We have observed both geometric and open-orbit resonances in the ultrasonic attenuation in thallium at frequencies up to 460 Mc/sec. Sound was propagated in the , [11̄20], and [10̄10] directions and extremal k vectors in the planes perpendicular to these propagation directions were measured. The measured k vectors agree well with the calculated values of Soven for the major pieces of the Fermi surface. We also observed an open-orbit resonance and several subharmonics for q^ parallel to  and H^ parallel to [11̄20]. This results from magnetic breakdown between zones 3 and 4 in the vicinity of the AL line. No open orbits along the c axis were observed, probably indicating that the fourth-zone electron surface does not contact the ALH plane.
ASJC Scopus subject areas
- Physics and Astronomy(all)