Temat: 71.10.Hf - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Intriguing Magnetoresistivity of $URh_{0.62}Ru_{0.38}Ge$ in the Non-Fermi Liquid Regime
Autorzy:: Miiller, W.
Tran, V.
Tematy:: 71.10.Hf
71.20.Lp
71.27.+a; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1810409.pdf Link otwiera się w nowym oknie
Opis:: Magnetoresistivity of $URh_{0.62}Ru_{0.38}Ge$ solid solution was measured in the temperature range 0.35-300 K and in magnetic fields up to 9 T. For the studied system, which lies on the border of ferromagnetism, we observe positive magnetoresistivity in the non-Fermi liquid regime. The finding is in striking disagreement with scenario predicted for ferromagnetic quantum critical point.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Two-Band Model for Coherent Excitonic Condensates
Autorzy:: Apinyan, V.
Kopeć, T.
Tematy:: 71.10.Fd
71.28.+d
71.35.-y
71.10.Hf; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398643.pdf Link otwiera się w nowym oknie
Opis:: We consider the excitonic correlations in the two-band solid state system composed of the valence band and conduction band electrons. We treat the phase coherence mechanism in the system by presenting the electron operator as a fermion attached to the U(1) phase-flux tube. The emergent bosonic gauge field, related to the phase variables appears to be crucial for the coherent Bose-Einstein condensation of excitons. We calculate the normal excitonic Green functions, and the single-particle density of states functions being a convolution between bosonic and fermionic counterparts. We obtain the total density of states as a sum of two independent parts. For the coherent normal fermionic density of states, there is no hybridization-gap found in the system due to strong coherence effects and phase stiffness.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: On the BCS-BEC Crossover in the 2D Asymmetric Attractive Hubbard Model
Autorzy:: Kujawa-Cichy, A.
Tematy:: 71.10.Fd
74.20.Rp
71.27.+a
71.10.Hf; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1426931.pdf Link otwiera się w nowym oknie
Opis:: We analyze the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs in the 2D asymmetric attractive Hubbard model, in the presence of the Zeeman magnetic field (h). The broken symmetry Hartree approximation is used. We also apply the Kosterlitz-Thouless scenario to determine the phase coherence temperatures. We obtain that for the spin dependent hopping integrals $(t^{↑} ≠ t^{↓})$ the homogeneous polarized superfluid $(SC_{M})$ phase in the ground state for the strong attraction and lower filling can be stabilized. We find a topological quantum phase transition (the Lifshitz type) from the unpolarized superfluid phase $(SC_0)$ to $SC_{M}$ and tricritical point in the (h - μ) and spin polarization (P) vs. attraction (U < 0) ground state phase diagrams. The finite temperatures phase diagrams for $t^{↑} ≠ t^{↓}$ are constructed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: On the Imbalanced d-Wave Superfluids Within the Spin Polarized Extended Hubbard Model: Weak Coupling Limit
Autorzy:: Kujawa-Cichy, A.
Tematy:: 71.10.Fd
74.20.Rp
71.27.+a
71.10.Hf; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1431324.pdf Link otwiera się w nowym oknie
Opis:: We investigate the superfluid properties of d-wave pairing symmetry within the Extended Hubbard Model (EHM) in a magnetic field. We analyze the temperature and magnetic field dependencies of the order parameter. We find that in the two-dimensional case, the spatially homogeneous spin polarized superfluidity (SC(P≠0)) is stable in the weak coupling limit, at T=0, as opposed to the s-wave pairing symmetry case in 2D. We construct the ground state phase diagrams both for fixed chemical potential and electron concentration. Furthermore, we obtain the temperature vs. magnetic field and temperature vs. spin polarization phase diagrams.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Properties of the Bound States on a Hexagonal Lattice
Autorzy:: Bak, M.
Tematy:: 71.10.Fd
74.20.Rp
71.27.+a
71.10.Hf; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2047341.pdf Link otwiera się w nowym oknie
Opis:: Two electrons on a lattice pose an interesting problem which can be solved exactly. When the effective interactions are strong enough, the bound states are formed. The properties of such bound pairs in an extended Hubbard model are examined for both signs of nearest neighbor hopping integral t. The stabilization of s*-wave pairing is found for t<0 and of f-wave for t>0. Phase diagrams for the existence of none, one or two s*-wave solutions are calculated.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Heavy Quasiparticles in Yb Compounds: The Renormalized Band Approach
Autorzy:: Zwicknagl, G.
