Exotic Gapless Mott Insulators of Bosons on Multileg Ladders
We present evidence for an exotic gapless insulating phase of hard-core bosons on multileg ladders with a density commensurate with the number of legs. In particular, we study in detail a model of bosons moving with direct hopping and frustrating ring exchange on a 3-leg ladder at ν=1/3 filling. For sufficiently large ring exchange, the system is insulating along the ladder but has two gapless modes and power law transverse density correlations at incommensurate wave vectors. We propose a determinantal wave function for this phase and find excellent comparison between variational Monte Carlo and density matrix renormalization group calculations on the model Hamiltonian, thus providing strong evidence for the existence of this exotic phase. Finally, we discuss extensions of our results to other N-leg systems and to N-layer two-dimensional structures.
Additional Information© 2011 American Physical Society. Received 28 August 2010; published 27 January 2011. This work was supported by the NSF under Grants No. DMR-0529399 (M. S. B., R.V. M., and M. P. A. F.) and No. DMR-0907145 (O. I. M.); the DOE under Grant No. DE-FG02-06ER46305 (D. N. S.); and Microsoft Station Q (R.V. M. and R. K. K.).
Published - Block2011p12682Phys_Rev_Lett.pdf