scholarly journals Electronic Contribution to the Thermal Diffusivity: DyBa2Cu3O7-y and Y0.9Ca0.1Ba2Cu3O7-z

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3087-3090 ◽  
Author(s):  
S. Dorbolo ◽  
H. Bougrine ◽  
M. Ausloos
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Band Structure ◽  
Order Parameter ◽  
Saddle Points ◽  
Three Dimensional ◽  
Electronic Contribution ◽  
Wave Symmetry ◽  
D Wave ◽  
Good Agreement

The electronic contribution to the specific heat and the thermal conductivity of high-T c superconductors is calculated with a three-dimensional band structure including saddle points and a Lawrence–Doniach coupling between the CuO2 planes. The electronic thermal diffusivity is deduced for s- and d-wave symmetry of the order parameter. Data on DyBa2Cu3O 7-y and Y0.9Ca0.1Ba2Cu3O 7-z and theory are in good agreement on the change of the slope near T c .

Thermal Diffusivity and Conductivity of La0.7Ca0.3-xSrxMnO3 (x=0 to 0.10)

2012 ◽  
Vol 501 ◽  
pp. 319-323
Author(s):  
Hasan A. Alwi ◽  
Lay S. Ewe ◽  
Zahari Ibrahim ◽  
Noor B. Ibrahim ◽  
Roslan Abd-Shukor
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Transition Temperature ◽  
Thermal Diffusivity ◽  
Electrical Properties ◽  
Room Temperature ◽  
Electronic Contribution ◽  
Insulator Metal Transition ◽  
Thermal And Electrical Properties

We report the room temperature thermal conductivity κ and thermal diffusivity α of polycrystalline La0.7Ca0.3-xSrxMnO3 for x = 0 to 0.1. The samples were prepared by heating at 1220 and 1320oC. The insulator-metal transition temperature, TIM and thermal diffusivity increased with Sr content. Phonon was the dominant contributor to thermal conductivity and the electronic contribution was less than 1%. Enhancement of electrical conductivity σ and thermal diffusivity for x ≥ 0.08 was observed in both series of samples. The grain size of the samples (28 to 46 µm) does not show any affect on the thermal and electrical properties.

scholarly journals A General Expression for the Stagnant Thermal Conductivity of Stochastic and Periodic Structures

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
X. Bai ◽  
C. Hasan ◽  
M. Mobedi ◽  
A. Nakayama
Keyword(s):  
Thermal Conductivity ◽  
General Expression ◽  
Metal Foam ◽  
Solid Angle ◽  
Periodic Structures ◽  
Three Dimensional ◽  
High Thermal Conductivity ◽  
Numerical Calculations ◽  
The One ◽  
Good Agreement

A general expression has been obtained to estimate thermal conductivities of both stochastic and periodic structures with high-solid thermal conductivity. An air layer partially occupied by slanted circular rods of high-thermal conductivity was considered to derive the general expression. The thermal conductivity based on this general expression was compared against that obtained from detailed three-dimensional numerical calculations. A good agreement between two sets of results substantiates the validity of the general expression for evaluating the stagnant thermal conductivity of the periodic structures. Subsequently, this expression was averaged over a hemispherical solid angle to estimate the stagnant thermal conductivity for stochastic structures such as a metal foam. The resulting expression was found identical to the one obtained by Hsu et al., Krishnan et al., and Yang and Nakayama. Thus, the general expression can be used for both stochastic and periodic structures.

DENSITY OF STATES AND ORDER PARAMETER IN DIRTY SUPERCONDUCTORS WITH A WEAKLY BROKEN d-WAVE SYMMETRY

1996 ◽  
Vol 10 (12) ◽  
pp. 537-544 ◽  
Author(s):  
SERGEI V. POKROVSKY
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Density Of States ◽  
Order Parameter ◽  
Zero Temperature ◽  
Scattering Rate ◽  
Wave Symmetry ◽  
Direct Calculations ◽  
D Wave ◽  
Gapless Superconductivity

It is shown by direct calculations that in a superconductor with a slightly violated d-wave symmetry of the order parameter (OP) the impurity driven phase transition from the gapless superconductivity to a state with a finite gap takes place at zero temperature. The corresponding scattering rate is close to the value at which the superconductivity vanishes in the d-superconductor. The behavior of the transition temperature, the OP and the density of states (DOS) is analyzed. The model is plausibly relevant to the BSCCO 2:2:1:2.

On the Origin of Zero-Bias Conductance Peak in High-Tc Superconductors

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3027-3030
Author(s):  
Alexander B. Nazarenko ◽  
Ernst A. Pashitskii ◽  
Alexander E. Pashitskii
Keyword(s):  
Elastic Scattering ◽  
Order Parameter ◽  
Magnetic Impurities ◽  
High Tc Superconductors ◽  
Zero Bias ◽  
High Tc ◽  
Conductance Peak ◽  
Wave Symmetry ◽  
Zero Bias Conductance ◽  
D Wave

We show that the zero-bias conductance peak observed in tunnel and point junctions of cuprates can be a consequence of "unitary" elastic scattering of the carriers by non-magnetic impurities in the vicinity of the junction interface and d-wave symmetry of the order parameter.

