# Quantum Critical Point Shifts under Superconductivity: the Pnictides and the Cuprates

 Title: Quantum Critical Point Shifts under Superconductivity: the Pnictides and the Cuprates Author: Moon, Eun; Sachdev, Subir Note: Order does not necessarily reflect citation order of authors. Citation: Moon, Eun, and Subir Sachdev. 2010. Quantum critical point shifts under superconductivity: the pnictides and the cuprates. Physical Review B 82(10): 104516. Full Text & Related Files: 1005.3312v4.pdf (552.6Kb; PDF) Abstract: We compare the position of an ordering transition in a metal to that in a superconductor. For the spin-density wave (SDW) transition, we find that the quantum critical point shifts by order $$\mid\Delta\mid$$, where $$\Delta$$ is pairing amplitude so that the region of SDW order is smaller in the superconductor than in the metal. This shift is larger than the $$\sim\mid\Delta\mid$$ shift predicted by theories of competing orders which ignore Fermi-surface effects. For Ising-nematic order, the shift from Fermi-surface effects remains of order $$\mid\Delta\mid 2$$. We discuss implications of these results for the phase diagrams of the cuprates and the pnictides. We conclude that recent observations imply that the Ising-nematic order is tied to the square of the SDW order in the pnictides but not in the cuprates. Published Version: doi://10.1103/PhysRevB.82.104516 Other Sources: http://arxiv.org/abs/1005.3312v4 Terms of Use: This article is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#OAP Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:7615608 Downloads of this work: