Letter abstract


Nature Physics 3, 700 - 702 (2007)
Published online: 26 August 2007 | doi:10.1038/nphys707

Subject Categories: Condensed-matter physics | Materials physics

Quantum critical behaviour in the superfluid density of strongly underdoped ultrathin copper oxide films

Iulian Hetel, Thomas R. Lemberger & Mohit Randeria

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A central challenge in the physics of high-temperature superconductors is to understand superconductivity within a single copper oxide layer or bilayer, the fundamental structural unit, and how superconductivity is lost with underdoping of charge carriers. A seminal property of crystals and thick films1, 2, 3, 4 is that when mobile holes are removed from optimally doped CuO2 planes, the transition temperature, Tc, and superfluid density, ns(0), decrease in a surprisingly correlated fashion. We elucidate the essential physics of strongly underdoped bilayers by studying two-dimensional (2D) samples near the critical doping level where superconductivity disappears. We report measurements of ns(T) in films of Y1-xCaxBa2Cu3O7-delta as thin as two copper oxide bilayers with Tc values as low as 3 K. In addition to seeing the 2D Kosterlitz–Thouless–Berezinski transition5, 6 at Tc, we observe a remarkable scaling of Tc with ns(0), which indicates that the disappearance of superconductivity with underdoping is due to quantum fluctuations near a 2D quantum critical point.

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  1. Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA

Correspondence to: Thomas R. Lemberger e-mail: TRL@mps.ohio-state.edu

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