We investigate the functional form of the order-parameter (two-point) correlation function in quantum critical phenomena. When broken particle-hole symmetry brings the dynamical critical exponent $z=2$, we find that the equal-time correlation function at criticality does not display a diverging correlation length. We illustrate our conclusions by Monte Carlo calculations of the quantum rotor model in $d=2$ space dimensions.

• Received 25 September 2007

DOI:https://doi.org/10.1103/PhysRevB.77.165124