2023-08-05 20:10:00
The behavior of the electron in quantum insulators, a subject of long-standing debate and research, has been surprisingly revealed by a team of researchers from theCornell University. Instead of traveling around the edges of the material, as previously believed, they discovered that the transport current travels through the interior of the material.
These results could have major implications for the development of topological materials for future quantum devices.
The strange behavior of the electron
The study, published in Nature Materials, was led by the team of assistant professor of physics Katja Nowack, with Matt Ferguson, Ph.D. ’22, as lead author. The objective was to better understand the so-called anomalous quantum Hall insulators. These intriguing materials show unique quantum behaviors when subjected to magnetic fields.
The project was born from the observation of the quantum Hall effect. This effect was discovered in 1980 and occurs when a magnetic field is applied to a specific material, causing an unusual manifestation: the inside of the sample becomes an insulator, while an electric current moves in one direction along the outer edge. Resistors are quantized, or restricted, to a value defined by a fundamental universal constant.
The controversial concept of the anomalous quantum Hall insulator
An anomalous quantum Hall insulator, which was first discovered in 2013, achieves the same effect using a material that is magnetized. The electrons move along the edge without dissipating energy, a behavior reminiscent of a superconductor. However, this popular perception is changing.
“The idea that current flows along edges may very well explain how you get this quantization. But it turns out it’s not the only image that can explain the quantization,” Nowack said. “Edge imagery has really been dominant since the dramatic rise of topological insulators in the early 2000s.”
Direct observation of electron transport
For this new study, Nowack’s team focused on chromium-doped bismuth antimony telluride, the same compound in which the anomalous quantum Hall effect was first observed a decade ago. They used a superconducting quantum interference device, or SQUID, an extremely sensitive magnetic field sensor that can operate at low temperatures to detect infinitely small magnetic fields. The SQUID effectively images flux currents, which are what generate the magnetic field.
Reconsider the understanding of topological materials
When the researchers observed electrons flowing through the bulk of the material, not around the edges, they began to revisit old studies. They found that there had been much debate about the exact location of the flux after the original discovery of the quantum Hall effect in 1980.
“I hope the new generation working on topological materials will take note of this work and reopen the debate. It’s clear that we don’t even understand some very fundamental aspects of what’s going on in topological materials,” Nowack said.
Synthetic
In sum, this study challenges the traditional understanding of current flow in anomalous quantum Hall insulators. She emphasizes the importance of understanding both the general principles and the finer nuances that dictate the behavior of topological materials. This understanding could be crucial for the development of more complex hybrid technologies.
For a better understanding
What is an anomalous quantum hall insulator?
It is a material that exhibits unique quantum behaviors when subjected to magnetic fields, allowing electrons to move without energy dissipation.
What does Nowack’s team’s discovery mean for understanding topological materials?
It challenges the traditional perception that current only flows along the edges of the material. Instead, they discovered that the current flows through the interior of the material.
What are the implications of this discovery?
This could have major implications for the development of topological materials for future quantum technologies.
The team’s paper, titled “Direct Visualization of Electronic Transport in a Quantum Anomalous Hall Insulator,” was published August 3 in Nature Materials. The lead author is Matt Ferguson, Ph.D. ’22, currently a postdoctoral researcher at the Max Planck Institute for Chemical Solid State Physics in Germany. DOI: 10.1038/s41563-023-01622-0
Co-authors are PhD student David Low and Pennsylvania State researchers Nitin Samarth, Run Xiao, and Anthony Richardella.
The research was primarily supported by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, US Department of Energy.
Materials growth and sample fabrication were supported by the National Science Foundation-funded 2D Crystal Consortium – Materials Innovation Platform (2DCC-MIP) at Penn State.
[ Rédaction ]
1691292622
#Current #takes #surprising #route #quantum #material