Exact Diagonalization Study of an Extended Hubbard Model for a Cubic Cluster at Quarter Filling |

K. Szałowski
^{a}, T. Balcerzak^{ a}, M. Jaščur^{ b}, A. Bobák^{ b} and M. Žukovič^{ b}^{a}Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of Łódź, Pomorska 149/153, PL-90236 Łódź, Poland
^{b}Department of Theoretical Physics and Astrophysics, Faculty of Sciences, P.J. Šafárik University, Park Angelinum 9, 041 54 Košice, Slovakia |

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In the paper the thermodynamics of a cubic cluster with 8 sites at quarter filling is characterized by means of exact diagonalization technique. Particular emphasis is put on the behaviour of such response functions as specific heat and magnetic susceptibility. The system is modelled with extended Hubbard model which includes electron hopping between both first and second nearest neighbours as well as Coulombic interactions, both on-site and between nearest-neighbour sites. The importance of hopping between second nearest neighbours and Coulombic interactions between nearest neighbours for the temperature dependences of thermodynamic response functions is analysed. In particular, the predictions of the Schottky model are compared with the calculations based on the full energy spectrum. |

DOI: 10.12693/APhysPolA.131.1012 PACS numbers: 75.40.Cx, 75.75.-c, 75.10.Lp, 71.27.+a, 65.80.-g, 05.70.Ce |