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Wyświetlanie 1-15 z 19
Tytuł:
Zero Temperature Phase Diagram of a d-Wave Superconductor with Anderson Impurities
Autorzy:
Borkowski, L.
Powiązania:
https://bibliotekanauki.pl/articles/1810398.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.81.-g
74.25.Dw
Opis:
We study the model of a d-wave superconductor interacting with finite concentration of the Anderson impurities at zero temperature. The interaction between impurity and conduction electrons is taken into account within the large-N approximation. We discuss the obtained phase diagram and its dependence on the main energy scales.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 120-122
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Breakdown of the Quantum Hall Effect
Autorzy:
Maude, D. K.
Rigal, L. B.
Desrat, W.
Potemski, M.
Portal, J. C.
Eaves, L.
Wasilewski, Z. R.
Toropov, A. I.
Hill, G.
Powiązania:
https://bibliotekanauki.pl/articles/2027467.pdf
Data publikacji:
2001-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Pm
74.25.Dw
Opis:
The breakdown of the dissipationless conductance in the integer and fractional quantum Hall effect regime is reviewed. The temperature dependence of the critical current and of the critical magnetic field at breakdown bears a striking resemblance to the phase diagram of the phenomenological two-fluid Gorter-Casimir model for superconductivity. In addition, a remarkably simple scaling law exists between different filling factors.
Źródło:
Acta Physica Polonica A; 2001, 100, 2; 213-226
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Van Hove Singularity and Superconductivity in Disordered Sr$\text{}_{2}$RuO$\text{}_{4}$
Autorzy:
Litak, G.
Annett, J. F.
Györffy, B. L.
Powiązania:
https://bibliotekanauki.pl/articles/2012935.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.62.Dh
74.25.Dw
74.25.Fy
Opis:
On the basis of a simple model we analyse the influence of disorder on critical temperature T$\text{}_{c}$ in p-wave superconductors. The disorder is treated by means of the coherent potential approximation and we focus our attention on the effect of a van Hove singularity near Fermi energy E$\text{}_{F}$. For the appropriate values of its parameters our model reproduces the experimentally found behaviour of Sr$\text{}_{2}$ RuO$\text{}_{4}$.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 249-252
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unconventional Superconductivity in Iron-Based Superconductors in a Three-Band Model
Autorzy:
Crivelli, D.
Ptok, A.
Powiązania:
https://bibliotekanauki.pl/articles/1374327.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Rp
74.70.Xa
74.25.Dw
Opis:
Iron-based superconductors exhibit features of systems where the Fulde-Ferrell-Larkin-Ovchinnikov phase, a superconducting state with non-zero total momentum of the Cooper pairs, is actively sought. Experimental and theoretical evidence points strongly to the Fulde-Ferrell-Larkin-Ovchinnikov phase in these materials above the Pauli limit. In this article we discuss the ground state of iron-based superconductors near the critical magnetic field and the full h-T phase diagram for pnictides in case of intra-band pairing, in a three-band model with $s_{±}$ symmetry.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-16-A-19
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coexistence of Spin-Triplet Superconductivity with Antiferromagnetism in Orbitally Degenerate System: Hartree-Fock Approximation
Autorzy:
Zegrodnik, M.
Spałek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1431255.pdf
Data publikacji:
2012-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.25.Dw
75.10.Lp
Opis:
We consider the coexistence of the Hund's-rule-exchange induced spin-triplet paired state with the antiferromagnetic ordering by starting from the extended Hubbard model for a doubly degenerate band. We use the density of states appropriate for the square lattice and treat the problem in the Hartree-Fock approximation. The temperature dependences of the superconducting gaps, the magnetic moment, and the chemical potential are presented. The free energy in the considered phase is evaluated, as well as the corresponding free energies in four additional phases: paramagnetic, ferromagnetic, superconducting of type A and superconducting of type A1 coexisting with ferromagnetism; they occur in the proper range of parameters: band filling n and the interaction parameters U/W and J/W. The low temperature values of the superconducting gaps and staggered magnetic moment are also analyzed as a function of band filling.
Źródło:
Acta Physica Polonica A; 2012, 121, 4; 801-804
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Electronic Structure on the Phase Diagram of Weakly Doped Superconducting Cuprates
Autorzy:
Maciąg, A. M.
Wróbel, P.
Powiązania:
https://bibliotekanauki.pl/articles/2047334.pdf
Data publikacji:
2007-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
74.20.Mn
74.25.Dw
Opis:
Motivated by the difference between the experimental phase diagram of cuprates and expectations of the t-J model, we analyze the influence of the electronic structure on superconducting state generation for small levels of doping. Following some theoretical studies of the Fermi surface for hole doped superconducting cuprates we base our calculations on the t-t'-t''-J model. We construct the spin polaron model, which is an effective model for the t-J model, and we expand it by adding the new terms related to the next neighbor hopping integrals t' and t''. In the framework of this model we study evolutions of superconducting correlation functions with doping. As a result of numerical calculations we find out that superconducting state vanishes for small levels of doping and finite values of t' and t''. This is in qualitative agreement with experimental results.
Źródło:
Acta Physica Polonica A; 2007, 111, 5; 721-725
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
t-t-J-U Model in Mean-Field Approximation: Coexistence of Superconductivity and Antiferromagnetism
Autorzy:
Abram, M.
Powiązania:
https://bibliotekanauki.pl/articles/1374335.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
74.25.Dw
74.72.Gh
Opis:
We discuss the t-J-U model in the mean-field approximation. The role of spin-exchange coupling J and the second nearest hopping t' are examined in the context of the coexistence of superconductivity and antiferromagnetism. Stability of the phases is studied with respect to temperature. The coexistence region exists for the sufficiently large Coulomb repulsion (U>$U_{cr}$), and in the vicinity of the half-filled band (hole doping δ < $δ_{cr}$). The critical hole doping is relatively small ($δ_{cr}$ ≈ 0.006 for J/|t| = 1/3) and linear with respect to J. The decrease of $U_{cr}$ is proportional to J, except the limit of small J (J/|t| < 0.03), where $U_{cr}$ grows rapidly with decreasing J. The effect of the second nearest hopping is limited - the phase diagram does not change in a qualitative manner when the t' value is changed. In the limit of T → 0, SC phase is stable even for large hole-doping (such as δ = 0.5). Additional paramagnetic phase appears for large δ or small U at non-zero temperature. When temperature increases, both SC and AF+SC phase regions are reduced.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-25-A-29
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mulliken Occupation as the Indicator of Transition to Superconducting State in SrFe₂As₂ and BaFe₂As₂
Autorzy:
Goraus, J.
Powiązania:
https://bibliotekanauki.pl/articles/1398653.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.40.Kb
71.15.Mb
74.25.Dw
Opis:
Basing on the ab initio calculations performed within full potential local orbital minimum basis method, the Mulliken occupation of the Sr 5s $(n_{5s})$ and Ba 6p $(n_{6p})$ states can serve as an indicator of transition to the superconducting state in doped SrFe₂As₂ and BaFe₂As₂ compounds where the iron was substituted with cobalt or in the pristine compounds under pressure. The estimated pressure, at which both compounds exhibit superconductivity based on Sr 5s and Ba 6p occupation is in good agreement with the recently published experimental data.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 655-658
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin-Triplet Pairing Induced by Hunds Rule Exchange in Orbitally Degenerate Systems: Hartree-Fock Approximation
Autorzy:
Zegrodnik, M.
Spałek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1426874.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.25.Dw
75.10.Lp
Opis:
We discuss the spin-triplet pairing mechanism induced by the Hund rule ferromagnetic exchange. We include explicitly the effect of interband hybridization and treat the problem by starting from an extended Hubbard model for a doubly degenerate band, making the simplest Hartree-Fock approximation for the part involving the pairing and the Hubbard interaction. The conditions of stability of various phases are determined as a function of both band filling and microscopic parameters. The phase diagram contains regions of stability of the spin-triplet superconducting phase coexisting with either saturated or non-saturated ferromagnetism. Phase diagrams for the cases of constant density of states and that of square lattice have been provided. The influence of hybridization on the stability of considered phases, as well as the temperature dependences of magnetic moment and the superconducting gap are also discussed.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1051-1055
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strongly Anisotropic S=1 (Pseudo) Spin Systems: from Mean Field to Quantum Monte-Carlo
Autorzy:
Panov, Yu.
Moskvin, A.
Konev, V.
Vasinovich, E.
Ulitko, V.
Powiązania:
https://bibliotekanauki.pl/articles/1030506.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Hk
75.10.Jm
74.25.Dw
Opis:
The S=1 pseudospin formalism was recently proposed to describe the charge degree of freedom in a model high-T_{c} cuprate with the on-site Hilbert space reduced to the three effective valence centers, nominally Cu^{1+;2+;3+}. With small corrections the model becomes equivalent to a strongly anisotropic S=1 quantum magnet in an external magnetic field. We have applied a generalized mean-field approach and quantum Monte-Carlo technique for the model 2D S=1 system to find the ground state phase with its evolution under deviation from half-filling and different correlation functions. Special attention is given to the role played by the on-site correlation ("single-ion anisotropy").
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 426-428
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Muon Spin Rotation Studies of the Vortex Matter in the High-T$\text{}_{c}$ Superconductor Bi$\text{}_{2}$Sr$\text{}_{2}$CaCu$\text{}_{2}$O$\text{}_{8+δ}$
Autorzy:
Blasius, T.
Niedermayer, Ch.
Tallon, J. L.
Pooke, D. M.
Golnik, A.
Noakes, D. R.
Stronach, C. E.
Ansaldo, E. J.
Henn, R. W.
Lin, C. T.
Bernhard, C.
