M. E. Msall | Searcharxiv

arXiv2022

Scanning X-ray diffraction microscopy of a 6 GHz surface acoustic wave

Surface acoustic waves at frequencies beyond a few GHz are promising components for quantum technology applications. Applying scanning X-ray diffraction microcopy we directly map the locally resolved components of the three-dimensional strain field generated by a standing surface acoustic wave on GaAs with wavelength $λ\simeq500\,$nm corresponding to frequencies near 6 GHz. We find that the lattice distortions perpendicular to the surface are phase-shifted compared to those in propagation direction. Model calculations based on Rayleigh waves confirm our measurements. Our results represent a break through in providing a full characterization of a radio frequency surface acoustic wave beyond plain imaging.

cond-mat.mes-hall↗

arXiv2015

Acoustic Measurements of the Stripe and the Bubble Quantum Hall Phases

We launch surface acoustic waves (SAW) along both the $<110>$ and the $<1\bar{1}0>$ directions of a Hall bar and measure the anisotropic conductivity in a high purity GaAs 2-D electron system in the Quantum Hall regime of the stripe and the bubble phases. In the anisotropic stripe phase, SAW propagating along the "easy" $<110>$ direction sense a compressible behavior (finite resistance) which is seen in standard transport measurement only if current flows along the "hard" $<1\bar{1}0>$ direction. In the isotropic bubble phase, the SAW data show compressible behavior in both directions, in marked contrast to the incompressible quantum Hall behavior seen in transport measurements. These results challenge models that assume that both the stripe and the bubble phase consist of incompressible domains and raise important questions about the role of domain boundaries in SAW propagation.

cond-mat.mes-hall↗