Analysis of Mott insulator transition for ultracold atomic system in optical lattice

Scott N. Sanders, Florian Mintert, Eric J. Heller

We study matter-wave scattering from an ultracold, many-body atomic system trapped in an optical lattice. The angular cross section of the target lattice for a matter wave is determined and is demonstrated to have a strong dependence on the many-body phase, superfluid, or Mott insulator. Analytical approaches are employed deep in the superfluid and Mott-insulator regimes, while intermediate points in the phase transition are treated numerically. Matter-wave scattering offers a convenient method for nondestructively probing the quantum many-body phase transition of atoms in an optical lattice.

N. Dupuis, K. Sengupta

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.

Sebastiano Pilati, Ping Nang Ma, Xi Dai +1 more

K. Sengupta, N. Dupuis

We study the phase diagram of ultracold bosons in an optical lattice near a Feshbach resonance. Depending on the boson density, the strength of the optical-lattice potential and the detuning from resonance, the ground state can be a Mott insulator, a superfluid phase with both an atomic and a molecular condensate, or a superfluid phase with only a molecular condensate. Mott insulator to superfluid transitions can be induced either by decreasing the strength of the optical-lattice potential or by varying the detuning from the Feshbach resonance. Quite generally, we find that for a commensurate density the ground state may undergo several insulator-superfluid or superfluid-insulator transitions as the magnetic field is varied through the resonance.

Nikolay V. Prokof'ev