This Physics department Condensed Matter Physics Talk is scheduled for Thursday, April 2, from 3:30-4:30 pm in Room 137. Refreshments are served from 3:15-3:30 pm in the same room.

Acoustic Studies of Two-Dimensional Structures with High Conductivity
Dr. Alexey V. Suslov, National High Magnetic Field Lab, Florida State University

I will give a review of DC field facility at the National High Magnetic Field Laboratory and present a novel detector, which I recently designed and built for ultrasonic experiments in High magnetic fields. I will describe our results obtained by the surface acoustic wave technique on two–‐dimensional (2D) structures with quantum Hall effect. We use this technique for studies of complex ac conductivity of 2D carriers.

Measurements on a p–‐GeSi/Ge/GeSi (p=6×10**11 cm–‐2) single quantum well were performed in tilted magnetic fields and revealed that the in-plane component of the magnetic field affects the g-factor and the cyclotron effective mass of the holes.

Our studies of single 65nm quantum well AlGaAs/GaAs/AlGaAs structure (n=5×10**10 cm–‐2 and μ=8.5×10**6 cm2/Vs) were focused in the vicinity of the filling factor 1/5. In this region, observed frequency dependence of the ac conductivity is of a resonance nature. Such a behavior of ac conductivity could be interpreted as manifestation of a pinning mode of a Wigner crystal.