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Scaling of superconducting gap and critical temperature in doped Bi-2212, Bi-2201 and Hg-1201

Yaroslav G. Ponomarev ,  Svetoslav Kuzmichev ,  Mikhail Mikheev ,  Marina Sudakova ,  Sergeii Tchesnokov 

M.V. Lomonosov Moscow State University, Vorobyevy gory, Moscow 119992, Russian Federation


High-temperature superconductivity in cuprates occurs in CuO2 planes within a relatively narrow interval of impurity hole concentration p [1]. It is well established that the transition temperature Tc varies with p according to a parabolic law. At the same time there is a conflicting information about a doping dependence of a superconducting gap Δ. In the present investigation we have measured Δ in doped Bi-2212, Bi-2201 and Hg-1201 by tunneling, Josephson and Andreev spectroscopy using a break junction technique. In particular we have studied the intrinsic Josephson effect (IJE) on natural ultrathin steps (with a height from 1.5 to 30 nm) which are always present on cryogenically cleaved surfaces of doped HTSC single crystals. For a stack of n equivalent junctions the value of the gap voltage Vgn corresponding to a sharp increase of a quasi-particle current (J||c) is given by: Vgn = (2Δ/e)n. The experimental dependence Vgn(n) has been used to determine the gap parameter Δ with high accuracy. The unusual sharpness of a gap feature in case of a highly anisotropic gap parameter could be caused by an extended van Hove singularity [1], the presence of which significantly enhances the gap structure in current-voltage characteristics for J||c [2, 3]. We have used the data of tunneling, intrinsic tunneling and Andreev spectroscopies to derive the dependence of the superconducting gap Δ on the impurity hole concentration p in Bi-2212, Bi-2201 and Hg-1201. In all cases the superconducting gap Δ(4.2 K) was found to scale with the transition temperature Tc in the entire doping range.

1. A.A. Abrikosov, Physica C 341-348, 97 (2000).
2. J.Y.T. Wei et al., Phys. Rev. B 57, 3650 (1998).
3. P.I. Arseev et al., cond-mat/0304525.


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Presentation: Poster at E-MRS Fall Meeting 2006, Symposium K, by Yaroslav G. Ponomarev
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 11:50
Revised:   2009-06-07 00:44