Some Effects of Pressure on Superconductivity

We have calculated the effect of hydrostatic pressure on select properties of a number of simple superconducting metals. We discuss the changes with decreasing volume in the critical temperature, the zero temperature gap, the condensation energy, and the normal state specific heat. Semiquantitative agreement with experiment is obtained in all cases. Throughout, the Eliashberg formulation is employed. Information on the kernels entering into these equations is taken from quasi particle tunneling data at zero pressure. At finite pressure the kernels are rescaled according to a simple model.

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Pressure effect on the electrical resistance of Y0.77Pr0.23Ba2Cu3O7-δ single crystals

The Journal of V. N. Karazin Kharkiv National University, Series "Physics" ◽

10.26565/2222-5617-2020-33-05 ◽

2020 ◽

Keyword(s):

Critical Temperature ◽

Hydrostatic Pressure ◽

Single Crystals ◽

Electrical Resistance ◽

Simultaneous Increase ◽

Critical Temperatures ◽

Electron Phonon Interaction ◽

The Matrix ◽

Critical Temperature Tc ◽

Effect Of Hydrostatic Pressure

The effect of hydrostatic pressure up to 12 kbar on the electrical resistance in the basal ab-plane of optimally oxygen-doped (δ<0.1) single crystals Y1–xPrxBa2Cu3O7–δ moderately doped with praseodymium (x≈0.23) with a critical temperature Tc≈67 K. Compared to undoped single-crystal YBa2Cu3O7–δ, doping with praseodymium led to a decrease in the critical temperature by ≈24 K with a simultaneous increase in ρab (300 K) by ≈130 μΩcm. In the region of the transition to the superconducting state, several clearly pronounced peaks are observed on the dρ/dT – T curves, which indicates the presence of several phases with different critical temperatures in the sample. The application of high hydrostatic pressure leads to an increase in Tc by about 3 K. This increase slows down with increasing pressure, and the baric derivatives, dTc/dP, decrease from 0.44 K/kbar at atmospheric pressure to 0.14 K/kbar at 11 kbar. The comparatively weak change in the critical temperature under the action of hydrostatic pressure is due to the relatively small value of the orthorhombic distortion, (a–b)/a. The change in the baric derivative dTc/dP upon all-round compression of the sample is due to the fact that, along with an increase in the Debye temperature, the matrix element of the electron-phonon interaction also increases. Possible mechanisms of the effect of high pressure on Tc are discussed taking into account the presence of features in the electronic spectrum of carriers.

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Peculiarities of pseudogap in Y0.95Pr0.05Ba2Cu3O7−δ single crystals under pressure up to 1.7 GPa

Scientific Reports ◽

10.1038/s41598-019-55959-1 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 7

Author(s):

A. L. Solovjov ◽

L. V. Omelchenko ◽

E. V. Petrenko ◽

R. V. Vovk ◽

V. V. Khotkevych ◽

...

Keyword(s):

Critical Temperature ◽

Hydrostatic Pressure ◽

Single Crystal ◽

Single Crystals ◽

Temperature Interval ◽

Fluctuation Theory ◽

Structural Defects ◽

Fluctuation Conductivity ◽

First Time ◽

Effect Of Hydrostatic Pressure

AbstractThe effect of hydrostatic pressure up to P = 1.7 GPa on the fluctuation conductivity σ′(T) and pseudogap ∆*(T) in Y0.95Pr0.05Ba2Cu3O7−δ single crystal with critical temperature Тс = 85.2 K (at P = 0) was investigated. The application of pressure leads to the increase in Tc with dTc/dP = +1.82 K∙GPa−1 while the resistance decreases as dlnρ(100 K)/dP = −(10.5 ± 0.2) %∙GPa−1. Regardless of the pressure, in the temperature interval from Tc to T0 (~88 K at P = 0) the behaviour of σ′(T) is well described by the Aslamazov – Larkin (AL – 3D) fluctuation theory, and above the T0 by the Lawrence – Doniach theory (LD). The Maki-Thompson (MT – 2D) fluctuation contribution is not observed. This indicates the presence of structural defects in the sample induced by Pr. Here it is determined for the first time that when the pressure is applied to the Y1−xPrxBa2Cu3O7−δ single crystal, the pseudogap increases as dlnΔ*/dP = 0.17 GPa–1.

