共查询到20条相似文献,搜索用时 16 毫秒
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O. S. Barišić S. Barišić 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(1):1-18
The behavior of the 1D Holstein polaron is described, with emphasis on lattice coarsening effects, by distinguishing between
adiabatic and nonadiabatic contributions to the local correlations and dispersion properties. The original and unifying systematization
of the crossovers between the different polaron behaviors, usually considered in the literature, is obtained in terms of quantum
to classical, weak coupling to strong coupling, adiabatic to nonadiabatic, itinerant to self-trapped polarons and large to
small polarons. It is argued that the relationship between various aspects of polaron states can be specified by five regimes:
the weak-coupling regime, the regime of large adiabatic polarons, the regime of small adiabatic polarons, the regime of small
nonadiabatic (Lang-Firsov) polarons, and the transitory regime of small pinned polarons for which the adiabatic and nonadiabatic
contributions are inextricably mixed in the polaron dispersion properties. The crossovers between these five regimes are positioned
in the parameter space of the Holstein Hamiltonian. 相似文献
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Based on the integrable Gaudin model and local density approximation, we discuss the ground state of a one-dimensional trapped Fermi gas with imbalanced spin population, for an arbitrary attractive interaction. A phase separation state, with a polarized superfluid core immersed in an unpolarized superfluid shell, emerges below a critical spin polarization. Above it, coexistence of polarized superfluid matter and a fully polarized normal gas is favored. These two exotic states could be realized experimentally in highly elongated atomic traps, and diagnosed by measuring the lowest density compressional mode. We identify the polarized superfluid as having an Fulde-Ferrell-Larkin-Ovchinnikov structure, and predict the resulting mode frequency as a function of the spin polarization. 相似文献
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This model is a variant on Baker's lattice model for liquids; it takes certain features of water into account by means of a hydrogen-bond parameter in the Hamiltonian. Solutions for the complete phase diagram are obtained by means of the cluster variation method. The model displays three phases chosen to correspond with the vapor, open ice and liquid state. The isotherms show a density maximum. We discuss the shortcomings of the model and what to do about them. 相似文献
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C. Guiot 《Il Nuovo Cimento D》1985,6(1):1-16
Summary The two 1-dimensional spin systems proposed by Aharonov and Schwartz as models of confinement isomorphic with the MIT bag
model are thoroughly analysed by using an improved mean-field scheme (which has the customary mean-field theory as its zero-th-order
approximation), recently suggested to deal with fluctuation in a perturbative cluster-cumulant aproach. The ground state and
its phase diagram are discussed in detail.
Riassunto I due modelli di spin unidimensionali proposti da Aharonov e Schwartz come modelli di confinamento isomorfi al ?MIT bag model? sono analizzati compiutamente mediante uno schema di campo medio migliorato (che ammette l’ordinaria teoria di campo medio come approssimazione di ordine zero), elaborato recentemente per trattare le fluttuazioni con un approccio perturbativo che utilizza il calcolo dei cumulanti su grappoli. Lo stato fondamentale ed il corrispondente diagramma di fase sono discussi in dettaglio.
Реэюме Проводится аналиэ двух одномерных спиновых систем, предложенных Аароновым и Щварцем в качестве моделей удержания, иэоморфного в случае MIT-модели ?мешка?. Для аналиэа исполыэуется усовершенствованная схема среднего поля (в которой обычная теория среднего поля чредставляет приближение нулевого порядка). Эта схема была недавно предложена для рассмотрения флуктуаций в пертурбационном кластерном подходе. Подробно обсуждаются основное состояние и соответствуюшая фаэовая диаграмма.相似文献
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It is shown that the large- N approach yields two energy scales for the Kondo lattice model. The single-impurity Kondo temperature, T(K), signals the onset of local singlet formation, while Fermi-liquid coherence sets in only below a lower scale, T small star, filled. At low conduction electron density n(c) ("exhaustion" limit), the ratio T small star, filled/T(K) is much smaller than unity, and is shown to depend only on n(c) and not on the Kondo coupling. The physical meaning of these two scales is demonstrated by computing several quantities as a function of n(c) and temperature. 相似文献
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《Nuclear Physics B》2002,639(3):411-428
Phase transitions can occur in one-dimensional classical statistical mechanics at non-zero temperature when the number of components N of the spin is infinite. We show how to solve such magnets in one dimension for any N, and how the phase transition develops at N=∞. We discuss SU(N) and Sp(N) magnets, where the transition is second-order. In the new high-temperature phase, the correlation length is zero. We also show that for the SU(N) magnet on exactly three sites with periodic boundary conditions the transition becomes first order. 相似文献
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A. Kalz A. Honecker S. Fuchs T. Pruschke 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):533-537
We restudy the phase diagram of the 2D-Ising model with competing interactions J1 on nearest neighbour and J2 on next-nearest neighbour bonds via Monte-Carlo simulations. We present the finite temperature phase diagram and introduce
computational methods which allow us to calculate transition temperatures close to the criticalpoint at J2 = J1/2. Further on we investigate the character of the different phase boundariesand find that the transition is weakly first
order formoderate J2 > J1/2. 相似文献
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Straley JP 《Physical review. B, Condensed matter》1994,49(9):5806-5810
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Nakatsuji S Yeo S Balicas L Fisk Z Schlottmann P Pagliuso PG Moreno NO Sarrao JL Thompson JD 《Physical review letters》2002,89(10):106402
The La dilution of the Kondo lattice CeCoIn5 is studied. The scaling laws found for the magnetic susceptibility and the specific heat reveal two well-separated energy scales, corresponding to the single-impurity Kondo temperature T(K) and an intersite spin-liquid temperature T(*). The Ce-dilute alloy has the expected Fermi liquid ground state, while the specific heat and resistivity in the dense Kondo regime exhibit non-Fermi-liquid behavior, which scales with T(*). These observations indicate that the screening of the magnetic moments in the lattice involves antiferromagnetic intersite correlations with a larger energy scale in comparison with the Kondo impurity case. 相似文献
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Y. Tanaka A. Crisan D.D. Shivagan A. Iyo P.M. Shirage K. Tokiwa T. Watanabe N. Terada 《Physica C: Superconductivity and its Applications》2009,469(15-20):1129-1131
On a superconducting bi-layer with thickness much smaller than the penetration depth, λ, a vortex molecule might form. A vortex molecule is composed of two fractional vortices and a soliton wall. The soliton wall can be regarded as a Josephson vortex missing magnetic flux (degenerate Josephson vortex) due to an incomplete shielding. The magnetic energy carried by fractional vortices is less than in the conventional vortex. This energy gain can pay a cost to form a degenerate Josephson vortex. The phase diagram of the vortex molecule is rich because of its rotational freedom. 相似文献