Quantum effects in ann-component vector model for structural phase transitions

The influence of quantum effects on the critical properties of an $n$-component vector model for structural phase transitions is explored. It is shown for $n=1,2, \mathrm{and} \infty$ that these effects can suppress the occurrence of a phase transition for all dimensions $d$. This turns out to be of particular relevance for systems where the classical transition temperature almost vanishes ($T_c=0\mathrm{}$ represents the displacive limit). We also discuss the critical properties at this limit for $n=\infty$ and show that the critical exponents change discontinously.