Katsuya Inagaki

Self-balancing resistance ratio bridge using a cryogenic current comparator

A cryogenic current comparator resistance bridge, developed to measure the resistance ratios of 1, 10, 100, and 6453.2 Omega against 1 Omega , is described. It is shown that the precision of the 1- Omega comparison is better than 0.01 p.p.m. This is attained by using an improved feedback system in the secondary current source. >

Quantized Hall resistance measurements

The quantized Hall resistances, R/sub H/(4), of Si MOSFETs were measured at approximately=0.5 K in a magnetic field of 15 T. The value of R/sub H/(4) was determined in terms of the Commonwealth Scientific and Industrial Research Organization (CSIRO) realization of the SI ohm. A weighted mean of three determinations gave a value for the quantity R/sub H/(4) of (6453.203,36(52)) Omega /sub SI-NML/ which can also be expressed as 6453.2(1.000,000,52(8)) Omega /sub SI-NML/. This R/sub H/(4) value gives a value for h/e/sup 2/ which is about 0.3 p.p.m. larger than the value for h/e/sup 2/ derived from the anomalous moment of the electron, using the quantum electrodynamics (QED) theory. >

Quantized hall and transverse resistivities in silicon MOS n-inversion layers

Abstract The results are reported of the quantized Hall and transverse resistivity measurements made on n-channel (100) inversion layers of Si-MOSFET devices at temperatures T = 1.6 to 0.5 K, magnetic fields H = 9.0 and 10.5 T for various excitation current densities. The Hall resistivity ϱxy is found to be integral fractions of h e 2 in precision better than 0.2 ppm over the concentration of electrons ieH hc = 1 × 10 12 to 3 × 1012/cm2 (i = 4, 8, 12) at the lowest temperatures. When the transverse resistivity ϱxx is finite in the Hall plateau regions, the deviation in ϱxy is roughly given by Δϱxy(i) = C·ϱminxx(i) where C ≌ −0.1 . This result is two orders of magnitude as large as that expected from existing theories.

Measurement System for Quantum Hall Effect Utilizing a Josephson Potentiometer

In order to improve the measurement accuracy of the quantum Hail effect, a new method has been developed utilizing a Josephson potentiometer and a Superconducting Quantum Interference Device (SQUID) galvanometer. A relative uncertainty of a few parts in 108 can be realized for the measurement of the ratio of the quantized Hall resistance to a reference resistor using this method.

An improved Josephson potentiometer system for the measurement of the quantum Hall effect

Several improvements have been made on a Josephson potentiometer and superconducting quantum interference device (SQUID) galvanometer system previously reported. Results of the measurement of the quantized Hall resistance obtained by the use of this system are in agreement with those obtained by means of a conventional potentiometer system to 0.02 ± 0.08 ppm for silicon-MOSFET samples. A comparison of the Hall resistance between two different quantized values corresponding to h/4e2 and h/8e2, for a sample, has been made without an uncertainty associated with the linearity of voltage-ratio measurements. A discussion is presented in relation to completeness of the quantization.

Quantized Hall Resistivity in Si-MOSFETs Measured at Liq. 3He Temperatures

The transverse and Hall resistivities of electrons in Si–MOS inversion layer have been measured at T ≃0.5 K in the magnetic fields H =9.0 T and 10.5 T, at the gate voltages around the transverse resistivity minima. The Hall resistivity is found to be integral fractions of h / e 2 in precision better than 2 parts in 10 7 over the concentration of electrons i e H / h c ranging from 1×10 12 cm -2 ( i =4) to 3×10 12 cm -2 ( i =12).

Energy Relaxation Process in n-Type InSb under Strong Longitudinal Magnetic Fields

The energy relaxation process in n -type InSb at liquid helium temperatures under the presence of strong longitudinal magnetic fields has been analysed taking into account the existence of an impurity band. The impurity band is found to act as a thermal reservoir of the conduction band electrons, which strongly affects the energy relaxation process. The observed saturation in the magnetic field dependence of the energy relaxation time is ascribed to the reduction of the rate of energy dissipation of conduction band electrons to the lattice, which arises from the interaction between electrons in the conduction and the impurity band.

Comparison of quantized Hall resistances R/sub H/(2) and R/sub H/(4) of a GaAs/AlGaAs heterostructure device

Quantized Hall resistances R/sub H/(4) and R/sub H/(2) of a GaAs/AlGaAs heterostructure were compared with reference resistors whose values are close to h/4e/sup 2/ or h/2e/sup 2/. The values of the reference resistors were compared with a 100 ohm standard resistor via a cryogenic current comparator (CCC) resistance bridge. Results showed that (4/spl times/R/sub H/(4)-2/spl times/R/sub H/(2))/2/spl times/R/sub H/(2)=(0.037/spl plusmn/0.019)/spl times/10/sup -6/. >

Supercurrent graduate in units of 2 ef

The supercurrent in the I-V characteristics of superconducting granular tin films are graduated in units of 2 ef, in the presence of microwave fields with f=8-12 GHz, to an accuracy of 200 p.p.m. This is interpreted in terms of the Bloch oscillations, which are demonstrated to be dual to the Josephson oscillations. When the measurement is carried out at extremely low temperatures using arrays of small Josephson junctions with well-controlled junction parameters, the accuracy can be improved by 3-4 orders of magnitude. Then it becomes possible to examine the consistency of three macroscopic quantum relations: nf=I/2e, V=mhf/2, and V/I=h/ie/sup 2/, where n, m, and i are integers. >

Observation of quantum hall effect in Si-MOSFET's by means of conventional and Josephson potentiometer systems

Measurements of the quantized Hall resistance <i>R</i>_H(<i>i</i>), <i>i</i>=4, 8, and 12, have been made for silicon metal-oxide semiconductor field-effect transistors under different experimental conditions <i>T</i>=0.5 to 1.4K and <i>B</i>=10.5 to 14 T, using conventional potentiometer and galvanometer systems. These values of <i>R</i>_H(4) are in agreement with those obtained by means of a preliminary system of Josephson potentiometer and SQUID galvanometer to within a few parts in 10⁷.