Zero sound in anisotropic metals

✍ Scribed by Y.C Cheng; N.D Mermin

• Publisher: Elsevier Science
• Year: 1970
• Tongue: English
• Weight: 958 KB
• Volume: 60
• Category: Article
• ISSN: 0003-4916
• DOI: 10.1016/0003-4916(70)90480-x

✦ Synopsis

The Gor'kov-Dzyaloshinskii theory of zero sound in anisotropic metals is generalized, and applied to specific metals. The main generalizations are: (a) sufficient conditions for the existence of zero sound are derived without the assumption of weak coupling: (b) examples are discussed in which these conditions are satisfied even when the propagation vector does not lie along or close to a symmetry axis. A survey of metallic Fermi surfaces indicates that zero sound may be possible in the noble metals along directions close to the [ill] direction, and in beryllium and graphite along directions close to the c axis. It may also be possible in the semimetal bismuth (and perhaps antimony and arsenic) along certain nonsymmetry directions. In all these cases sufficient conditions on the Landau F-function are derived for zero sound modes to exist at infrared frequencies (and, in some cases, at radio frequencies.) The conditions can be satisfied in the weak coupling limit, provided Fhas the appropriate sign. Unfortunately this is beyond reliable theoretical calculation, and the final question of whether the modes exist is best settled by experiment.