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Unconventional phenomena are triggered by acoustic waves in 2-D materials

Unconventional phenomena are triggered by acoustic waves in 2D materials

Two interdigital transducers (IDT's) generate and detect acoustic waves for surface (SAW's, orange arrow). Between the IDTs, these waves interact with the 2D electrodes such as molybdenum disulfide (MoS2), and give rise to conventional and unconventional acousto-electric currents. MoS2 is separated from the piezoelectric substrate by a dielectric layer. Credit: IBS

Researchers at the Center for Theoretical Physics of Complex Systems (PCS), within the Institute for Basic Science (IBS, South Korea), and colleagues have reported on a new phenomenon, called Acoustoelectric Effect, occurring in 2- D materials, similar to graphing. This study will be published in Physical review letters and brings new insights into the study of valleytronics.

In acoustic electronics, surface acoustic waves (SAWs) are used to generate electrical currents. In this study, the team of theoretical physicists modeled the propagation of SAWs in emerging 2-D materials, such as monohydric molybdenum disulfide (MoS).2). SAWs drag MoS2 electrodes (and gaps), making an electric current with conventional and unconventional components. The latter consists of two contributions: a warping-based stream and a Hall stream. The first is directional-dependent, is related to "so-called" counts – electrons & # 39; local energy minima – and resembles one of the mechanisms that explain photovoltaic effects of 2-D materials exposed to light. The second is due to a specific effect (Berry phase) that has an influence on the velocity of these electrodes traveling as a group and resulting in intriguing phenomena such as anomalous and quantum Hall effects.

The team analyzed the characteristics of an acoustic-electric current, suggesting a way to independently run and measure conventional, warping and Hall currents. This allows you to simultaneously utilize both optical and acoustic techniques to control the propagation of carriers in new 2-D materials, creating new logical devices.

Unconventional phenomena are triggered by acoustic waves in 2D materials

Store patterns from & # 39; e the x and y components of & # 39; e conventional (a, d), warping (b, e) and hall (c, f) electric current density. Yellow damage marks the areas of negative current (directed opposite the x-axis y-axis). Red dots manifest the special angles, where only the unconventional stream flows along the x or y direction. Credit: IBS

The researchers are interested in checking the physical properties of these ultra-thin systems, especially those that are free to move in two dimensions, but tightly in & # 39; containing a third. By limiting the parameters of & nbsp; electrodes, in & # 39; Especially their momentum, spider, and drop, it will be possible to research technologies outside silicon electronics. For example, MoS2 has two district valleys, which can be potentially used in a future for bit storage and processing, making it an ideal material to immerse in valleytronics.

"Our theory opens a way to manipulate valley transport through acoustic methods, and to extend the application of dental effects to acousto-electronic devices," explains Ivan Savenko, leader of Light-Matter Interaction in Nanostructures Team at PCS.

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More information:
A. V. Kalameitsev et al., Valley Acoustoelectric Effect, Physical review letters (2019). DOI: 10.1103 / PhysRevLett.122.256801

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Unconventional phenomena triggered by acoustic waves in 2-D materials (2019, July 23)
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