Artykuły naukowe (WF)

Permanent URI for this collection

https://repozytorium.amu.edu.pl/handle/10593/63

Browse

Browsing Artykuły naukowe (WF) by Subject "charge-order"

Now showing 1 - 3 of 3
  • Item
    Electron phase separations involving superconductivity in the extended Hubbard models with pair hopping interaction
    (Polish Academy of Sciences, Institute of Physics, al. Lotników 32-46, PL-02-668 Warsaw, Poland, 2015-02) Kapcia, Konrad Jerzy
    In this work the extended Hubbard models with pair hopping interaction (at the atomic limit) are investigated within the variational approach, which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation (exact in $d\rightarrow+\infty$). We analyze mutual stability of the superconducting (SC) phase and charge (CO) or (ferro/antiferro-)magnetic (M) orderings as well as homogeneous mixed phases. Our preliminary results for U=0 show that the SC phase can coexist with the CO or M phases only in states with electron phase separation.
  • Item
    Some exact results for the zero-bandwidth extended Hubbard model with intersite charge and magnetic interactions
    (Polish Academy of Sciences, Institute of Physics, al. Lotników 32-46, PL-02-668 Warsaw, Poland, 2015-02) Kapcia, Konrad Jerzy; Kłobus, Waldemar; Robaszkiewicz, Stanisław
    The extended Hubbard model in the zero-bandwidth limit is studied. The effective Hamiltonian consists of (i) on-site U interaction and intersite (ii) 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) $U\rightarrow+\infty$ and n=1/2 ($W\neq 0$, $J\neq 0$). We obtain the exact formulas 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.
  • Item
    Superconductivity, charge orderings, magnetism, and their phase separations in the ground state of lattice models of superconductor with very short coherence length
    (Springer US, 233 Spring St, New York, NY 10013 USA, 2015-04) Kapcia, Konrad Jerzy
    We present the ground state results for lattice models of superconductor (SC) with extremely short coherence length, which also involve the interplay with charge (CO) and (anti-)ferromagnetic orderings. Our preliminary results at zero-temperature (derived by means of the variational approach which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation, exact in $d\rightarrow+\infty$), yields that the SC phase can coexist with the CO or magnetic (M) phases in states with electron phase separation (PS:SC/CO and PS:SC/M, respectively).