Session A9: Superconductivity: Thermodynamic and Doping Effects

8:00 AM–11:00 AM, Monday, March 5, 2007
Colorado Convention Center Room: Korbel 1D

Sponsoring Unit: DMP
Chair: Carmen Almasan, Kent State University

Abstract ID: BAPS.2007.MAR.A9.3

Abstract: A9.00003 : Magnetic Penetration Depth in Overdoped Tl-2201 Superconductors

8:48 AM–9:00 AM

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Authors:

  Jess H. Brewer
    (Univ. of British Columbia)

  Scott Stubbs
    (Univ. of British Columbia)

  Darren Peets
    (Univ. of British Columbia)

  Ruixing Liang
    (Univ. of British Columbia)

  Walter Hardy
    (Univ. of British Columbia)

  Doug Bonn
    (Univ. of British Columbia)

  Peter Russo
    (TRIUMF)

  Jeff Sonier
    (Simon Fraser Univ.)

Studies of the magnetic penetration depth $\lambda_{ab}$ {\it via\/} the $\mu^+$SR lineshape in the vortex state has revealed a great deal about {\sl under\/}doped cuprate superconductors, including the original confirmation of $d$-wave superconductivity. However, {\sl over\/}doped cuprates have been neglected, partly due to the difficulty of doping sufficiently to decrease $T_c$, and partly because the overdoped materials are thought to be ``ordinary Fermi liquid'' superconductors, about which many presume we already know everything. In the belief that we may {\sl not\/} know everything about these materials, the UBC group has set out to grow high quality crystals of Tl$_2$Ba$_2$CuO$_{6+\delta}$ (Tl-2201), which can be made {\sl very\/} overdoped, to the point of $T_c \to 0$. We have now used $\mu^+$SR lineshape studies to measure $\lambda_{ab}$ as a function of $T$ and $H$ for crystal mosaics with $T_c$'s of 72, 60 and 46 K. As expected, $\lambda_{ab}^{-2}(T=0)$ continues to increase with doping beyond optimal doping, but then decreases again with higher doping. We also find a strong dependence on the applied field $H$. The low-$T$ behavior of $\lambda_{ab}^{-2}(T)$ is again strongly linear, as expected for a $d$-wave superconductor.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2007.MAR.A9.3