Electrocaloric effect in cubic Hubbard nanoclusters

Abstract

In the paper a computational study of the electrocaloric efect is presented for a cubic nanocluster consisting of 8 sites. The system of interest is described by means of an extended Hubbard model in external electric feld at half flling of the energy levels. The thermodynamic description is obtained within canonical ensemble formalism on the basis of exact numerical diagonalization of the system Hamiltonian. In particular, the entropy and the specifc heat are determined as a function of temperature and external electric feld. The electrocaloric efect is described quantitatively by isothermal entropy change. The behaviour of this quantity is thoroughly analysed as a function of extended Hubbard model parameters, temperature and electric feld variation magnitude. The existence of direct and inverse electrocaloric efect is predicted for some range of model parameters. A high sensitivity to Hubbard model parameters is shown, what paves the way towards controlling and tuning the efect. A non-linear, quadratic dependence of isothermal entropy change on electric feld variation magnitude is demonstrated. The potential for applications of electrocaloric efect in strongly correlated nanoclusters is shown.