Researchers engineer electrically tunable graphene devices to study rare physics

The National Graphene Institute (NGI) in the UK and the Penn State College of Engineering in the US collaborated to develop a platform that allows for fine control over the interaction between light and Graphene. The results were published in Science.

According to the researchers, the work could advance optoelectronic technologies to better generate, control and sense light and potentially communications. They demonstrated a way to control the THz waves. The feat could contribute to the development of wireless technology for high-speed communication networks.

Strong and weak interactions.

Light and matter can be weakly correlated but not change each other's constituents, or strongly correlated but not change the system, where their interactions can fundamentally change the system. Researchers have solved the challenge of controlling the shift from weak to strong and back.

Coskun Kocabas, professor of 2D device materials at The University, said that they have demonstrated a new class of optoelectronic devices using concepts of topology.

The Henry Royce Institute for Advanced Materials is located in Manchester.

There are special points in an open system. They are sensitive and respond to even the smallest changes to the system.

At an exceptional point, the energy landscape of the system is considerably modified, resulting in reduced dimensionality and skewed topology. Control of exceptional points, and the physical processes that occur at them, could lead to applications for better sensors.

There is a platform composition.

A gold-foil gate electrode forms a bottom reflective mirror in the platform the researchers developed. A top mirror is formed by a book-ended layer of Graphene. Control of the top mirror's reflectivity can be achieved by changing the applied voltage. The middle of the device is where the alpha lactose is located.

The system is controlled by two people. One can change the length of the cavity by raising the lower mirror to adjust the frequencies of resonation and the number of oscillators for the system. The top graphene mirror has a voltage applied to it that affects its reflective properties. The tuning shifts weakly coupled terahertz light and organic molecule to become strongly coupled.

There are exceptional points between the weak and strong light regimes.

He noted that these points are typically studied and observed in the relationship between analogous modes or systems.

Kocabas said that this work is one of the rare cases where exceptional points are demonstrated.

The THz spectrum has an unprecedented phase modulation.

The system is driven to an exceptional point and beyond by the researchers. The geometric properties of the system change before and after the exceptional point.

The phase modulation describes how a wave changes when it interacts with the THz field. The researchers said that controlling the phase and amplitude of THz waves is a technological challenge. The researchers measured how the system responded to the changes they made. Depending on the system's topology at the point of measurement, phase modulation could range from zero to four magnitudes larger.

The device can be steered through an exceptional point, which allows electrical control of the reflection topology.

According to the researchers, the control of light-matter interactions around an exceptional point enabled by the graphene-based platform has potential applications ranging from topological optoelectronic and quantum devices to topological control of physical and chemical processes.

More information: Topological engineering of terahertz light using electrically tuneable exceptional point singularities, Science (2022). DOI: 10.1126/abn6528 Journal information: Science Citation: Researchers engineer electrically tunable graphene devices to study rare physics (2022, April 7) retrieved 7 April 2022 from https://phys.org/news/2022-04-electrically-tunable-graphene-devices-rare.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.