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Wyświetlanie 1-15 z 25
Tytuł:
Studies on Isotope Shift Exponent and Pressure Coefficient for Extended Superconductors within BCS Formalism
Autorzy:
Banerjee, B.
Roy, S.
Powiązania:
https://bibliotekanauki.pl/articles/1808029.pdf
Data publikacji:
2009-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.+f
74.25.Bt
74.25.Ha
Opis:
A tight-binding model comprising a hopping and an attractive interaction term was considered for high temperature superconductors. Explicit calculations on the effects of isotopic substitution of atoms and application of pressure on the transition temperatures were made in this work. Exact analytical expressions for the isotope-shift exponent (α) and pressure coefficient $(γ_P)$ of transition temperature $(T_C)$ considering the isotopic mass and pressure dependence of the hopping and attractive interaction strengths from a minimal model describing superconductivity were obtained. Theoretical predictions for α and $γ_P$ with proper choice of parameters are found to be qualitatively consistent with the results of the experiments of high $T_C$ oxides. The results depend on the band dispersion chosen.
Źródło:
Acta Physica Polonica A; 2009, 115, 5; 914-919
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characteristics of the Eliashberg Formalism on the Example of High-Pressure Superconducting State in Phosphor
Autorzy:
Duda, A.
Szczęśniak, R.
Sowińska, M.
Domagalska, I.
Powiązania:
https://bibliotekanauki.pl/articles/1398651.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Fg
74.25.Bt
74.62.Fj
Opis:
The work describes the properties of the high-pressure superconducting state in phosphor: p∈ {20, 30, 40, 70} GPa. The calculations were performed in the framework of the Eliashberg formalism, which is the natural generalization of the BCS theory. The exceptional attention was paid to the accurate presentation of the used analysis scheme. With respect to the superconducting state in phosphor it was shown that the observed not-high values of the critical temperature ([T_{C}]_{p=30GPa}^\text{max}=8.45 K) result not only from the low values of the electron-phonon coupling constant, but also from the very strong depairing Coulomb interactions. Additionally the inconsiderable strong-coupling and retardation effects force the dimensionless ratios $R_{Δ}$, $R_{C}$, and $R_{H}$ - related to the critical temperature, the order parameter, the specific heat, and the thermodynamic critical field - to take the values close to the BCS predictions.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 649-654
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Magnetic Penetration Depth in Superconducting Ultrathin Lead Films
Autorzy:
Durajski, A.
Szczęśniak, R.
Powiązania:
https://bibliotekanauki.pl/articles/1032804.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Fg
74.25.Bt
74.62.Fj
Opis:
In the present paper, we report a theoretical study of the magnetic London penetration depth in ultrathin Pb films consisting of five to ten monolayers. Our calculations were performed within the framework of the strong-coupling approach. We observed that for thin films, the thermodynamic parameter exhibits an oscillatory behaviour connected with a quantum size effect. Moreover, we proved that the London penetration depth of Pb films cannot be correctly described using the Bardeen-Cooper-Schrieffer theory of superconductivity due to the strong-coupling and retardation effects. The Eliashberg theory, used in this paper, goes beyond the BCS theory to include these effects which allows to describe the superconducting state on the quantitative level.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 1051-1053
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Thermodynamic Critical Field for the $K_3C_{60}$ and $Rb_3C_{60}$ Fullerides
Autorzy:
Durajski, A.
Szczęśniak, R.
Powiązania:
https://bibliotekanauki.pl/articles/1371531.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Fg
74.25.Bt
74.62.Fj
Opis:
In the paper the temperature dependence of the thermodynamic critical field ($H_c$) for the alkali-metal-doped fullerides $K_3C_{60}$ and $Rb_3C_{60}$ has been considered. The numerical calculations have been conducted in the framework of the Migdal-Eliashberg formalism. It has been shown that the obtained numerical values of $H_c$ agree with the experimental data. Finally, the dimensionless ratio: $R_{H}$ ≡ $T_cC^{N}$ ($T_c$)/$H_c^{2}(0)$ has been calculated, where $T_c$ is the critical temperature and $C^{N}$ denotes the specific heat in the normal state. The theoretical analysis has proved that for the considered fullerides the parameter $R_{H}$ is beyond the BCS prediction. In particular: $R_{H}$=0.143 for $K_3C_{60}$, and $R_{H}$=0.145 for $Rb_3C_{60}$.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 342-343
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconducting parameters of spinel CuRh₂S₄ under pressure
Autorzy:
Ito, M.
Taira, A.
Sonoda, K.
Powiązania:
https://bibliotekanauki.pl/articles/1054874.pdf
Data publikacji:
2017-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Dd
74.62.Fj
74.25.Bt
Opis:
We investigated the magnetic properties of chalcogenide-spinel superconductor CuRh₂S₄ under pressure and estimated the pressure dependence of the superconducting parameters. With increasing pressure, the superconducting transition temperature (T_{c}), thermodynamic critical field (H_{c}), upper critical field (H_{c2}), penetration depth (λ), and GL parameter (κ) increase. Meanwhile, the lower critical field (H_{c1}) is unchanged and the Ginzburg-Landau coherence length (ξ_{GL}) is reduced by pressurization. The increasing value of κ indicates enhanced characteristics of the type-II superconductor CuRh₂S₄.
Źródło:
Acta Physica Polonica A; 2017, 131, 6; 1450-1453
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Properties of the Superconducting State in $YNi_2B_2C$: The One-Band Eliashberg Approach
Autorzy:
Jarosik, M.
Szczęśniak, R.
Powiązania:
https://bibliotekanauki.pl/articles/1505119.pdf
Data publikacji:
2011-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Fg
74.25.Bt
74.25.Ha
Opis:
The basic thermodynamic parameters of the superconducting state in $YNi_2 B_2 C$ were calculated in the framework of the one-band Eliashberg model. The effective Eliashberg function, determined on the basis of the transport function, was used during calculations. It was shown that the dimensionless ratios are equal to: $R_1$ ≡ 2Δp(0)/$k_{B}$ $T_{C}$ = 3.87, $R_2$ ≡ ΔC($T_{C})//C^{N}(T_{C})$ = 1.79 and $R_3$ ≡ $T_{C} C^{N}(T_{C}) // H_{C}^2(0)$ = 0.159. The value $R_1$ fairly agrees with the experimental data whereas $R_2$ and $R_3$ agree very well.
Źródło:
Acta Physica Polonica A; 2011, 119, 6; 863-867
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Thermodynamic Critical Field οf $YNi_2B_2C$ Superconductor
Autorzy:
Jarosik, M.
Szczęśniak, R.
Szczęśniak, D.
Powiązania:
https://bibliotekanauki.pl/articles/1535384.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Fg
74.25.Bt
74.25.Ha
Opis:
In the presented work the dependence of the thermodynamic critical field $(H_{C})$ on the temperature for the $YNi_2B_2C$ superconductor was determined in the framework of the Eliashberg formalism. The numerical calculations were conducted with the use of the modified transport Eliashberg function. It has been stated that the normalized field function $H_{C}(T)//H_{C}(0)$ correctly reproduces the experimental data.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 1031-1033
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reversible Magnetization of Melt-Processed NEG-123 Superconductor
Autorzy:
Jirsa, M.
Rameš, M.
Muralidhar, M.
Kacmarcik, J.
Marcenat, Ch.
Powiązania:
https://bibliotekanauki.pl/articles/1535270.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Ha
74.25.Bt
74.25.Op
Opis:
Specific heat of superconducting electrons was measured in a melt-processed $(Nd_{0.33}Eu_{0.38}Gd_{0.28})Ba_2Cu_3O_{y}$ superconductor (NEG-123) with 5 mol% of Gd-211, 1 wt% Ag, and 0.035 mol% of Zn. The thermodynamic characteristics of this compound are still not well known. From calorimetric measurements the reversible magnetization, critical fields, penetration depth, and coherence length were deduced. In the vicinity of $T_{c}$, the reversible magnetic moment was additionally measured by means of SQUID.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 1022-1023
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Specific Heatof the Filled Skutterudite Superconductor LaOs₄As₁₂
Autorzy:
Juraszek, J.
Henkie, Z.
Cichorek, T.
Powiązania:
https://bibliotekanauki.pl/articles/1398630.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Bt
74.70.Dd
Opis:
We investigated low-temperature specific heat of the filled skutterudite compound LaOs₄As₁₂ with a transition temperature $T_{c}$ = 3.2 K. A moderate size of a specific-heat jump points at a weak electron-phonon coupling in this material. At T < $T_{c}$, the electronic contribution to the specific heat was found to be at variance with the predictions for an s-wave superconductor with one energy gap. Additionally, we observed an upward curvature of the upper critical field near the transition temperature. Both features provide some indications towards multiband superconductivity, although anisotropy effects as a viable cause of the observed anomalies in LaOs₄As₁₂ cannot be excluded. Similarities to a probable two-band superconductor LaRu₄As₁₂ are discussed.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 597-599
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
AC Microcalorimetry of Superconducting $MgCNi_3$ Single Crystals
Autorzy:
Kačmarčík, J.
Pribulová, Z.
Samuely, P.
Marcenat, C.
Klein, T.
Jang, D.
Lee, H.
Lee, S.
Powiązania:
https://bibliotekanauki.pl/articles/1813689.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.70.Ad
74.25.Bt
Opis:
The low-temperature specific heat of single-crystal samples of superconducting $MgCNi_3$ with typical dimensions 200 μm were measured for the first time. A computer controlled ac microcalorimeter using an optical fiber and an infrared light-emitting diode as the heat source was used down to 2 K at magnetic fields up to 8 T. The specific heat data suggest a moderate coupling in $MgCNi_3$.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 363-366
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Specific Heat Study of Superconductivity in $Cu_{0.061}TiSe_{2}$
Autorzy:
Kačmarčík, J.
Pribulová, Z.
Pal'uchová, V.
