We have produced and characterized spin-squeezed states at a temperature of 26 °C in a nuclear magnetic resonance quadrupolar system. The experiment was carried out on 133Cs nuclei of spin I=7/2 in a sample of lyotropic liquid crystal. The source of spin squeezing was identified as the interaction between the quadrupole moment of the nuclei and the electric field gradients present within the molecules. We use the spin angular momentum representation to describe formally the nonlinear operators that produce the spin squeezing on a Hilbert space of dimension 2I+1=8. The quantitative and qualitative characterization of this spin-squeezing phenomenon is expressed by a squeezing parameter and squeezing angle developed for the two-mode Bose-Einstein condensate system, as well as by the Wigner quasiprobability distribution function. The generality of the present experimental scheme points to potential applications in solid-state physics.
The Josephson Junction model is applied to the experimental implementation of
classical bifurcation in a quadrupolar Nuclear Magnetic Resonance system. There
are two regimes, one linear and one nonlinear which are implemented by the
radio-frequency term and the quadrupolar term of the Hamiltonian of a spin
system respectively. Those terms provide an explanation of the symmetry
breaking due to bifurcation. Bifurcation depends on the coexistence of both
regimes at the same time in different proportions. The experiment is performed
on a lyotropic liquid crystal sample of an ordered ensemble of $^{133}$Cs
nuclei with spin $I=7/2$ at room temperature. Our experimental results confirm
that bifurcation happens independently of the spin value and of the physical
system. With this experimental spin scenario, we confirm that a quadrupolar
nuclei system could be described analogously to a symmetric two--mode
Bose--Einstein condensate.Comment: 5 pages, 3 figure
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