Distorted diamond Ising-Hubbard chain

The ground state and thermodynamics of distorted Ising-Hubbard chains are studied with on-site Coulomb repulsion taken into account. A decoration-iteration transformation method is used to obtain exact results for the free energy, entropy, specific heat, magnetization of the Ising and Hubbard subsystems, and magnetic susceptibility. The effect of Coulomb repulsion on the ground state, field and temperature dependences of the magnetization, magnetic susceptibility, and specific heat is studied for the case of a geometrically frustrated system. Strong repulsion leads to formation of an additional high-temperature peak in the specific heat. Independently of any repulsion, the temperature dependence of the specific heat can have two low-temperature peaks. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3592221]