Tematy:: 71.10.+w
71.10.Hf
71.27.+a
75.30.Mb; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1368787.pdf Link otwiera się w nowym oknie
Opis:: Results for the magnetic-field-induced changes of the heavy quasiparticles in $YbRh_{2}Si_{2}$ are presented. The bands are determined by means of the Renormalized Band method. The progressive de-renormalization of the quasiparticles in the magnetic field, as well as the many-body enhancement of the Zeeman splitting are accounted for, using field-dependent quasiparticle parameters deduced from Numerical Renormalization Group studies.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Mixed Phase and Bound States in the Phase Diagram of the Extended Hubbard Model
Autorzy:: Bąk, M.
Tematy:: 71.10.Fd
71.10.Hf
71.27.+a; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1857970.pdf Link otwiera się w nowym oknie
Opis:: The paper examines part of the ground state diagram of the extended Hubbard model, with the on-site attraction U<0 and intersite repulsion W>0 in the presence of charge density waves, superconducting andη-superconducting order parameters. We show the possibility of the stabilization of the mixed state, with all three nonzero order parameters, in the model with nearest neighbor interactions. The other result of the paper is application of the exact solution of the Schrödinger equation for the two-electron bound state, as an additional bound for the phase diagram of the model, resulting in the partial suppression of the superconducting state of the s-wave symmetry, in favor of the normal state phase.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

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.
Tematy:: 71.10.Fd
71.10.Hf
74.20.-z
74.25.Dw; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398642.pdf Link otwiera się w nowym oknie
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.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Some Exact Results for the Zero-Bandwidth Extended Hubbard Model with Intersite Charge and Magnetic Interactions
Autorzy:: Kapcia, K.
Kłobus, W.
Robaszkiewicz, S.
Tematy:: 71.10.Fd
71.10.-w
71.10.Hf
71.45.Lr
75.30.Fv; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1385252.pdf Link otwiera się w nowym oknie
Opis:: The extended Hubbard model in the zero-bandwidth limit is studied. The effective Hamiltonian consists of (i) on-site U interaction, (ii) intersite density-density interaction W, and (iii) Ising-like magnetic exchange interaction J between the nearest-neighbors. We present rigorous (and analytical) results obtained within the transfer-matrix method for 1D chain in two particular cases: (a) W=0 and n=1; (b) U → +∞ and n=1/2 (W ≠ 0, J ≠ 0). We obtain the exact formulae for the partition functions which enables to calculate thermodynamic properties such as entropy, specific heat (c), and double occupancy per site. In both cases the system exhibits an interesting temperature dependence of c involving a characteristic two-peak structure. There are no phase transitions at finite temperatures and the only transitions occur in the ground state.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Stable and Metastable Phases in the Atomic Limit of the Extended Hubbard Model with Intersite Density-Density Interactions
Autorzy:: Kapcia, K.
Robaszkiewicz, S.
Tematy:: 71.10.Fd
71.45.Lr
64.60.My
64.75.Gh
71.10.Hf; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1426712.pdf Link otwiera się w nowym oknie
Opis:: We have studied a simple effective model of charge ordered insulators. The tight binding Hamiltonian consists of the effective on-site interaction U and the intersite density-density interaction $W_{ij}$ (both: nearest-neighbor and next-nearest-neighbor). In the analysis of the phase diagrams and thermodynamic properties of this model we have adopted the variational approach, which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation. Our investigations of the general case (as a function of the electron concentration n) have shown that the system exhibits various critical behaviors including among others bicritical, tricritical, critical-end, and isolated critical points. In this report we concentrate on the metastable phases and transitions between them. One finds that the first- and second order transitions between metastable phases can exist in the system. These transitions occur in the neighborhood of first as well as second order transitions between stable phases. For the case of on-site attraction the regions of metastable homogeneous phases occurrence inside the ranges of phase separated states stability have been also determined.
Dostawca treści:: Biblioteka Nauki

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