Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 30: Superconductivity: Twenty Years High-T_c Cuprates - Recent Progress

TT 30.14: Vortrag

Donnerstag, 30. März 2006, 17:30–17:45, HSZ 02

Quasiparticle transport characteristics of thin film La_2−xCe_xCuO₄ bicrystal junction SQUIDs — •Michael Wagenknecht¹, Boris Chesca¹, Martin Mueller¹, Dieter Koelle¹, Reinhold Kleiner¹, Akio Tsukada², and Michio Naito³ — ¹Physikalisches Institut - Experimentalphysik II, Universitaet Tuebingen, Auf der Morgenstelle 14, 72076 Tuebingen — ²NTT Basic Research Laboratories, 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243, Japan — ³Department of Applied Physics, Tokyo University of Agriculture and Technology (TUAT) 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan

While it is widely recognized that hole doped cuprates have predominantly d-wave symmetry of the superconducting order parameter, for electron doped cuprates the issue remains controversial. Here we present quasiparticle transport measurements of electron doped La_2−xCe_xCuO₄ thin film bicrystal Josephson junction SQUIDs. The 900 nm thin films were deposited by molecular beam epitaxy on SrTiO₃ 24^∘ and 30^∘ [001]-tilt bicrystal substrates and have a Ce doping of x ∼ 0.08 and a T_c ∼ 30 K. At 4.2 K we observe in some SQUIDs a pronounced zero-bias anomaly in the quasiparticle differential conductance in magnetic fields up to 7 T, consistent with the formation of Andreev bound states at the junction interface. These results are strongly supportive of a d-wave symmetry, in accordance with previous work [1]. In addition we will discuss the subgap structures as well as some resonances at energies above the superconducting gap, which we repeatedly observed in quasiparticle transport measurements.

[1] B. Chesca et al., Phys. Rev. B 71, 104504 (2005).