Quantum critical point shifts under superconductivity: Pnictides and cuprates

Eun Gook Moon; Subir Sachdev

doi:10.1103/PhysRevB.82.104516

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Quantum critical point shifts under superconductivity: Pnictides and cuprates

Eun Gook Moon, Subir Sachdev

DOI 10.1103/PhysRevB.82.104516 · Physical Review B

T1

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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 |Δ|, where Δ 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 ∼|Δ|2 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 |Δ|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.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
La2-xSrxCuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown