Zobrazeno 1 - 10
of 582
pro vyhledávání: '"Tognetti, V"'
Publikováno v:
Phys. Rev. A 74, 022322 (2006)
We study the pairwise entanglement close to separable ground states of a class of one dimensional quantum spin models. At T=0 we find that such ground states separate regions, in the space of the Hamiltonian parameters, which are characterized by qua
Externí odkaz:
http://arxiv.org/abs/cond-mat/0602268
The weak localization correction to the conductivity of a granular metal is calculated using the diagrammatic technique in the reciprocal grain lattice representation. The properties of this correction are very similar to that one in disordered metal
Externí odkaz:
http://arxiv.org/abs/cond-mat/0504169
Publikováno v:
Phys. Rev. B 72, 134510 (2005)
The first-order superconducting fluctuation corrections to the thermal conductivity of a granular metal are calculated. A suppression of thermal conductivity proportional to $T_c/(T-T_c)$ is observed in a region not too close to the critical temperat
Externí odkaz:
http://arxiv.org/abs/cond-mat/0503218
Publikováno v:
Eur. Phys. J. B 20, 55 (2001)
We consider quantum Heisenberg ferro- and antiferromagnets on the square lattice with exchange anisotropy of easy-plane or easy-axis type. The thermodynamics and the critical behaviour of the models are studied by the pure-quantum self-consistent har
Externí odkaz:
http://arxiv.org/abs/cond-mat/0101430
Spin dynamics and magnetic correlation length in two-dimensional quantum Heisenberg antiferromagnets
Autor:
Carretta, P., Ciabattoni, T., Cuccoli, A., Mognaschi, E., Rigamonti, A., Tognetti, V., Verrucchi, P.
The correlated spin dynamics and the temperature dependence of the correlation length $\xi(T)$ in two-dimensional quantum ($S=1/2$) Heisenberg antiferromagnets (2DQHAF) on square lattice are discussed in the light of experimental results of proton sp
Externí odkaz:
http://arxiv.org/abs/cond-mat/9903450
Publikováno v:
Phys. Rev. B 60, 7299 (1999)
The classical XXZ triangular-lattice antiferromagnet (TAF) shows both an Ising and a BKT transition, related to the chirality and the in-plane spin components, respectively. In this paper the quantum effects on the thermodynamic quantities are evalua
Externí odkaz:
http://arxiv.org/abs/cond-mat/9902024
Publikováno v:
Phys. Rev. E 60, 231 (1999)
We consider quantum nonlinear many-body systems with dissipation described within the Caldeira-Leggett model, i.e., by a nonlocal action in the path integral for the density matrix. Approximate classical-like formulas for thermodynamic quantities are
Externí odkaz:
http://arxiv.org/abs/cond-mat/9901265
Publikováno v:
Physica A 271, 387 (1999)
The pure-quantum self-consistent harmonic approximation (PQSCHA) permits to study a quantum system by means of an effective classical Hamiltonian - depending on quantum coupling and temperature - and classical-like expressions for the averages of obs
Externí odkaz:
http://arxiv.org/abs/cond-mat/9812050
The pure-quantum self-consistent harmonic approximation, a semiclassical method based on the path-integral formulation of quantum statistical mechanics, is applied to the study of the thermodynamic behaviour of the quantum Heisenberg antiferromagnet
Externí odkaz:
http://arxiv.org/abs/cond-mat/9812041
Publikováno v:
in "Path Integrals from peV to TeV - 50 Years from Feynman's paper", eds. R.Casalbuoni et al. (World Scientific, Singapore, 1999), pag. 160
We consider quantum nonlinear systems with dissipation described within the Caldeira-Leggett model, i.e., by a nonlocal action in the path integral for the density matrix. Approximate classical-like formulas are derived in order to evaluate thermal a
Externí odkaz:
http://arxiv.org/abs/cond-mat/9811357