Anomalous acoustoelectric effect in La0.67Ca0.33MnO3 films

Area of Science:

• Condensed Matter Physics
• Materials Science
• Acoustoelectronics

Background:

• The acoustoelectric (AE) effect describes interactions between sound waves and charge carriers in materials.
• Surface acoustic waves (SAW) are mechanical waves propagating along the surface of a solid.
• Understanding AE effects in complex material systems is crucial for electronic device applications.

Purpose of the Study:

• To investigate the acoustoelectric effect in a LiNbO3/La0.67Ca0.33MnO3 layered structure.
• To characterize the contributions of the longitudinal AE effect under SAW propagation.
• To elucidate the physical mechanisms behind observed anomalous AE phenomena.

Main Methods:

• Fabrication of a monolithic layered structure using a LiNbO3 substrate and a La0.67Ca0.33MnO3 film.
• Experimental study of the acoustoelectric effect induced by surface acoustic waves.
• Analysis of the longitudinal AE effect, including its dependence on SAW propagation direction and temperature.

Main Results:

• An anomalous contribution to the longitudinal AE effect was discovered, independent of SAW propagation direction.
• This anomalous effect coexists with the ordinary (wave vector-dependent) AE effect.
• The anomalous AE effect is dominant near the metal-insulator transition, while the ordinary effect is prevalent at other temperatures.

Conclusions:

• The anomalous acoustoelectric effect arises from strong modulation of the film's conductivity due to SAW-induced elastic deformations.
• This finding highlights the significant influence of mechanical strain on electronic properties in layered materials.
• The results offer insights into the interplay between acoustic and electronic phenomena near phase transitions.