Premonitory effects near critical transition temperature in ordering systems – a Monte Carlo simulation

2012 ◽  
Vol 92 (35) ◽  
pp. 4470-4483
Author(s):  
U.D. Kulkarni ◽  
A. Arya ◽  
S. Hata
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Transition Temperature ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
Ordering Systems

Correlation between oxygen excess density and critical transition temperature in superconducting Bi-2201, Bi-2212 and Bi-2223

2008 ◽  
Vol 63 (11-12) ◽  
pp. 1372-1375 ◽  
Author(s):  
H.P. Roeser ◽  
F. Hetfleisch ◽  
F.M. Huber ◽  
M.F. von Schoenermark ◽  
M. Stepper ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
Excess Density ◽  
Oxygen Excess

Reformulation of pairing theory

1988 ◽  
Vol 02 (05) ◽  
pp. 1101-1105 ◽  
Author(s):  
Miklos GULACSI ◽  
Zsolt GULACSI
Keyword(s):  
Transition Temperature ◽  
Size Effect ◽  
Layer Thickness ◽  
Short Communication ◽  
Cooper Pairing ◽  
Two Dimensional ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
Quantum Size ◽  
Natural Way

The original Cooper pairing theory is reformulated for electrons confined in a layer. This analysis is motivated by the quasi-two-dimensional character of the oxidic superconductors, in case of which the extension of the initial (3D) Cooper framework is practically impossible. By considering the electrons moving in a flat box, due to quantum size effect the properties of these oxidic superconductors can be explained in a natural way. In this short communication we will concentrate to the variation of the critical transition temperature due to the layer thickness and to the number of conduction (Cu-O) planes. The results are confirmed by the experiment. This being an evidence for the presence of the charge confinement effect in the oxidic superconductors.

The ferroelectric properties of Cd2Nb2O7: a Monte Carlo simulation study

2011 ◽  
Vol 44 (3) ◽  
pp. 585-594 ◽  
Author(s):  
T. Malcherek
Keyword(s):  
Phase Transition ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Transition Temperature ◽  
Soft Mode ◽  
Ferroelectric Properties ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Monte Carlo Simulation Study ◽  
First Order Phase Transition

The order–disorder contributions to the ferroelectric properties of Cd2Nb2O7(CNO) have been studied by Monte Carlo simulation of a 12-state modified Potts model on the pyrochlore lattice. Spin configurations obtained by these simulations are mapped to local Nb displacements. Secondary Cd displacements normal to the Nb displacement directions are considered as well. The model correctly reproduces diffuse scattering experimentally observed in CNO. A first-order phase transition is observed forkTp/J= 0.3891 (kis the Boltzmann constant,Tpis the model phase transition temperature andJis the interaction energy). To further adapt the model to the properties of CNO, coupling of local Nb displacements to theT2usoft mode is simulatedviathe addition of an appropriate field term in the model Hamiltonian. The critical temperatureTcof the soft mode is scaled tokTc/J= 0.3704. Similarities to experimental observations,i.e.the occurrence of stable domains with {100} boundaries, as well as spontaneous polarization along the cubic 〈100〉 and 〈110〉 directions, indicate thatTpcan be associated with the transition temperatureT1= 205 K in CNO. Frequency dispersion of the dielectric permittivity of CNO can be attributed to the low-frequency switching of correlated chains of Nb displacement that remain partially disordered in the temperature range between 195 and ∼100 K.

A link between critical transition temperature and the structure of superconducting

2008 ◽  
Vol 62 (12) ◽  
pp. 733-736 ◽  
Author(s):  
H.P. Roeser ◽  
F. Hetfleisch ◽  
F.M. Huber ◽  
M.F. von Schoenermark ◽  
M. Stepper ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Critical Transition ◽  
Critical Transition Temperature

BSCCO 2212 Defective Tellurium Ions on Bi-Site

2011 ◽  
Vol 319-320 ◽  
pp. 161-166 ◽  
Author(s):  
Morsy M.A. Sekkina ◽  
M. El-Hofy ◽  
Khaled M. Elsabawy ◽  
M. Bediwy
Keyword(s):  
Electrical Conductivity ◽  
Transition Temperature ◽  
Critical Transition ◽  
Chemical Formula ◽  
Hole Filling ◽  
Critical Transition Temperature ◽  
Solid State Reaction Technique ◽  
Conventional Solid State Reaction ◽  
Major Phase ◽  
Dc Electrical Conductivity

BSCCO 2212 superconducting samples, doped Tellurium, with the chemical formula Bi2-xTexSr2CaCu2O8, were prepared by the conventional solid state reaction technique. The prepared samples were studied utilizing XRD, DC-electrical conductivity and SEM. XRD spectra indicated that 2212 with tetragonal structure is the major phase, whereas Bi-2201 and CaTeO4 are minor phases. At higher Te-additions x, traces from some other semi conducting phases were detected. The critical transition temperature Tcoffset was found to decrease non-linearly with x, which attributed to the hole filling caused by the liberated electrons of Te4+ ions. For x–values in the range 0.1 ≤ x ≤ 0.4, the steepness of (ρ vs T) relationship increases abruptly around 150 K; this was attributed to change in the oxygen vacancy feature (phase-like transition). SEM photographs revealed that as Te-content increases the compactness of the surface and the connectivity of the grains decreases, while pores and voids increase as a result of decreasing the amount of Bi and presence of multiple-phases in the sample.

scholarly journals Gap Structure of the Overdoped Iron-Pnictide Superconductor Ba(Fe0.942Ni0.058)2As2: A Low-Temperature Specific-Heat Study

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
Gang Mu ◽  
Bo Gao ◽  
Xiaoming Xie ◽  
Yoichi Tanabe ◽  
Jingtao Xu ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Low Temperature ◽  
Specific Heat ◽  
Energy Gap ◽  
Critical Transition ◽  
Critical Transition Temperature ◽  
Iron Pnictide ◽  
Iron Pnictide Superconductor ◽  
Low Temperature Specific Heat ◽  
Co Doped

Low-temperature specific heat (SH) is measured on the postannealed Ba(Fe1−xNix)2As2single crystal withx= 0.058 under different magnetic fields. The sample locates on the overdoped sides and the critical transition temperatureTcis determined to be 14.8 K by both the magnetization and SH measurements. A simple and reliable analysis shows that, besides the phonon and normal electronic contributions, a clearT2term emerges in the low temperature SH data. Our observation is similar to that observed in the Co-doped system in our previous work and is consistent with the theoretical prediction for a superconductor with line nodes in the energy gap.

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