Broadband Frequency Study of the Zero Sound Attenuation near the Quantum Limit in Normal Liquid ³He close to the Superfluid Transition

The zero sound attenuation, α₀(ω, T, P), of normal liquid ³He has been studied over a broad range of frequency (ω/2π = 8 - 50 MHz). Data has been collected at a constant temperature (T ≈ 1.1 mK) which is just above the superfluid transition temperature, T_c, when the liquid is near a pressure, P, of 1 bar. The results are compared to Landau's prediction in the quantum limit, k_BT « (Latin small letter h with stroke)ω « k_BT_F, where α₀(ω, T, P) = α′(P) T²[1 + ((Latin small letter h with stroke)ω/2πk_BT)²]. Deviations from Landau's prediction are compared to the results of other workers and are discussed with respect to additional (unidentified) extrinsic background effects and (possible) intrinsic scattering mechanisms due to fluctuations in the liquid.