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Sound propagation experiments in a magnetic field in superfluid /sup 3/He-B

Thesis/Dissertation ·
OSTI ID:5940140

A high resolution, acoustic impedance technique was used to investigate the order parameter collective modes in superfluid /sup 3/He-B. Theoretically, a classification of the collective modes in the B-phase based on a total angular momentum quantum number, J, is appropriate. In agreement with earlier experiments, the J = 2 real mode or the real squashing mode was observed to split into five components in small magnetic fields. However, contrary to earlier theoretical estimates, the Zeeman shifts were found to become extremely nonlinear as the magnetic field is increased. The extent of nonlinearity is larger at low pressures and at temperatures close to T/sub c/. The nonlinear Zeeman shifts are explained as the result of the distortion of the B-phase energy gap. In addition to gap distortion the coupling between the same J/sub z/ substates of the different J modes are also found to contribute to the nonlinearity and in this sense the nonlinear evolution of the real squashing mode constitutes the observation of the Paschen-Back effect in /sup 3/He-B. A comparison of the observed Zeeman shifts with the theoretical expressions has yielded a wealth of information about particle-particle and particle-hole interaction effects in superfluid /sup 3/He.

Research Organization:
Northwestern Univ., Evanston, IL (USA)
OSTI ID:
5940140
Country of Publication:
United States
Language:
English