103
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      A Mott insulator of fermionic atoms in an optical lattice

      Preprint

      Read this article at

          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          In a solid material strong interactions between the electrons can lead to surprising properties. A prime example is the Mott insulator, where the suppression of conductivity is a result of interactions and not the consequence of a filled Bloch band. The proximity to the Mott insulating phase in fermionic systems is the origin for many intriguing phenomena in condensed matter physics, most notably high-temperature superconductivity. Therefore it is highly desirable to use the novel experimental tools developed in atomic physics to access this regime. Indeed, the Hubbard model, which encompasses the essential physics of the Mott insulator, also applies to quantum gases trapped in an optical lattice. However, the Mott insulating regime has so far been reached only with a gas of bosons, lacking the rich and peculiar nature of fermions. Here we report on the formation of a Mott insulator of a repulsively interacting two-component Fermi gas in an optical lattice. It is signalled by three features: a drastic suppression of doubly occupied lattice sites, a strong reduction of the compressibility inferred from the response of double occupancy to atom number increase, and the appearance of a gapped mode in the excitation spectrum. Direct control of the interaction strength allows us to compare the Mott insulating and the non-interacting regime without changing tunnel-coupling or confinement. Our results pave the way for further studies of the Mott insulator, including spin ordering and ultimately the question of d-wave superfluidity.

          Related collections

          Most cited references2

          • Record: found
          • Abstract: not found
          • Article: not found

          Single-Particle Excitations in Magnetic Insulators

            Bookmark
            • Record: found
            • Abstract: found
            • Article: found
            Is Open Access

            Evidence for Superfluidity of Ultracold Fermions in an Optical Lattice

            The study of superfluid fermion pairs in a periodic potential has important ramifications for understanding superconductivity in crystalline materials. Using cold atomic gases, various condensed matter models can be studied in a highly controllable environment. Weakly repulsive fermions in an optical lattice could undergo d-wave pairing at low temperatures, a possible mechanism for high temperature superconductivity in the cuprates. The lattice potential could also strongly increase the critical temperature for s-wave superfluidity. Recent experimental advances in the bulk include the observation of fermion pair condensates and high-temperature superfluidity. Experiments with fermions and bosonic bound pairs in optical lattices have been reported, but have not yet addressed superfluid behavior. Here we show that when a condensate of fermionic atom pairs was released from an optical lattice, distinct interference peaks appear, implying long range order, a property of a superfluid. Conceptually, this implies that strong s-wave pairing and superfluidity have now been established in a lattice potential, where the transport of atoms occurs by quantum mechanical tunneling and not by simple propagation. These observations were made for unitarity limited interactions on both sides of a Feshbach resonance. For larger lattice depths, the coherence was lost in a reversible manner, possibly due to a superfluid to insulator transition. Such strongly interacting fermions in an optical lattice can be used to study a new class of Hamiltonians with interband and atom-molecule couplings.
              Bookmark

              Author and article information

              Journal
              2008-04-24
              2010-01-21
              Article
              10.1038/nature07244
              0804.4009
              17317f8c-8058-4f78-a5fb-2ed7b5247afd

              http://arxiv.org/licenses/nonexclusive-distrib/1.0/

              History
              Custom metadata
              Nature (London) 455, 204-207 (2008)
              6 pages, 4 figures
              cond-mat.other cond-mat.str-el

              Condensed matter
              Condensed matter

              Comments

              Comment on this article