Physical review. B./Physical review. B
Bose metal in an exactly solvable model with infinite-range Hatsugai-Kohmoto interaction
Wei-Wei Yang, Hong‐Gang Luo, Yin Zhong
Abstract
In a conventional boson system, the ground state can either be an insulator or a superfluid (SF) due to the duality between particle number and phase. This paper reveals that the long-sought Bose metal (BM) state can be realized in an exactly solvable interacting bosonic model, i.e., the Bose-Hatsugai-Kohmoto (BHK) model, which acts as the nontrivial extension of Bose-Hubbard (BH) model. By tuning the parameters such as bandwidth $W$, chemical potential $\ensuremath{\mu}$, and interaction strength $U$, a BM state without any symmetry breaking can be accessed for a generic $W/U$ ratio, while a Mott insulator (MI) with integer boson density is observed at small $W/U$. The quantum phase transition between the MI and BM states belongs to the universality class of the Lifshitz transition, which is further confirmed by analyzing the momentum-distribution function, the Drude weight, and the SF weight. Additionally, our investigation at finite temperature reveals similarities between the BM state and the Fermi liquid, such as a linear-$T$ dependent heat capacity ($Cv\ensuremath{\sim}\ensuremath{\gamma}T$) and a saturated charge susceptibility (${\ensuremath{\chi}}_{c}\ensuremath{\sim}$ constant) as $T$ approaches zero. Comparing the BM state with the SF state in the standard BH model, we find that the key feature of the BM state is a compressible total wavefunction accompanied by an incompressible zero-momentum component. Given that the BM state prevails over the SF state at any finite $U$ in the BHK model, our paper suggests the possibility of realizing the BM state with on-site repulsion interactions in momentum space.