Number parity effects in the normal state of SrTiO3

We study the recently discovered even-odd effects in the normal state of single-electron devices manufactured at strontium titanium oxide/lanthanum aluminum oxide interfaces (STO/LAO). Within the framework of the number parity-projected formalism and a phenomenological fermion-boson model, we find that, in sharp contrast to conventional superconductors, the crossover temperature T* for the onset of number parity effect is considerably larger than the superconducting transition temperature Tc due to the existence of a pairing gap above Tc. Furthermore, the finite lifetime of the preformed pairs reduces by several orders of magnitude the effective number of states Neff available for the unpaired quasiparticle in the odd-parity state of the Coulomb blockaded STO/LAO island. Our findings are in qualitative agreement with the experimental results reported by Levy and coworkers for STO/LAO-based single electron devices.