De Haas-van Alphen measurements of the Fermi surfaces of rubidium and cesium

Abstract

We present the results of a detailed investigation of the geometry of the Fermi surfaces of rubidium and cesium by means of the de Haas-van Alphen (dHvA) effect. By using samples of random orientation, mounted with the least constraints possible, we have obtained extensive coverage of the entire Fermi surface. An in situ NMR sample enabled the infinite-field phase of the signal, as well as absolute areas, to be determined. The spin-splitting factor cos (πgm*/2m 0 ), was found to be positive for both metals. The data, taken in magnetic fields up to 52 kG and at temperatures down to 1.1 K, was fitted by a 10- and 12-term cubic harmonic model expansion for rubidium and cesium, respectively. These models indicate that the Fermi surfaces are somewhat more distorted than those derived from previous investigations. A large change in the signal amplitude of cesium with crystal orientation suggests a variation in the productgms* over the Fermi surface. Effective mass measurements in cesium show a significant discrepancy between the measured dHvA and specific heat masses.