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Title: Why the superfluid density collapses in overdoped cuprates
Plain: Adding holes beyond the optimum lowers the superconducting temperature, and the density of paired electrons falls in step even though the metal looks more ordinary; disorder and new physics are both proposed as the cause.
Precise: In overdoped La2-xSrxCuO4 films the zero-temperature phase stiffness rho_s0 is proportional to $T_c$ and far below the BCS value expected from the normal-state Drude weight (2016). Determine whether d-wave BCS theory with realistic (forward and point) disorder accounts quantitatively for rho_s0(p), the T-linear $\rho_s(T)$, and the residual uncondensed Drude weight seen in terahertz optics, or whether intrinsic inhomogeneity or a different pairing state is required.
Settled by: Optical, penetration-depth and tunneling data on the same overdoped films compared with disorder-averaged Bogoliubov-de Gennes calculations using independently measured scattering rates.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: contested
Status note: Dirty d-wave calculations (2017 onward) reproduce several trends, while optical data showing a large uncondensed fraction are cited against them.
Posed since: 2016