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Quasiparticle mass enhancement approaching optimal doping in a high-Tc superconductor

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Science  26 Mar 2015:
aaa4990
DOI: 10.1126/science.aaa4990

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Abstract

In the quest for superconductors with higher transition temperatures

(Tc), one emerging motif is that electronic interactions favorable for superconductivity can be enhanced by fluctuations of a broken-symmetry phase. Recent experiments have suggested the existence of the requisite broken symmetry phase in the high-Tc cuprates, but the impact of such a phase on the ground-state electronic interactions has remained unclear. We use magnetic fields exceeding 90 tesla to access the underlying metallic state of the cuprate YBa2Cu3O6+δ over a wide range of doping, and observe magnetic quantum oscillations that reveal a strong enhancement of the quasiparticle effective mass toward optimal doping. This mass enhancement results from increasing electronic interactions approaching optimal doping, and suggests a quantum-critical point at a hole doping of pcrit ≈ 0.18.

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