Physicists Discover New Phenomena in Fractional Quantum Hall Effects

Imagine a flat, two-dimensional world, instead of our three-dimensional one, where the rules of physics are reversed and particles like electrons defy expectations to reveal new secrets. That’s exactly what a team of researchers, including Georgia State University physics professor Ramesh G. Mani and recent U.S. Ph.D. graduate Kushan Wijewardena, have been studying in the university’s labs.

Their studies led to a discovery recently published in the journal Physics of communicationsThe team investigated the enigmatic world of fractional quantum Hall effects (FQHE), discovering new and unexpected phenomena when these systems are probed in new ways and pushed beyond their usual limits.

“Research into fractional quantum Hall effects has been a major focus of modern condensed matter physics for decades, because particles on the flat surface can have multiple personalities and can exhibit context-dependent personality on demand,” Mani said. “Our latest findings push the boundaries of this field, providing new insights into these complex systems.”

The quantum Hall effect has been a vibrant and vital area of ​​condensed matter physics since 1980, when Klaus von Klitzing announced his discovery that a simple electrical measurement could yield very precise values ​​for some fundamental constants that determine the behavior of our universe. This discovery earned him a Nobel Prize in 1985.

In 1998, a Nobel Prize was awarded for the discovery and understanding of the fractional quantum Hall effect, which suggested that flat particles could have fractional charges. The journey continued with the discovery of graphene, a material that showed the possibility of massless electrons in flat particles, leading to another Nobel Prize in 2010.

Finally, theories on new phases of matter, linked to the quantum Hall effect, were rewarded with a Nobel Prize in 2016.

Condensed matter physics has led to discoveries that have made possible modern electronics such as cell phones, computers, GPS, LED lighting, solar cells, and even self-driving cars. The science of flat terrain and flat terrain materials are now being studied in condensed matter physics with the goal of making more energy-efficient, flexible, faster, and lighter electronic devices of the future, including new sensors, more efficient solar cells, quantum computers, and topological quantum computers.

In a series of experiments in extremely cold conditions, near -273 °C (-459 °F) and under a magnetic field nearly 100,000 times stronger than Earth’s, Mani, Wijewardena and their colleagues set to work. They applied extra current to high-mobility semiconductor devices made from a sandwich structure of gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) materials, which allows electrons to be realized in a flat field.

They observed that all FQHE states split unexpectedly, followed by split branch crossings, which allowed them to explore the novel non-equilibrium states of these quantum systems and reveal entirely new states of matter.

The study highlights the crucial role of high-quality crystals, produced at the Swiss Federal Institute of Technology Zurich by Professor Werner Wegscheider and Dr Christian Reichl, in the success of this research.

“The traditional study of fractional quantum Hall effects can be compared to exploring the ground floor of a building,” Mani explains. “Our study is about searching for and discovering the upper floors – those exciting, unexplored levels – and finding out what they look like. Amazingly, with a simple technique, we were able to access these upper floors and discover complex signatures of excited states.”

Wijewardena, who earned his doctorate in physics from Georgia State University last year and is now on the faculty at Georgia College and State University in Milledgeville, expressed enthusiasm for their work.

“We have been working on these phenomena for many years, but this is the first time we report these experimental results on obtaining excited states of fractional quantum Hall states induced by applying a DC bias,” Wijewardena said. “The results are fascinating, and it took us some time to have a feasible explanation for our observations.”

The study not only challenges existing theories but also suggests a hybrid origin for the observed FQHEs in nonequilibrium excited states. This innovative approach and the unexpected results highlight the potential for new discoveries in the field of condensed matter physics, inspiring future research and technological advances.

The team’s findings extend well beyond the lab and point to potential prospects for quantum computing and materials science. By exploring these uncharted territories, these researchers are laying the groundwork—and training new generations of students—for future technologies that could revolutionize everything from data processing to energy efficiency, while also powering the high-tech economy.

Mani, Wijewardena, and their team are now expanding their studies to even more extreme conditions, exploring new methods to measure the complex parameters of the plains. As they progress, they expect to uncover new nuances in these quantum systems, bringing valuable insights to the field. With each experiment, the team moves closer to understanding the complex behaviors at play, while remaining open to the possibility of new discoveries along the way.