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Wyświetlanie 1-12 z 12
Tytuł:
Conditions for the Cooper Pair Creation in 2- up to 3-Dimensional Fermi Liquids
Autorzy:
Gonczarek, R.
Mulak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1931808.pdf
Data publikacji:
1994-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
67.50.Fi
Opis:
We reconsider the Pfitzner and Wölfle results concerning the quasi-particle scattering amplitude in Fermi liquid and adopt them to the sufficiently low-temperature and flat-confined systems, where solely two types of quasi--particle interactions are permitted. We find relations between the pairing interaction and Landau parameters and establish plain criteria for the creation of singlet or triplet Cooper pairs. Moreover, we present methods allowing us to estimate values of interaction parameters and transition temperatures in flat-confined systems basing on their bulk parameters. The obtained results are in agreement with experimental data for helium-3 and its films and explain an absence of superconductivity in alkali metals.
Źródło:
Acta Physica Polonica A; 1994, 86, 6; 929-938
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Parametric Equations for the Energy Gap. Extended BCS Case
Autorzy:
Gonczarek, R.
Mulak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1931831.pdf
Data publikacji:
1994-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
Opis:
The generalised form of the gap equation which comprises also some non-BCS approaches is defined and solved. The parametric gap equations have been derived in a few equivalent cases and discussed in$\text{}_{}$dissimilar limits. It is shown that the relations between the critical temperature and zero-temperature energy gap can be extended for all systems under consideration. The main benefits and incontestable advantage of the presented method are demonstrated with regard to the general BCS case.
Źródło:
Acta Physica Polonica A; 1994, 86, 6; 1007-1014
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Discontinuous Phase Transitions in S-Paired Fermi Systems
Autorzy:
Mulak, M.
Gonczarek, R.
Powiązania:
https://bibliotekanauki.pl/articles/1968488.pdf
Data publikacji:
1997-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
Opis:
The most general S-paired systems of fermions for which a gap equation can be separated according to the specific redefined variables, are considered. Moreover, a solution of this gap equation (gap energy) is obtained in a parametric form. It allows us to investigate thermodynamic properties of such systems i.e. the thermodynamic potential, entropy, heat capacity and critical magnetic induction. We show also that the heat capacity difference between the superconducting and the normal phase is entirely determined by the order parameter. The obtained results reveal possibilities of discontinuous phase transition to the normal state and moreover, the theorem on existence of such transitions is formulated and proved. The condition for the BCS-type energy gap is given, which additionally classifies properties of the heat capacity of S-paired phase by virtue of the shape of the energy gap. In order to illustrate the developed formalism, the numerical results for the so-called statistical spin liquids and application of the established methods to the experimental data conversion, are presented and discussed.
Źródło:
Acta Physica Polonica A; 1997, 92, 6; 1177-1189
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stable States for Superconducting Systems with Combined S-Wave and D-Wave Pairing. Zero Temperature Case
Autorzy:
Kumala, W.
Gonczarek, R.
Powiązania:
https://bibliotekanauki.pl/articles/1968863.pdf
Data publikacji:
1998-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
Opis:
The Fermi-liquid system with S-wave and D -wave pairing interaction harmonics is considered. The general equations for energy gap and thermodynamic potential difference for arbitrary temperatures are given. The detailed calculations are performed for zero-temperature limit. The obtained results are illustrated and discussed. The value and structure of energy gap are presented. It is showed that the anisotropic gap can be realized only for g$\text{}_{0}$ < g$\text{}_{2}$.
Źródło:
Acta Physica Polonica A; 1998, 93, 3; 539-546
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Possibility of Realization of d- or p-Wave Symmetry States in Anisotropic Superconductors
Autorzy:
Gonczarek, R.
Krzyzosiak, M.
Powiązania:
https://bibliotekanauki.pl/articles/2046732.pdf
Data publikacji:
2006-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Rp
74.62.Yb
Opis:
We consider a model of high-T$\text{}_{c}$ superconductors with an anisotropic boson-mediated pairing mechanism corresponding to the nearest-neighbor interactions, and the one-particle dispersion relation characterized by 2D Fermi surface nesting. Based upon the tight-binding or t-J approaches with half-filling we show that the effective pairing potential coefficients and the dispersion relation, which can be characterized by the parameterη=2t$\text{}_{1}$/t$\text{}_{0}$, have a diverse and mutually competing influence on the values of transition temperatures. The spin-singlet d-wave symmetry superconducting state is realized for small values ofη, whereas for sufficiently large values, the spin-triplet p-wave symmetry superconducting state should be formed. The specific heat jump and the isotope shift, as functions of the parameter η, are evaluated for the d- and p-wave symmetry.
Źródło:
Acta Physica Polonica A; 2006, 109, 4-5; 493-498
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structures of Thermodynamic Functions for S-Paired Fermi Systems in Parametric Equations Approach
Autorzy:
Mulak, M.
Gonczarek, R.
Powiązania:
https://bibliotekanauki.pl/articles/1945431.pdf
Data publikacji:
1996-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
Opis:
The general method of investigation of S-paired Fermi systems is given and discussed as generalization of parametric equation for the energy gap. The additional parametric equations for thermodynamic potential and heat capacity are obtained as functions of introduced parameters. The detailed calculations are given for a few exemplary chosen magnetic fields and superflows. Moreover, we consider the case of so-called statistical spin liquid, which constitutes non-BCS model.
Źródło:
Acta Physica Polonica A; 1996, 89, 5-6; 689-698
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Surface Roughness on Equilibrium States of Superfluid $\text{}^{3}$He in Confined Geometry
Autorzy:
Gonczarek, R.
Krzyżanowski, I. H.
