Transverse acoustic impedance measurements for surface states of superfluid ³He A ₁ and A ₂ phases

We measured the complex transverse acoustic impedance in both superfluid ³He A ₁ and A ₂ phases. This impedance is sensitive to surface states. In our preliminary results, the temperature dependence of the impedance in the A ₁ phase is similar to that in A phase, and the imaginary part shows an anomaly in the A ₂ phase. These anomalies occurred at the temperature defined as T _k, which is lower as the frequency gets higher. The similar frequency dependence of T _k in each phase suggests that the anomaly is attributed to the same origin. The frequency dependence of the T _k /T _c indicates that the shape of the surface density of each spin pair state did not greatly change in the present experimental temperature range.