Transport and interaction blockade of cold bosonic atoms in a triple-well potential

We investigate the transport properties of cold bosonic atoms in a triple-well potential that consists of two large outer wells, which act as microscopic source and drain reservoirs, and a small inner well, which represents a quantum-dot-like scattering region. Such configurations can be realized by optical triple-well lattices generalizing the setup realized in the interaction blockade experiment by Cheinet et al. [Phys. Rev. Lett. 101, 090404 (2008)]. Bias and gate "voltages" are introduced in order, respectively, to tilt the triple-well configuration and to shift the energetic level of the inner well with respect to the outer ones. By means of exact diagonalization considering a total number of 6 atoms in the triple-well potential, we find diamond-like structures for the occurrence of single-atom transport in the parameter space spanned by the bias and gate voltages, in close analogy with the Coulomb blockade in electronic quantum dots. We demonstrate how one can infer the interaction energy in the central well from the distance between the diamonds, and discuss the possibility of realizing single-atom pumping across the quantum dot.