State Preparation and Dynamics of Ultracold Atoms in Higher Lattice Orbitals

Abstract

We report on the realization of a multi-orbital system with ultracold atoms in the excited bands of a 3D optical lattice by selectively controlling the band population along a given lattice direction. The lifetime of the atoms in the excited band is found to be considerably longer (10-100 times) than the characteristic time scale for inter-site tunneling, thus opening the path for orbital selective many-body physics with ultracold atoms. Upon exciting the atoms from an initial lowest band Mott insulating state to higher lying bands, we observe the dynamical emergence of coherence in 1D (and 2D), compatible with Bose-Einstein condensation to a non-zero momentum state.PACS numbers: 03.75. Lm, 03.75.Hh, 03.75.Nt Ultracold neutral atoms in optical lattices form a remarkable model system for investigations of strongly correlated quantum phases, highly relevant to modern solid state physics [1,2]. So far, experiments have mostly concentrated on strongly interacting atoms in the lowest energy band of an optical lattice. In solid state physics, however, orbital selective phenomena are known to play a crucial role for the description of topical materials with strong electronic correlations, such as the transitionmetal oxides exhibiting metal-insulator transitions, superconductivity and colossal magnetoresistance. The extension to excited Bloch bands with ultracold atoms in optical lattices allows to enter a regime beyond s-wave isotropy of the on-site atomic wave function on the one hand, and promises a novel route for the realization of long range interactions on the other hand. Recently, these aspects have attracted much attention and have lead to a series of predictions for novel e ects and quantum phases that could be realized with ultracold atoms in higher-lying orbitals. These include the generation of novel multi-avor and multi-orbital systems [3,4,5], supersolid quantum phases in cubic lattices [6,7], quantum stripe ordering in triangular lattices [8] or Wigner crystallization in honeycomb lattices [9]. An essential experimental question is however, how such systems could be prepared and whether they are stable.

Multiband bosons in optical lattices

“…Addressing the role of flavor dynamics and number fluctuation in different flavors requires probes which address different flavors individually. This has been demonstrated recently [10] by coupling atoms with Raman transitions between the lowest band and some excited band. In Ref.…”

“…This was experimentally demonstrated recently by Müller et al [10] by coupling atoms from the lowest band Mott insulator into the first excited p-band of the lattice via Raman transitions between bands. They found lifetimes of p-band atoms which were * Electronic address: jpjmarti@nordita.org considerably longer than the tunneling time-scale in the lattice and were also able to explore how coherence on the excited band was established.…”

“…In Ref. [10] the selectivity was achieved by breaking the degeneracy of p-band atoms by lattice anisotropy, but alternatively one could engineer a vanishing transition matrix elements for undesired transitions. Interestingly, Mueller et al [10] were also able to observe time-evolution of the Bose gas caused by flavor dynamics.…”

Chiral superfluidity with p-wave symmetry from an interacting s-wave atomic Fermi gas

“…Recently, the research of higher orbital bands in optical lattices has evolved rapidly 19 , where the orbital degrees of freedom are found to play a crucial role as in solid-state materials. From the early experimental attempt 20 to the breakthrough observation 21 of long-lived p-band bosonic atoms in a checkerboard lattice, a growing evidence points to an exotic p x þ ip y orbital Bose-Einstein condensate 19 . For fermions studied in this work, the decay from higher to lower bands is prevented by Pauli blocking, and the fermionic p-band system is even more robust than the bosonic counterpart.…”

Generation of robust entangled states in a non-Hermitian periodically driven two-band Bose-Hubbard system

“…Quite challenging in this respect are many-body models either in more dimensions [5][6][7] or with more modes per lattice site [8,9], extending e.g. single-band Hubbard models [10].…”