Coulomb blockade electrometer based on single Cooper pair tunneling

Zorin, A.B. and Pashkin, Yu.A. and Krupenin, V.A. and Scherer, H. (1998) Coulomb blockade electrometer based on single Cooper pair tunneling. Applied Superconductivity, 6 (7). pp. 453-458. ISSN 0964-1807

Abstract

We have studied the electrometric characteristics of the Bloch transistor, i.e. the structure comprising a double small-capacitance superconductor junction (where both the Josephson and the charging energies, EJ1,2∽EC1,2≫kBT) and an adjacent gate electrode polarizing its island. The transistor bias is realized through small-sized high-ohmic resistors (≫RQ=h/4e2≈6.5 kΩ) to ensure a high electromagnetic impedance of the transistor environment. At low bias current, a coherent flow of single Cooper pairs occurs and the average voltage across the transistor shows a 2e-periodic dependence on the polarization charge Q0. The sensitivity of such an electrometer has been evaluated and found to be comparable to that of the single-electron counterpart. The device has been fabricated with Al/AlOx/Al junctions and two miniature on-chip Cr resistors (each of 80 kΩ and 10μm long) which were located very close to the junctions. We used this device to measure 1/f noise of the background charge and found it to be about 9×10−4e/Hz1/2 at 10Hz.