Test of the charge density wave model of potassium

Abstract

Predictions of the charge density wave (CDW) model for potassium are tested by high-field induced torque experiments. The CDW model is described to show the open orbits on the Fermi surface of potassium with a CDW. Expressions for the induced torque are developed in terms of the resistivity and other parameters of the sample. The induced torque as a function of magnetic field direction shows sharp structure above 3–4 T with more than 20 peaks in 180° rotation. The peaks have the character of open orbits and the large number is predicted by the CDW model. The magnetic field, sample orientation, and temperature dependences of induced torque are also investigated. The magnetic field dependence agrees with that expected from open orbits with magnetic breakdown. However, the open orbits that would cause the induced torque peaks are not in directions predicted by the CDW model. Variation of induced torque with temperatures between 1.4 and 2.1 K can be explained by some of the features of the model although the observed changes are larger than those predicted. The conclusion is that the CDW model explains many of the properties of the high-field induced torque structure.