2018/10/31 by Saurabh Maiti, Tigran Sedrakyan, Tigran A. Sedrakyan · 27 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Bose–Einstein condensate #Boson #Condensed matter physics #Degenerate energy levels #Frustration #Ground state #Lattice (music) #Mathematical physics #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Reciprocal lattice #Topological Materials and Phenomena #Wave function #cond-mat.quant-gas #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.99.174418
published in Physical review. B./Physical review. B 99(17) (American Physical Society) · 11 pages, Revtex, 6 figures
openalex publication_date 2019/05/20 · arxiv created 2019/06/28 · arxiv updated 2019/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Strongly interacting bosons that live in a lattice with degeneracy in its lowest-energy band experience frustration that can prevent the formation of a Bose-Einstein condensate. Such systems form an ideal playground to investigate spin-liquid behavior. We use the variational principle and the Chern-Simons technique of fermionization of hard-core bosons on the kagome lattice to find that below lattice filling fraction \ensuremathν=(1)/(3) the system favors a topologically ordered chiral spin-liquid state that is gapped in bulk, spontaneously breaks time-reversal symmetry, and supports massless chiral bosonic edge mode. We construct the many-body variational wave function of the state and show that the corresponding energy coincides with the energy of the flat band. This result proves that the ground state of the system cannot stabilize a Bose condensate below \ensuremathν=(1)/(3). The fermionization and variational scheme we outline apply to any non-Bravais lattice. We distinguish between the roles played by the Chern-Simons gauge field in lattices with a flat band and those exhibiting a moatlike dispersion (which is degenerate along a closed contour in the reciprocal space). We also suggest experimental probes to differentiate the proposed ground state from a condensate.