ULTRASONIC ATTENUATION BY CONDUCTION ELECTRONS IN POTASSIUM

Measurements of ultrasonic attenuation due to electron-lattice interaction were made on potassium wire samples with a pulse-echo or resonant-decay technique from 2.5 to 20°K at frequencies between 200 and 400 kc/sec (ql1 region). The magnitude of the attenuation was found to be on the average 1.6 times larger than predicted by the free-electron theories on the basis of the measured values of electrical conductivity. The imperfect knowledge of the background introduced a maximum 30% error. Various reasons for the observed discrepancy are discussed, but the results may be within the limits of the approximations involved in the theories. The temperature and frequency dependence of the attenuation were found to be in good agreement with the theoretical expectations. © 1968 The American Physical Society.