Disorder-induced quantum phenomena in inhomogeneous optical lattices

Pinaki Sengupta, Aditya Raghavan, Stephan Haas

Matthew C. Beeler, E.E. Edwards, Tao Hong +1 more

Vera Guarrera, L. Fallani, Jessica Lye +2 more

In recent years ultracold atoms in optical lattices have been extensively employed as quantum simulators to study the physics of conventional solid state systems. Due to the possibility of introducing controlled disorder, it appears now a straightforward progression to use ultracold atoms in optical potentials to also study the physics of complex systems. We experimentally study a system of bosonic 87Rb atoms in a 3D optical lattice, where disorder is introduced on the length scale of the lattice sites by using an auxiliary optical lattice with a non‐commensurate wavelength. Increasing the amount of disorder, we observe the transition from a Mott Insulator state to a novel gapless insulating phase induced by the cooperation of interactions and disorder, which could be identified with a Bose Glass phase. We discuss the experimental results as well as possible additional techniques for a better diagnostic of the system and future implementations of the two‐color lattices in the study of different disorder‐induced phenomena.

Francesco Paolo Mancini, Pasquale Sodano, Andrea Trombettoni

The spontaneous emergence of enhanced responses and local orders are properties often associated with complex matter where nonlinearities and spatial inhomogeneities dominate. We discuss these phenomena in quantum devices realized with superconducting Josephson junction networks and cold atoms in optical lattices. We evidence how the pertinent engineering of the network's shape induces the enhancement of the zero-voltage Josephson critical currents in superconducting arrays as well as the emergence of spatially localized condensates for cold atoms in inhomogeneous optical lattices.

Matthew C. Beeler, E.E. Edwards, Tao Hong +1 more

S. Drenkelforth, G. Kleine Büning, J. Will +5 more

We investigate both experimentally and theoretically disorder- induced damping of Bloch oscillations of Bose–Einstein condensates in optical lattices. The spatially inhomogeneous force responsible for the damping is realized by a combination of a disordered optical and a magnetic gradient potential. We show that the inhomogeneity of this force results in a broadening of the quasimomentum spectrum, which in turn causes damping of the centre-of-mass oscillation. We quantitatively compare the obtained damping rates to the simulations using the Gross–Pitaevskii equation. Our results are relevant for high precision experiments on very small forces, which require the observation of a large number of oscillation cycles.