COULOMB-BLOCKADE ELECTROMETER WITH A HIGH-T-C ISLAND

We report on a successful attempt to fabricate a Coulomb blockade elec trometer consisting of an ultrasmall YBa2Cu3O7-delta(YBCO) island coup led to two gold electrodes through a high-resistance native surface tu nnel barrier. A third electrode placed near the island was used as an electrostatic gate, Spectra typical for tunneling into the YBCO superc onductor were reproducibly measured, At temperatures below 0.5 K the l ow-bias conductance was suppressed by the Coulomb blockade. The blocka de could be periodically varied by the gate potential. An external mag netic field of up to 5 T strongly influenced the transport via the isl and but without any change in the period of the Coulomb oscillations. (C) 1996 American Institute of Physics.