Trapping centers at the superfluid-Mott-insulator criticality: Transition between charge-quantized states.

Under the conditions of superfluid-Mott-insulator criticality in two dimensions, the trapping centers--i.e., local potential wells and bumps--are generically characterized by an integer charge corresponding to the number of trapped particles (if positive) or holes (if negative). Varying the strength of the center leads to a transition between two competing ground states with charges differing by ±1. The hallmark of the transition scenario is a splitting of the number density distortion δn(r) into a half-integer core and a large halo carrying a complementary charge of ±1/2. The sign of the halo changes across the transition and the radius of the halo r0 diverges on the approach to the critical strength of the center, V=Vc, by the law r0 ∝ |V−Vc|−˜ν, with ˜ν ≈ 2.33(5). [ABSTRACT FROM AUTHOR]