Thomas Lee Elifritz

http://arxiv.org/abs/1209.1571

Topological transitions of gapless paired states in mixed-geometry lattices, Dong-Hee Kim, Joel S. J. Lehikoinen and Päivi Törmä

Fermion pairing may coexist with magnetism in unconventional superconductors and nuclear matter, stabilized by non-BCS mechanisms. Remarkable sce- narios of exotic pairing with Fermi surfaces mismatched by chemical potential or mass difference have been suggested, inspiring experiments in solid-state materials and ultracold Fermi gases. Here we propose fermionic species to be confined in lattices of different geometry and show how such distortion of symmetry leads to unconventional quantum states. In particular, we consider pairing of one species in a graphene-like lattice with another in a triangular sublattice. We find a rich phase diagram of multiband pairing with gapped and gapless excitations at zero temperature, implying that gapless superfluids can be stabilized in these systems. Quantum phase transitions between topologically distinct phases are predicted. Realization of mixed-geometry systems, e.g. using spin-dependent optical lattices, provides a new dimension to the ultracold quantum simulator for exploring unconventional quantum states of matter.

U Ra

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