Powiązania:
https://bibliotekanauki.pl/articles/1891638.pdf
Data publikacji:
1991-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
67.50.-b
67.50.Fi
Opis:
The superfluid $\text{}^{3}$He is considered in confined geometry for arbitrary thickness when surface roughness is taken into account. The equilibrium states, the critical size when the two-dimensional state is realized exclusively, and the critical thickness below which superfluidity is destroyed are defined, found and discussed with reference to the essential parameters of a system. Some particular cases are examined analytically. The examples of exact numerical solutions are presented.
Źródło:
Acta Physica Polonica A; 1991, 80, 4; 553-569
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Form and Properties of the Tight-Binding Density of States in Two Dimensions. Possible Application to Superconductivity
Autorzy:
Gładysiewicz, M.
Gonczarek, R.
Mulak, M.
Powiązania:
https://bibliotekanauki.pl/articles/2030728.pdf
Data publikacji:
2002-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.20.Fg
Opis:
The form of the density of states for a tight-binding model with the first and the next-nearest neighbour hoppings for a rectangular planar lattice and a shift of the chemical potential are calculated. This is newly and comprehensively formulated integral form illustrated numerically, helpful in approach to two-dimensional superconducting models. In some particular cases the complete analytical forms of the density of states are obtained. It is shown that for all cases the density of states has a single van Hove singularity of the logarithmic type at the identically defined point. The proper approximate analytical representations are found. The difference between the exact numerical and approximate analytical forms is evaluated and illustrated.
Źródło:
Acta Physica Polonica A; 2002, 101, 6; 865-874
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic Properties of D-Wave Paired Superconductors
Autorzy:
Gonczarek, R.
Mulak, M.
Kumala, W.
Powiązania:
https://bibliotekanauki.pl/articles/1994689.pdf
Data publikacji:
1999-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
Opis:
The D-wave paired Fermi system is considered in the frame of generalized gap equation obtained in a BCS-like approach. It is shown that the thermodynamic functions of a system, as the thermodynamic potential, entropy and heat capacity differences between the normal and superconducting state are precisely defined functionals of the energy gap as a function of temperature. The derived formulas are identical as those obtained for S-wave paired Fermi system. It states that the developed formalism can be applied, in practice, to investigation of real superconductors in which a singlet state is realized. Some numerical results illustrating prospects and capabilities of the presented formalism are given for chosen structures of the order parameter.
Źródło:
Acta Physica Polonica A; 1999, 95, 2; 231-242
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermodynamic Properties of D-Wave Paired Superconductors in the Low Temperature and Subcritical Regions
Autorzy:
Kumala, W.
Gonczarek, R.
Mulak, M.
Powiązania:
https://bibliotekanauki.pl/articles/2013257.pdf
Data publikacji:
2000-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
Opis:
D-wave paired isotropic Fermi system in the limiting cases T → T$\text{}_{c}$ and T → 0 is considered. Values of the energy gap, the thermodynamic potential, and the specific heat as a function of temperature are given for admissible solutions and compared with values for S-wave paired system. It is shown that the linear term of low temperature specific heat vanishes likewise in case of S-wave pairing. The obtained results make prospects to define the geometry of the energy gap in virtue of the behavior of the specific heat in the limiting temperature cases for heavy-fermion superconductors.
Źródło:
Acta Physica Polonica A; 2000, 97, 4; 693-703
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Form of Energy Gap and Critical Temperature of Superconductor Implied by Fluctuations of Density of States
Autorzy:
Gładysiewicz, M.
Gonczarek, R.
Mulak, M.
Powiązania:
https://bibliotekanauki.pl/articles/2014021.pdf
Data publikacji:
2000-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
Opis:
The s-paired BCS superconductor with the electron density of states depending on energy in the vicinity of Fermi level is considered. The existence of such fluctuations of electron density of states may be referred to Van Hove singularities widely discussed in the literature. In the paper three types of small fluctuations of the electron density of states introduced about its average background's value are analysed: Lorentzian, triangle, and logarithmic ones. In order to calculate numerically the energy gap and critical temperature, the formalism of parametric BCS gap equations is applied. The positive fluctuations (peaks) correspond to the increase in occupied states number inducing a higher critical temperature. On the other hand, negative fluctuations, which decrease the number of occupied states, lead to a lower critical temperature. Such decrease in critical temperature can lead, at a specific choice of parameters, to the decease in superconductivity. The presence of fluctuations finds reflection in the shape of energy gap as a function of temperature. In the vicinity of T=0 an abrupt decrease or increase in the energy gap to the original BCS value, according to the sign of the fluctuation, is observed. In turn, the fluctuations do not change the behaviour of the energy gap near T$\text{}_{c}$.
Źródło:
Acta Physica Polonica A; 2000, 97, 6; 1039-1051
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Response in Kinetic Energy Driven Superconductivity: the Meissner Effect
Autorzy:
Krzyzosiak, M.
Lan, Y.
Feng, S.
Jacak, L.
Gonczarek, R.
Powiązania:
https://bibliotekanauki.pl/articles/1536649.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Ha
74.25.N-
74.20.Mn
Opis:
Electromagnetic response of cuprate superconductors is studied within the model of kinetic energy driven d-wave superconductivity by analyzing the Meissner effect. The kernel of the linear response function is found and employed to calculate the magnetic field penetration depth and the superfluid density of cuprate superconductors within the specular reflection model for a purely transverse vector potential. It is shown that the magnetic field penetration depth and the superfluid density depend linearly on temperature, except for a strong deviation from the linear characteristics at extremely low temperatures, which is attributed to nonlocal effects. The zero-temperature superfluid density is found to decrease linearly with decreasing doping concentration in the underdoped regime. The problem of gauge invariance in the theoretical description of the electromagnetic response is addressed, and an approximation which does not violate local charge conservation is proposed.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 283-288
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-12 z 12

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