Quantum phase transitions in the matrix product states of the one-dimensional boson Hubbard model

Abstract

We study quantum phase transitions in the matrix product states of the one-dimensional boson Hubbard model, whose amount of entanglement is limited by the size of the matrices used in the representation of the states. By measuring entanglement entropy and other physical properties, we observe that the Mott-insulator-to-superfluid transitions occur sharp and continuous, accompanied by shifting transition points that are not blurred by finite entanglement effects. This strongly suggests that the transition always occurs between the Mott insulator and a mean-field-like compressible state, followed by the more entangled superfluid state. Both $O(2)$ and the commensurate-incommensurate transitions are studied, whose properties can be characterized by entanglement spectra and critical exponents.