Test of the Charge Density Wave Model of Potassium Using the Induced Torque Method

Abstract

<p>The conductivity tensor of potassium was studied using the induced torque technique in two magnetometers. The response of the two magnetometers was calculated and tested with standard materials. The phase of the induced torque was calculated.</p> <p>The induced torque in potassium showed different behaviour in magnetic fields, below 0.2 T, between 0.2 and 4 T and above 4 T. A two-fold torque anisotropy with peaks separated by 180º was observed at low fields and a four-fold pattern with peaks separated by 90º is dominant up to fields of 4 T. At high fields there are peaks in the induced torque rotation pattern which are characteristic of open orbits in a metal. The amplitude and magnetic field direction of some of the peaks changes non-monotonically with temperature over the temperature range 1.1 to 2.1 K. The high field peaks are independent of the presence of the four-fold torque which depends on sample preparation.</p> <p>The amplitude and phase of the induced torque were calculated for two models, an ellipsoidal sample with free electron conductivity and a sample with a charge density wave ground state. The four-fold induced torque was quantitatively explained by an ellipsoidal sample. Reasons why a model of an ellipsoidal sample is valid were presented.</p> <p>Qualitative agreement between the high field peaks and the charge density wave model which predicts open orbits was obtained. A quantitative explanation of the temperature dependence could not be obtained. Other possible explanations of the high field peaks were considered and found to be unsuitable.</p>