d-wave YBCO Josephson junctions in the quantum phase and charge limit
Chalmers University of Technology, Göteborg
Tuesday, 10 February 2009, 15:15
Seminar room F
We present direct observation of macroscopic quantum properties in an all high
critical temperature superconductor (HTS) d-wave Josephson junction. Although
dissipation caused by low energy excitations is expected to strongly suppress
quantum effects we demonstrate macroscopic quantum tunneling  and energy level
quantization  in our d-wave Josephson junction.
The results clearly indicate that the role of dissipation mechanisms in high
temperature superconductors has to be revised, and may also have consequences for
a new class of solid state "quiet" quantum bit with superior coherence time.
Moreover we realized for the first time an all-HTS single electron tunneling
transistor. This device is a powerful tool to probe the quasiparticle spectrum in
HTS materials and should give valuable information about dissipation processes in
HTS based quantum circuits.
 T. Bauch et al., Phys. Rev. Lett. 94, 087003 (2005).
 T. Bauch et al, Science 311, 57 (2006).