F. Pazmandi et Gt. Zimanyi, DIRECT MOTT INSULATOR TO SUPERFLUID TRANSITION IN THE PRESENCE OF DISORDER, Physical review. B, Condensed matter, 57(9), 1998, pp. 5044-5047
We use renormalization-group theory to examine the quantum phase trans
itions upon exiting the insulating phase of a disordered, strongly int
eracting boson system. For weak disorder we End a direct transition fr
om this Mott insulator to the superfluid phase. In d>4 a finite region
around the particle-hole symmetric point supports this direct transit
ion, whereas for 2 less than or equal to d<4 perturbative arguments su
ggest that the direct transition survives only precisely at commensura
te filling. For strong disorder the renormalization trajectories pass
next to two fixed points, describing a pair of distinct transitions; f
irst from the Mott insulator to the Bose glass, and then from the Bose
glass to the superfluid. The latter fixed point possesses statistical
particle-hole symmetry and a dynamical exponent z, equal to the dimen
sion d.