Finite Temperature Properties of KTaO$_3$ Thin Films from First-Principles

Thin films made of the incipient ferroelectric KTaO$_3$ are studied using a parameterized effective Hamiltonian, $H_{\rm eff}$. Quantum effects are turned off and on by performing classical Monte Carlo and, path integral quantum Monte Carlo simulations respectively. The films are simulated to be grown along the [001] pseudo-cubic direction. Different electrical and mechanical boundary conditions are investigated. Particular striking predictions are (1) that, unlike in the bulk, quantum effects are unable to suppress ferroelectricity in KTaO$_3$ thin films and, (2) the formation of complex ferroelectric nanodomains, depending on the boundary conditions.\\ This work is supported by ONR grants N 00014-01-1-0365, N 00014-04-1-0413 and N 00014-01-1-0600 and NSF grants DMR-9983678 and DMR-0404335