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CONDENSATION STATE OF ULTRA-COLD BOSE ATOMIC GASES WITH NONCONTACT INTERACTION

International Journal of Modern Physics B ◽

10.1142/s0217979213610079 ◽

2013 ◽

Vol 27 (07) ◽

pp. 1361007

Author(s):

ZE CHENG

Keyword(s):

Critical Temperature ◽

Negative Energy ◽

Atomic Gases ◽

Zero Temperature ◽

Normal Fluid ◽

Quasi Particle ◽

First Order Phase Transition ◽

Opposite Wave ◽

First Order Phase ◽

Atom System

Within the framework of quantum field theory, we find that uniform Bose atomic gases with noncontact interaction can undergo a Bardeen–Cooper–Schrieffer (BCS) condensation below a critical temperature. In the BCS condensation state, bare atoms with opposite wave vectors are bound into pairs, and unpaired bare atoms are transformed into a new kind of quasi-particle, i.e., the dressed atom. The atom-pair system is a condensate or a superfluid and the dressed-atom system is a normal fluid. At absolute zero temperature the condensate possesses a lowest negative energy. The critical temperature and the effective mass of dressed atoms are derived analytically. The transition from the BCS condensation state to the normal state is a first-order phase transition.

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Effect of hydrostatic pressure on the resistance and critical temperature of YBa2Cu3O7−δ single crystals

Low Temperature Physics ◽

10.1063/1.593445 ◽

1997 ◽

Vol 23 (10) ◽

pp. 777-781 ◽

Cited By ~ 40

Author(s):

D. D. Balla ◽

A. V. Bondarenko ◽

R. V. Vovk ◽

M. A. Obolenskii ◽

A. A. Prodan

Keyword(s):

Critical Temperature ◽

Hydrostatic Pressure ◽

Single Crystals ◽

Effect Of Hydrostatic Pressure

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TRANSPORT PROPERTIES OF ANYONS

International Journal of Modern Physics B ◽

10.1142/s0217979292002267 ◽

1992 ◽

Vol 06 (17) ◽

pp. 2837-2854

Author(s):

D. V. KHVESHCHENKO

Keyword(s):

Phase Transition ◽

Critical Temperature ◽

Transport Properties ◽

Stress Tensor ◽

Electric Current ◽

Normal State ◽

Correlation Functions ◽

Electromagnetic Response ◽

Zero Temperature ◽

Tensor Correlation

We consider electromagnetic response as well as electrical and thermal transport in a normal state of anyon system at finite temperatures. We find the frequency and momentum dependences of electrical and thermal conductivities in the longwavelength limit. It is also shown that a pole of electric current and stress tensor correlation functions identified at zero temperature with a gapless sound-like mode becomes a diffusion above the critical temperature of the hypothetical superfluid anyon phase transition.

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Contribution to the Theory of Weak Coupling Superconductors

Canadian Journal of Physics ◽

10.1139/p71-088 ◽

1971 ◽

Vol 49 (6) ◽

pp. 724-746 ◽

Cited By ~ 48

Author(s):

C. R. Leavens ◽

J. P. Carbotte

Keyword(s):

Critical Temperature ◽

Isotope Effect ◽

Normal State ◽

Weak Coupling ◽

Analytic Solution ◽

Numerical Solutions ◽

Approximate Analytic Solution ◽

Zero Temperature ◽

Eliashberg Equations ◽

Normal State Properties

We have managed to simplify the Eliashberg equations for the case of weak coupling superconductors. Further, an explicit approximate analytic solution of the simplified equations has been obtained for the zero temperature gap edge. An expression for the critical temperature is also given. It is found to be of the BCS form and allows the BCS parameter N(0)V to be identified with a simple function of the normal state properties. The validity of our simplified integral equations and of our analytic solution is established by comparison with numerical solutions of the complete Eliashberg equations. The equations are used to discuss the effect of pressure on the gap, the isotope effect, as well as other properties.

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