Powiązania:
https://bibliotekanauki.pl/articles/2011022.pdf
Data publikacji:
1999-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.60.Ge
74.25.Dw
74.72.Hs
76.75.+i
Opis:
We report muon spin rotation studies of the magnetic field distribution n(B) in the vortex state of the high-temperature superconductor Bi$\text{}_{2}$Sr$\text{}_{2}$CaCu$\text{}_{2}$O$\text{}_{8+δ}$. From our data on three sets of overdoped, nearly optimized and underdoped single crystals we obtain evidence for a two-stage melting process of the vortex matter under equilibrium conditions. In the irreversible regime well below the irreversibility line we observe a transition in the vortex state which we associate with an intra-planar melting transition. The resulting flux-line liquid phase persists over a sizeable temperature interval before the inter-planar decoupling of the individual vortex lines takes place in a second step at the irreversibility line, resulting in a pancake liquid phase.
Źródło:
Acta Physica Polonica A; 1999, 96, 2; 245-258
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground State Phase Diagram of the Extended Hubbard Model with Pair-Hopping Interaction in the Limit of Very Narrow Bandwidth
Autorzy:
Kapcia, K.
Czart, W.
Powiązania:
https://bibliotekanauki.pl/articles/1398642.pdf
Data publikacji:
2016-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
71.10.Hf
74.20.-z
74.25.Dw
Opis:
The extended Hubbard model with the pair-hopping interaction, i.e. the Penson-Kolb-Hubbard model, is one of the conceptually simplest phenomenological models for studying correlations and for description of superconductivity in very narrow-band systems with short-range, almost unretarded pairing. We present ground state phase diagrams of the model derived within the broken-symmetry Hartree-Fock approximation in the narrow-bandwidth regime and compare these results with the exact ones in the atomic limit for the limit of high dimensions. The investigation of the diagrams of the model show that results obtained within both approaches are consistent, although for the case of the finite single-electron hopping phases with magnetic long-range order also occur.
Źródło:
Acta Physica Polonica A; 2016, 130, 2; 617-620
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Fulde-Ferrell-Larkin-Ovchinnikov Superconductivity in Disordered Systems
Autorzy:
Ptok, A.
Powiązania:
https://bibliotekanauki.pl/articles/1537270.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.Fg
74.20.Mn
74.20.Rp
74.25.Dw
74.81.-g
Opis:
The Fulde-Ferrell-Larkin-Ovchinnikov phase, with a spatially oscillating order parameter, may be induced by strongly magnetic field at low temperature. It is believed that the Fulde-Ferrell-Larkin-Ovchinnikov phase can exist only in homogeneous superconductors, and even weak impurity potential can lead to its destruction. The analysis of the Fulde-Ferrell-Larkin-Ovchinnikov phase in the Bogoliubov-de Gennes equation shows however, that this phase can exist in the presence of weak disorder. Using Bogoliubov-de Gennes equations, we discussed the influence of diagonal and off-diagonal disorder on the Fulde-Ferrell-Larkin-Ovchinnikov phase.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 420-422
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mixed State in t-U-J-V Model
Autorzy:
Tobijaszewska, B.
Bak, M.
Powiązania:
https://bibliotekanauki.pl/articles/1810406.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.20.-z
74.20.Rp
74.25.Dw
71.10.Fd
71.27.+a
Opis:
The t-U-J-V model in the U → ∞ limit is treated by renormalized mean-field theory for arbitrary electron density. Superconductivity of s+id symmetry is found in the large parts of the phase diagram. Calculations also show a possibility of phase separation.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 135-137
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Superconductivity, Metastability and Magnetic Field Induced Phase Separation in the Atomic Limit of the Penson-Kolb-Hubbard Model
Autorzy:
Kapcia, K.
Powiązania:
https://bibliotekanauki.pl/articles/1374357.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
74.20.-z
64.75.Gh
71.10.Hf
74.25.Dw
Opis:
We present the analysis of paramagnetic effects of magnetic field (B) (Zeeman term) in the zero-bandwidth limit of the extended Hubbard model for arbitrary chemical potential μ and electron density n. The effective Hamiltonian considered consists of the on-site interaction U and the intersite charge exchange term I, determining the hopping of electron pairs between nearest-neighbour sites. The model has been analyzed within the variational approach, which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation (rigorous in the limit of infinite dimensions d → +∞). In this report we focus on metastable phases as well as phase separated states involving superconducting and nonordered phases and determine their ranges of occurrence for U/$I_0$=1.05 ($I_0$=zI) in the presence of magnetic field B≠0. Our investigations of the general case for arbitrary U/$I_0$ show that, depending on the values of interaction parameters (for fixed n), the phase separating state can occur in higher fields than the homogeneous superconducting phase (field-induced phase separated). Moreover, a first-order superconducting-nonordered transition occurs between metastable phases and these metastable phases can exist inside the regions of the phase separated state stability. Such behaviour is associated with the presence of tricritical line on the phase diagrams of the system.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-53-A-57
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 19

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