Quantum phase transition to unconventional multi-orbital superfluidity in optical lattices
By P. Soltan-Panahi, D. Lühmann, J. Struck, Patrick Windpassinger, Klaus Sengstock. Nature Physics, 2011
136 citations recorded by the source corpus.
The behaviour of molecules and solids is governed by the interplay of electronic orbitals. Superfluidity, in contrast, is typically considered a single-orbital effect. Now, a combined experimental and theoretical study provides evidence for a multi-orbital superfluid, with a complex order parameter, occurring in a binary spin mixture of atoms trapped in an hexagonal optical lattice. Orbital physics plays a significant role for a vast number of important phenomena in complex condensed-matter systems, including high-temperature superconductivity and unconventional magnetism. In contrast, phenomena in superfluids—in particular in ultracold quantum gases—are typically well described by the lowest orbital and a real order parameter1. Here, we report on the observation of a multi-orbital superfluid phase with a complex order parameter in binary spin mixtures. In this unconventional superfluid, the local phase angle of the complex order parameter is continuously twisted between neighbouring lattice sites. The nature of this twisted superfluid quantum phase is an interaction-induced admixture of the p-orbital contributions favoured by the graphene-like band structure of the hexagonal optical lattice used in the experiment. We observe a second-order quantum phase transition between the normal superfluid and the twisted superfluid phase, which is accompanied by a symmetry breaking in momentum space. The experimental results are consistent with calculated phase diagrams and reveal fundamentally new aspects of orbital superfluidity in quantum gas mixtures. Our studies might bridge the gap between conventional superfluidity and complex phenomena of orbital physics.
Subfields: Atomic and Molecular Physics, and Optics
View Paper: https://www.semanticscholar.org/paper/8ebbdb55b1cb39b52d89ce85462fa1f435c1559e
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In Atomic and Molecular Physics, and Optics
Citations in the corpus
- Creating, moving and merging Dirac points with a Fermi gas in a tunable honeycomb lattice (2011, methodology): “quantum gases, a honeycomb lattice has recently been realised and investigated with a Bose-Einstein condensate [16, 17], but no signatures of Dirac points were observed.”