Speaker: Saheli Sarkar - Brookhaven National Laboratory, USA
Abstract: As an example of quantum criticality on a compressible lattice we study the Lorentz invariant Φ4 theory with an N-component field Φ, where strain couples to the square of the order parameter. In three spatial dimensions this coupling as well as the self-interaction of the Φ field are both marginal on the tree-level. We compute the one-loop re-normalization group equations treating the Φ field as well as the phonons on the same footing. We find that the velocities of the Φ field as well as of the phonons are re-normalized yielding an effective dynamical exponent Z 1. The re-normalization group flow is found to depend on the number of components N. Whereas we find run-away flow for N 4 a new fixed-point emerges for N = 4. We discuss the relation to known results for classical criticality. Our findings are directly relevant to insulating quantum critical anti-ferromagnets.