where the superconducting phase is restored by switching off the magnetic field H (>Hc), the total time taken is nearly independent of the temperature (or Hc) as well as H. The superconducting phase grows at a non-uniform volume rate which is considerably less than the uniform rate of collapse.

Abstract 14497: Mri Effects on Pacemaker/ICD Within the Magnetic Field; An Intra-observer Variability Study

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Robert W Biederman ◽  
Loretta Gevenosky ◽  
Geetha Rayarao ◽  
RONALD WILLIAMS ◽  
Richard Lombardi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Field ◽  
Meaningful Use ◽  
Observer Variability ◽  
Intrinsic Variability ◽  
Mri Scan ◽  
Clinical Routine ◽  
The Impact ◽  
Variability Study ◽  
The Magnetic Field

Introduction: The evolution of pacemaker/ICD safety in the magnetic field has triggered considerable interest in more clinical routine use. However, many limitations to widespread adoption of this seemingly implausible idea just a few years ago remain: unresolved impact of the high magnetic field, RF amplitude and oscillatory forces on electronics with possible high field damage to capacitor, solenoid and microcircuitry. However, given recent vender refinements over the last 10 years, we hypothesized that the impact on such circuitry may be far less than expected. Method: Consecutive interrogation of 940 pts who underwent clinically indicated MRI were evaluated over 5 years. This cohort was comprised of neuro/neurosurgical (72%), orthopedic (11%) and cardiac (17%) cases. Routine interrogation was performed within 10 min of entry into the bore of a dedicated Cardiac MRI (GE, 1.5T, WI). As well, reinterrogation was performed within 10 min of departure MRI (average 21±12min). At the time of interrogation pre and post MRI, a separate, repeat interrogation was performed within 5 min of each other such that 2 sets of PM/ICD parameters were obtained pre and post MRI. Result: No complications to either pt or device occurred during the MRI comprising 564 PMs and 376 ICDs. A cardiologist was present guiding the interrogation, configuration, and reconfiguration of the PM/ICD as well was present for entire MRI. There were no significant differences in common clinical parameters. More importantly, there was no difference in any parameter when compared in any order pre to post MRI scan. See Table. Conclusion: Intrinsic variability and inherent changes triggered by MRI environments are clinically insignificant and statistically negligible thereby removing yet another of the last remaining fears and apprehensions for primary PM/ICD failure and destruction as we move towards a more uniform acceptance of this technology for clinically meaningful use, dissemination and acceptance.

The interphase surface energy in some pure and impure superconductors

1960 ◽  
Vol 255 (1282) ◽  
pp. 407-426 ◽  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Surface Energy ◽  
Detailed Analysis ◽  
Energy Parameter ◽  
Transverse Magnetic ◽  
Superconducting Phase ◽  
Interphase Surface ◽  
Dilute Alloys ◽  
The Magnetic Field

A new method has been developed for obtaining relative values of the surface energy parameter, Δ, in superconductors. It involves the measurement of the resistance of thin films subjected to a transverse magnetic field. The method has been applied to tin, indium and aluminium and to dilute alloys of the first two. The principal new results are that Δ is 1⋅48 times larger in indium than in tin and that the addition of impurity to either metal lowers Δ without changing the nature of its temperature dependence. These conclusions are compared with current theories of the interphase surface energy. An attempt has been made to deduce the absolute magnitude of Δ, which requires a detailed analysis of the way in which the last traces of the superconducting phase are eliminated from the film by the action of the magnetic field. The analysis is necessarily over-simplified but it does give a figure for Δ in pure tin which is reasonably consistent with the previous estimates of Faber and Sharvin.

scholarly journals Low-degree mixed modes in red giant stars with moderate core magnetic fields

2019 ◽  
Author(s):  
Shyeh Tjing Loi ◽  
John C B Papaloizou
Keyword(s):  
Magnetic Field ◽  
Perturbation Theory ◽  
Magnetic Fields ◽  
Differential Equations ◽  
Order Perturbation ◽  
First Order ◽  
Low Degree ◽  
Mixed Modes ◽  
The Magnetic Field ◽  
First Order Perturbation

Abstract Observations of pressure-gravity mixed modes, combined with a theoretical framework for understanding mode formation, can yield a wealth of information about deep stellar interiors. In this paper, we seek to develop a formalism for treating the effects of deeply buried core magnetic fields on mixed modes in evolved stars, where the fields are moderate, i.e. not strong enough to disrupt wave propagation, but where they may be too strong for non-degenerate first-order perturbation theory to be applied. The magnetic field is incorporated in a way that avoids having to use this. Inclusion of the Lorentz force term is shown to yield a system of differential equations that allows for the magnetically-affected eigenfunctions to be computed from scratch, rather than following the approach of first-order perturbation theory. For sufficiently weak fields, coupling between different spherical harmonics can be neglected, allowing for reduction to a second-order system of ordinary differential equations akin to the usual oscillation equations that can be solved analogously. We derive expressions for (i) the mixed-mode quantisation condition in the presence of a field and (ii) the frequency shift associated with the magnetic field. In addition, for modes of low degree we uncover an extra offset term in the quantisation condition that is sensitive to properties of the evanescent zone. These expressions may be inverted to extract information about the stellar structure and magnetic field from observational data.

Conduction electron diamagnetism in alloys and magnetic-field-dependent dielectric constant of a Fermi gas

1964 ◽  
Vol 280 (1380) ◽  
pp. 85-96 ◽  
Keyword(s):  
Magnetic Field ◽  
Dielectric Constant ◽  
Free Electrons ◽  
Impurity Potential ◽  
First Order ◽  
Dilute Alloys ◽  
A Value ◽  
Field Dependent ◽  
Self Consistency ◽  
The Magnetic Field

The diamagnetism of free electrons in the presence of charged impurity centres which are sufficiently dilute to be non-interacting is calculated to first order in the strength of the potential of the impurity centre. This is done by combining the density-matrix treatment of Landau diamagnetism with the impurity-screening theory o f March & Murray. The susceptibility involves the integrated value of the impurity potential through the crystal, and its first derivative with respect to the magnetic field, B. If the impurity potential is assumed to have a value appropriate to B — 0, then the result for the change in diamagnetic susceptibility on alloying agrees with that of Kohn & Luming (1963). It is shown, however, that the impurity potential is modified in the presence of the magnetic field, and in particular it has angular dependence. The correction to the dia­magnetic susceptibility due to this self-consistency is shown to be significant (25% ). The relevance of the theory to experimental results on dilute alloys is briefly discussed. Finally, as a by-product of the investigation, we have obtained interesting results about the form of the field-dependent dielectric constant.

APPLYING THE 1/N APPROXIMATION TO THE DERIVATION OF THE BAND ENERGY OF THE HARPER EQUATION

2000 ◽  
Vol 14 (11) ◽  
pp. 373-376
Author(s):  
E. PAPP
Keyword(s):  
Magnetic Field ◽  
Reflection Symmetry ◽  
Band Energy ◽  
First Order ◽  
The Magnetic Field ◽  
Harper Equation

The 1/N approach to the Harper equation proposed previously is generalized towards performing the pertinent band-energy description. Leading forms and corrections proceeding to first order in the magnetic field are written down. The energy reflection symmetry has also been discussed.

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