Husaníková, P.
Karapetrov, G.
Komanický, V.
Samuely, P.
Powiązania:
https://bibliotekanauki.pl/articles/1371314.pdf
Data publikacji:
2014-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ga
74.25.Bt
71.45.Lr
Opis:
In $TiSe_{2}$ a charge-density-waves order is continuously suppressed by copper doping and superconductivity appears. We report a calorimetric study performed on the superconducting single crystal of $Cu_{0.061}TiSe_{2}$ with $T_{c}$=2.8 K, measured by the ac technique at low temperatures down to 0.6 K and magnetic fields up to 2 T. Sharp specific heat anomaly at the superconducting transition is found. The temperature dependence of the electronic specific heat and the angular dependence of the critical temperature, measured at a fixed magnetic field, consistently indicate on the existence of a single s-wave superconducting gap with a coupling strength of 2Δ/$k_{B}T_{c}$=3.6, close to BCS limit.
Źródło:
Acta Physica Polonica A; 2014, 126, 1; 322-323
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Isotope Effect of Disordered Superconductors
Autorzy:
Mierzyńska, M.
Wysokiński, K. I.
Powiązania:
https://bibliotekanauki.pl/articles/2038392.pdf
Data publikacji:
2004-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Bt
74.62.-c
74.62.Dh
Opis:
The isotope effects in disordered weak and strong coupling superconductors of different symmetries of the order parameter have been studied. We have found that even though weak localisation corrections to Eliashberg equations describe a strong degradation of transition temperature with disorder of s-wave superconductors, their influence on isotope coefficient is relatively weak. On the other hand the calculated change of relative isotope coefficient with T$\text{}_{c}$/T$\text{}_{c0}$ in homogeneous thin film materials is similar to that observed in high temperature superconductors.
Źródło:
Acta Physica Polonica A; 2004, 106, 5; 647-652
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pressure Dependence of the Thermodynamic Critical Field in Francium
Autorzy:
Pach, P.
Szczęśniak, R.
Durajski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1384843.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Fg
74.25.Bt
74.62.Fj
Opis:
In the paper, the values of the thermodynamic critical field $(H_{C})$ for francium have been calculated. It has been assumed the wide range of the pressure: p∈ ⟨7.2; 14⟩ GPa. The analysis has been performed in the framework of the strong-coupling formalism. It has been predicted that the value of the ratio $H_{C}(0)$/√ρ(0) increases with the increasing pressure from 3.08 meV to 5.84 meV, where ρ(0) denotes the electron density of states at the Fermi level. The dimensionless parameter $T_{C}C^{N}(T_{C})$/$H²_{C}(0)$ is smaller than in the BCS theory and decreases with pressure from 0.150 to 0.141. The symbol $T_{C}$ represents the critical temperature and $C^{N}$ is the specific heat for the normal state.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 231-233
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-Gap Superconductivity in $2H-NbS_2$
Autorzy:
Pribulová, Z.
Leroux, M.
Kačmarčík, J.
Marcenat, C.
Klein, T.
Rodière, P.
Cario, L.
Samuely, P.
Powiązania:
https://bibliotekanauki.pl/articles/1535279.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Bt
74.70.Ad
Opis:
We performed specific heat measurements of the superconducting single crystal of $2H-NbS_2$ in the temperature range down to 0.6 K and magnetic fields up to 14 T. The temperature and magnetic field dependence of the electronic specific heat consistently indicate existence of two superconducting energy gaps in the system. The superconducting anisotropy depends on both temperature and magnetic field. Moreover, the angular dependence of the upper critical field deviates from the Ginzburg-Landau behavior and rather reminds that of $MgB_2$. All these features point to a multigap superconductivity in $2H-NbS_2$. Our measurements are in a perfect agreement with the previous scanning tunneling spectroscopy of Guillamón et al.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 1024-1025
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monte Carlo Study of a Periodically Pinned 2D Superconductor
Autorzy:
Rezlescu, N.
Anghelache, R.
Ciobotaru, I.
Powiązania:
https://bibliotekanauki.pl/articles/1955503.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.Fr
75.10.Hk
74.25.Bt
Opis:
We show that a natural assumption on the moving mechanism of vortices in a periodically pinned, two-dimensional superconductor in the mixed state is the basis for a n-clock-like model. The pinning points are considered to be centered in each unit cell of the superconducting lattice. This property enables one to use a discrete version of the XY model used in the simulations focusing on the melting of the Abrikosov lattice of vortices in a system of Josephson arrays. A Monte Carlo study performed on the corresponding Hamiltonian in a field given by a filling factor of f=1/2 exhibits two phase transitions, at the temperatures T$\text{}_{c1}$≈0.325 and T$\text{}_{m}$≈0.65. The numerical estimation of the Challa parameters for both transitions indicates their continuous nature. The physical meaning of the lower transition is the expulsion of the magnetic field from the superconducting system, i.e. the Meissner effect. The physical equivalent of the upper transition is the melting of the pinned vortex lattice.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 337-340
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 25

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