Mott-insulator mediated Josephson physics

Sindhunil Barman Roy

Alwyn C. Scott

Smitha Vishveshwara, Courtney Lannert

We investigate the static and dynamic properties of bosonic lattice systems in which condensed and Mott insulating phases coexist due to the presence of a spatially varying potential. We formulate a description of these inhomogeneous systems and calculate the bulk energy at and near equilibrium. We derive the explicit form of the Josephson coupling between disjoint superfluid regions separated by Mott insulating regions. We obtain detailed estimates for the case of alternating superfluid and Mott insulating spherical shells in a radially symmetric parabolically confined cold atom system.

P. Donohue, Thierry Giamarchi

We show that in a commensurate bosonic ladder, a quantum phase transition occurs between a Mott insulator and a superfluid when interchain hopping increases. We analyze the properties of this transition as well as the physical properties of the two phases. We discuss the physical consequences for experimental systems such as Josephson Junction arrays.

Sanjeev Kumar, Vikram Tripathi

We study the current response of an ac-driven dissipative Mott-insulator system, a normal quantum dot array, using an analytical Keldysh field-theory approach. Deep in the Mott-insulator regime, the nonequilibrium steady state (NESS) response resembles a resistively shunted Josephson array with a nonequilibrium Mott-insulating to conductor transition as the drive frequency $\mathrm{\ensuremath{\Omega}}$ is increased. The diamagnetic component of the NESS in the conducting phase is anomalous, implying negative inductance, strikingly reminiscent of the $\ensuremath{\eta}$-pairing phase of a Josephson array with negative phase stiffness. However, in the presence of an additional dc field the signature of supercurrent---Shapiro steps---is completely absent. We interpret these properties as number-phase fluctuation effects shared with Josephson systems rather than superconductivity.