3 research outputs found
Model of the low temperature magnetic phases of gadolinium gallium garnet
The magnetic behaviour of gadolinium gallium garnet in an external magnetic ļ¬eld at zero temperature is considered. For high ļ¬elds a classical spin model of the gadolinium ions predicts a spin conļ¬guration that is periodic at the level of the smallest repeating unit cell. The quantum version of the model is treated via a truncated Holstein-Primakoļ¬ transformation with axes deļ¬ned by the classical spin conļ¬guration, and the magnon excitation bands are calculated. The model predicts a transition in the ļ¬eld range of 1.9-2.1 T, sensitive to the direction of the applied ļ¬eld, which is caused by one or more magnon modes becoming soft as the ļ¬eld is decreased. In general the soft modes occur at incommensurate wavevectors and therefore break the periodicity of the spin conļ¬guration below the transition. One exception occurs when the ļ¬eld aligns with one of the principle crystal axes, in which case periodicity of the spin conļ¬guration is found to be maintained on a larger crystallographic cubic cell even below the transition. This simple case is studied in more detail. Comparisons are drawn with existing experimental data, and further experimental tests of the model are suggested. [Abstract copyright: Ā© 2021 IOP Publishing Ltd.
Pulsed Magnetic Field Measurements of the Composite Fermion Effective Mass
Magnetotransport measurements of Composite Fermions (CF) are reported in 50 T
pulsed magnetic fields. The CF effective mass is found to increase
approximately linearly with the effective field , in agreement with our
earlier work at lower fields. For a of 14 T it reaches , over 20
times the band edge electron mass. Data from all fractions are unified by the
single parameter for all the samples studied over a wide range of
electron densities. The energy gap is found to increase like at
high fields.Comment: Has final table, will LaTeX without error
Spin-Charge Separation, Anomalous Scaling and the Coherence of Hopping in exactly solved Two Chain Models
The coherence of transport between two one-dimensional interacting Fermi
liquids, coupled by single particle hopping and interchain interaction, is
examined in the context of two exactly soluble models. It is found that the
coherence of the inter-chain hopping depends on the interplay between
inter-chain hopping and inter-chain interaction terms, and not simply on the
ground state spectral properties of an isolated chain. Specifically, the
splitting of levels in associated with interchain hopping in a soluble
model is found to be enhanced by the introduction of interchain interaction. It
is also shown that, for an exactly solvable model with both and
interactions, coherent interchain hopping coexists with anomalous scaling and
non-Fermi liquid behavior in the chain direction.Comment: Two postscript figure