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|Title:||Influence of Pressure on the Cyclotron Mass of Potassium and Hole Fermi Surface of Antimony|
|Authors:||El-Rahman, Abd Afaf|
|Abstract:||<p>Detailed investigations of the hydrostatic pressure dependences of the hole Fermi surface of antimony and the cyclotron effective masses of antimony and potassium were made in the pressure range from 1 bar to 4.4 kbar, by means of the de Haas-van Alphen (dHvA) effect. Solid helium was used as a pressure transmitting medium. These measurements were made using the field modulation measuring technique, modified to optimize the sensitivity and selectivity of the dHvA spectrometer action. The effect of pressure on the anisotropy of the entire hole Fermi surface in the trigonal-bisectrix crystallographic plane was determined in detail. The pressure derivatives of the extremal cross-sectional areas of the surface were found to differ in sign and magnitude for various field directions. The total departure of the hole Fermi surface from a perfect ellipsoid in this crystallographic plane was accurately calculated at standard atmospheric pressure (1 bar) and at a pressure of 1.08 kbar, using the ellipsoidal-parabolic approximation. It was found that the anisotropy and shape of the surface are greatly influenced by pressure. The tilt angle was found to be insensitive to pressure within quoted experimental error.</p> <p>The cyclotron effective masses were derived from the temperature dependence of the dHvA amplitude. In potassium, the logarithmic pressure derivative, (1/m*)dm*/dP, was found to be -(0.71±0.12)x10⁻² kbar⁻¹, and the standard atmospheric pressure cyclotron effective mass was determined to be (1.211±0.005) m₀, where m₀ is the free electron mass. The observed decrease of the quasiparticle mass with increasing pressure was analyzed and explained in terms of changes of the band structure effects and many-body effects with pressure. In antimony, the cyclotron effective mass associated with the minimum section of the hole Fermi surface was determined to be (0.0637±0.0005) m₀ at standard atmospheric pressure, in agreement with the calculated band structure mass of Pospelov and Grachev of 0.06 m₀. The cyclotron mass was found to be nearly insensitive to pressure with (l/m*)dm*/dP = + (0.16=0.39)xl0⁻² kbar⁻¹. The study of the pressure dependence of m* in these elements along with a theory proposed by Trofimenkoff and Carbotte for the pressure dependence of the electron-phonon mass enhancement parameter, λep, permits the magnitudes of the changes of the band structure mass and λep with pressure to be deduced in these elements.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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