THEORY OF MAGNETOTRANSPORT ANOMALIES IN ALKALI METALS (POTASSIUM, INDUCED-TORQUE, HALL RESISTIVITY)

XIAODONG ZHU, Purdue University

Abstract

The galvanomagnetic properties of alkali metals, especially those of potassium, are studied taking into account the existence of an incommensurate change-density wave (CDW) structure. Occurrence of the CDW broken symmetry truncates the Fermi surface with a large number of energy gaps. Furthermore, any macroscopic crystal is likely divided into CDW (')Q-domains. An orientational (')Q-texture leads to a preferred direction in the crystal. For such an exotic system the effective magnetoresistivity tensor is anomalous and is derived for various magnetic fields. The residual (zero-field) resistance is also anisotropic. For fields 0.5 - 3T, Hall coefficients are found to be anisotropic, and a longitudinal-transverse mixing effect is discovered. The diagonal elements of the magnetoresistivity tensor are found to have a linear magnetoresistance. When the field is increased above 4T sharp open-orbit magnetoresistance spectrum develops. From the theoretical magnetoresistivity tensor, the induced-torque amplitude and phase patterns for potassium spheres are calculated. The theory quantitatively explains all of the induced-torque anomalies found experimentally in the last fourteen years. An interacting electron system, which is free of the CDW instabilities, is also studied by considering its spin response to a weak sinusoidal magnetic field. The many-body correction G(,-)((')q,(omega)) caused by exchange and correlation is introduced to describe the correct wave-vector- and frequency-dependent spin susceptibility. The exact behavior of G(,-)((')q,(omega)) in the large-q limit is shown to be related to the pair distribution function g((')r) at r = 0. G(,-)((')q,(omega)) (--->) 4g(0)-1 /3, as q (--->) (INFIN).At metallic densities this value is negative, opposite in sign to the limit at small wave vectors. Thus the spin susceptibility for large wave vectors is suppressed, rather than enhanced, by many-body effects.

Degree

Ph.D.

Subject Area

Condensation

COinS