Pair Symmetry and Degree of Gap Depression at S-I Interfaces in HTS Josephson Junctions

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1301-1306
Author(s):  
G. A. Ummarino ◽  
R. S. Gonnelli ◽  
C. Bravi ◽  
Masumi Inoue
Keyword(s):  
Josephson Junctions ◽  
Order Parameter ◽  
Reference Value ◽  
High Tc Superconductors ◽  
S Wave ◽  
General Reference ◽  
High Tc ◽  
Wave Symmetry ◽  
Set Up ◽  
D Wave

A new possible indirect way of testing pair symmetry in high-Tc superconductors has been set up. The degree of intrinsic gap depression at Superconductor-Insulator [S-I] interfaces required to match Ic(T)Rn(T) data in HTS Josephson junctions depends on the pair symmetry of the material itself, so that an higher fraction of d-wave symmetry for the order parameter requires less gap depression, while an higher fraction of s-wave corresponds to a larger degree of gap depression. In order to obtain a general reference value for the intrinsic amount of gap depression at S-I interfaces the de Gennes condition has been used, and resulting reduced Ic(T)Rn(T) data have been calculated in the framework of a mixed (s+id)-wave pair symmetry for the depressed order parameter ranging from pure s to pure d-wave. This model has been tentatively applied to two junctions' made of very different HTSs: YBCO and BKBO, yielding a result of almost pure d-wave for YBCO and of pure s-wave for BKBO.

Phonon Thermal Conductivity of Superlattice Nanowires for Thermoelectric Applications

2003 ◽  
Vol 793 ◽  
Author(s):  
C. Dames ◽  
M. S. Dresselhaus ◽  
G. Chen
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Size Effects ◽  
Three Dimensional ◽  
Small Diameter ◽  
Particle Model ◽  
Phonon Thermal Conductivity ◽  
Alloy Scattering ◽  
Classical Size ◽  
Good Agreement

ABSTRACTAn incoherent particle model has been developed to predict the phonon thermal conductivity of nanowires and superlattice nanowires. It is argued that the surface roughness of most real nanowires prevents the formation of idealized confined dispersion relations for typical temperatures and diameters. Instead, the three-dimensional bulk dispersion is used, thus addressing only classical size effects. Four adjustable parameters capture the effects of diameter, superlattice, Umklapp, impurity, and alloy scattering. Predictions are compared with experimental data for nanowires and superlattice nanowires down to 22 nm diameter and 20 K, and are in good agreement above ∼40 nm diameter. The analysis suggests that ideal low thermal conductivity nanowires for thermoelectric applications would have small-diameter, alternating alloy segments that are acoustically dissimilar but electrically similar.

High-temperature superconductivity with d-wave symmetry of the order parameter (Review Article)

1998 ◽  
Vol 24 (11) ◽  
pp. 771-781 ◽  
Author(s):  
G. G. Sergeeva ◽  
Yu. P. Stepanovskiı̆ ◽  
A. V. Chechkin
Keyword(s):  
High Temperature ◽  
Order Parameter ◽  
High Temperature Superconductivity ◽  
Review Article ◽  
Wave Symmetry ◽  
D Wave

scholarly journals On the Jumps of Volume, Enthalpy and Entropy at the Melting Point, the Thermal Conductivity and Thermal Diffusivity for F.C.C. Au: the Temperature- and Pressure-Dependences

2021 ◽  
Vol 22 (4) ◽  
pp. 511-530
Author(s):  
Nguyen Quang  Hoc ◽  
Bui Duc  Tinh ◽  
Nguyen Duc  Hien ◽  
Le Hong  Viet
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Melting Point ◽  
Melting Curve ◽  
Debye Model ◽  
High Temperature And Pressure ◽  
Enthalpy And Entropy ◽  
Temperature And Pressure ◽  
Limiting Condition ◽  
Good Agreement

The melting temperature, the jumps of volume, enthalpy and entropy at the melting point, the isothermal compressibility, the thermal expansion coefficient, the heat capacity at constant volume, the Grüneisen parameter, the Debye temperature, the electrical resistivity, the thermal conductivity, and the thermal diffusivity for defective and perfect f.c.c. metals are studied by combining the statistical moment method (SMM), the limiting condition of the absolute stability of the crystalline state, the Clapeyron–Clausius equation, the Debye model, the Grüneisen equation, the Wiedemann–Franz law, and the Mott equation. Numerical calculations are carried out for Au under high temperature and pressure. The calculated melting curve of Au is in good agreement with experiments and other calculations. Obtained results are predictive and orient towards new experiments.

scholarly journals POINT CONTACT STUDY OF THE SUPERCONDUCTING ORDER PARAMETER IN RuSr2GdCu2O8

2005 ◽  
Vol 19 (01n03) ◽  
pp. 323-325 ◽  
Author(s):  
S. PIANO ◽  
F. BOBBA ◽  
F. GIUBILEO ◽  
A. M. CUCOLO ◽  
A. VECCHIONE
Keyword(s):  
Order Parameter ◽  
Magnetic Order ◽  
Point Contact ◽  
Superconducting Order Parameter ◽  
Zero Bias ◽  
Bulk Superconductivity ◽  
Conductance Peak ◽  
Wave Symmetry ◽  
Zero Bias Conductance ◽  
D Wave

We have performed a detailed study of the conductance characteristics obtained by point contact junctions realized between a normal Pt / Ir tip and syntered RuSr 2 GdCu 2 O 8 ( Ru -1212) samples. Indeed, this compound is subject of great interest due to the coexistence of both magnetic order and bulk superconductivity. In our experiments, the low temperature tunneling spectra reproducibly show a zero bias conductance peak that can be well reproduced by a generalized BTK model in the case of d-wave symmetry of the superconducting order parameter.

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