Electrocaloric effect in cubic Hubbard nanoclusters

In the paper a computational study of the electrocaloric effect 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 field at half filling 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 specific heat are determined as a function of temperature and external electric field. The electrocaloric effect 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 field variation magnitude. The existence of direct and inverse electrocaloric effect 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 effect. A non-linear, quadratic dependence of isothermal entropy change on electric field variation magnitude is demonstrated. The potential for applications of electrocaloric effect in strongly correlated nanoclusters is shown.