Acoustoelectric Study of Microwave-Induced Current Domains.

Area of Science:

• Condensed matter physics
• Mesoscopic physics

Background:

• Two-dimensional electron systems exhibit complex behavior under magnetic fields and microwave radiation.
• Microwave-induced zero-resistance states are a phenomenon observed in such systems, with their origins debated.
• Conventional transport measurements can be influenced by sample edges and contacts.

Purpose of the Study:

• To investigate the properties of two-dimensional electron systems in the regime of microwave-induced zero-resistance states.
• To utilize surface acoustic waves (SAW) as a localized probe to understand the bulk properties of these states.
• To determine the role of sample geometry and potential inhomogeneities in the formation of zero-resistance states.

Main Methods:

• Utilizing surface acoustic waves (SAW) to probe the bulk of a two-dimensional electron system.
• Applying a perpendicular magnetic field and monochromatic microwave radiation.
• Measuring changes in SAW propagation velocity.
• Employing theoretical modeling to interpret SAW response and domain structures.

Main Results:

• SAW propagation velocity shows clear signatures related to the zero-resistance states.
• The SAW method confirmed that contacts and sample edges are not the source of these states.
• The SAW response was found to depend on the angle between the SAW propagation vector and the orientation of spontaneously formed domains.
• Evidence for an inhomogeneous phase under nonequilibrium conditions was obtained.

Conclusions:

• Surface acoustic waves provide a powerful, localized probe for studying nonequilibrium phenomena in condensed matter systems.
• The results confirm the formation of an inhomogeneous phase in microwave-induced zero-resistance states.
• This study validates SAW as a technique to decouple bulk phenomena from edge or contact effects.