Lattice Effects on Nematic Quantum Criticality in Metals.

Theoretically, it is commonly held that in metals near a nematic quantum critical point the electronic excitations become incoherent on the entire "hot" Fermi surface, triggering non-Fermi-liquid behavior. However, such conclusions are based on electron-only theories, ignoring a symmetry-allowed coupling between the electronic nematic variable and a suitable crystalline lattice strain. Here, we show that including this coupling leads to entirely different conclusions because the critical fluctuations are mostly cut off by the noncritical lattice shear modes. At sufficiently low temperatures the thermodynamics remain Fermi-liquid type, while, depending on the Fermi surface geometry, either the entire Fermi surface stays cold, or at most there are hot spots. In particular, our predictions are relevant for the iron-based superconductors.