Abstract
We present the results of an investigation of the de Haas-van Alphen (dHvA) effect in the heavy fermion superconductor UPt3.Oscillations composed of up to 8 frequency components, corresponding to cyclotron orbits in a plane normal to the a-axis, have been detected in a high purity single crystal and a study of their amplitude as a function of temperature and magnetic field has been performed in the intervals 20–150 mK and 40–115 kG, respectively. From this study we obtain estimates of the cyclotron masses, found to range approximately from 25 to 90 times the bare electron mass, and of the mean free path, found to be in excess of 1000 Å. The relationship between these findings and the results of conventional energy band calculations is discussed.
Highlights
Whereaand th arequantitieswhicharenormallyindependent of TandH, a n d hko, m* a n d lo are, respectively, the momentum, the effective mass, and the effective mean free path of quaslpartlcles near the Fermi level T h e velocity vo of the quaslpartlcles at the Fermi level is given by m*vo = hko F r o m eq (1) It IS seen that ko is determined from the frequency of the oscillations, m* from the temperature dependence of the amplitude at fixed H, a n d In f r o m the field dependence of the amplitude at fixed T
In the more general case of several partly filled anisotropic conduction bands an oscillatory magnetlsationM IS associated with eachextremal cross-sectional area M of the Fermi surface lying In a plane normal to H The fundamental component of M parallel to H for a given area M is in general still givenby eq (1), where ko, m* a n d lo are appropriate averages associated with the orbit around M k0 is the average Fermi wavevector defined by M = ~rk~, m* is the cyclotron mass defined by m*= hko/vo, where 1leo is the average of the inverse of the quaslpar
For each group of quasipartlcles associated with an extremal area M of the Fermi surface, the corresponding de Haas-van Alphen (dHvA) frequency F =
Summary
The dHvA effect consists of an oscillatory variation/~/of the magnetisatlon as a function of the Inverse of the applied magnetic field H In accordance with the traditional theory for a Fermi liquid (see eg refs [7,8]) the frequency and amplitude of M provide a direct measure of the principal properties of quasiparticles near the Fermilevel (1 ethosequaslparticleswhich are responsible for the low temperature behavlour) In the simplest case of a paramagnet with one partly filled lsotroplc conduction band, the fund amentalcomponent of ~7/ at atemperatureT may be expressed as. The exotic low temperature behavlour of the lntermetaihc compounds called "heavy fermion superconductors", has been attributed to the existence of fermion quaslpartlcles with effective masses of unprecedented magnitude, of order 100 times greater than the bare electron mass [1,2,3,4,5,6] Of fundamental interest is the precise nature of these quaslpartlcles and the origin of the effective interactions which lead to the formatlon of the enigmatic superconducting ground states
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