Researchers Demonstrate 3D Quantum Hall Effect for the First Time
August 16, 2019 | Singapore University of Technology and DesignEstimated reading time: 2 minutes
The quantum Hall effect (QHE), which was previously known for two-dimensional (2D) systems, was predicted to be possible for three-dimensional (3D) systems by Bertrand Halperin in 1987, but the theory was not proven until recently by researchers from the Singapore University of Technology and Design (SUTD) and their research collaborators from around the globe.
The Hall effect, a fundamental technique for material characterization, is formed when a magnetic field deflects the flow of electrons sideways and leads to a voltage drop across the transverse direction. In 1980, a surprising observation was made when measuring the Hall effect for a two-dimensional (2D) electron gas trapped in a semiconductor structure—the measured Hall resistivity showed a series of completely flat plateau, quantized to values with a remarkable accuracy of one part in 10 billion. This became known as the QHE.
QHE has since revolutionized our fundamental understanding of condensed matter physics, generating a vast field of physics research. Many new emerging topics, such as topological materials, can also be traced back to it.
Soon after its discovery, researchers pursued the possibility of generalizing QHE from 2D systems to three dimensions (3D). Bertrand Halperin predicted that such a generalized effect, called the 3D QHE, is indeed possible in a seminal paper published in 1987. From theoretical analysis, he gave signatures for 3D QHE and pointed out that enhanced interactions between the electrons under a magnetic field can be the key to drive a metal material into the 3D QHE state.
Thirty years have passed since Halperin's prediction and while there have been continuing efforts in trying to realize 3D QHE in experiment, clear evidence has been elusive due to the stringent conditions required for 3D QHE - the material needs to be very pure, have high mobility, and low carrier density.
SUTD's experimental collaborator, the Southern University of Science and Technology (SUSTech) in China, has been working on a unique material known as ZrTe5 since 2014. This material is able to satisfy the required conditions and exhibit the signatures of 3D QHE.
In the research paper published in Nature, the researchers show that when the material is cooled to very low temperature while under a moderate magnetic field, its longitudinal resistivity drops to zero, indicating that the material transforms from a metal to an insulator. This is due to the electronic interactions where the electrons redistribute themselves and form a periodic density wave along the magnetic field direction (as illustrated in the image) called the charge density wave.
"This change would usually freeze the electron motion and the material becomes insulating, disallowing the electron to flow through the interior of the material. However, using this unique material, the electrons can move through the surfaces, giving a Hall resistivity quantized by the wavelength of the charge density wave," explained co-author Professor Zhang Liyuan from SUSTech. This in turn proves the first demonstration of the long speculating 3D QHE, pushing the celebrated QHE from 2D to 3D.
"We can expect that the discovery of 3D QHE will lead to new breakthroughs in our knowledge of physics and provide a cornucopia of new physical effects. This new knowledge, in one way or another, will also provide us new opportunities for practical technological development," said co-author, Assistant Professor Yang Shengyuan from SUTD.
Suggested Items
Incap US Hosts Annual Food Drive
04/30/2024 | IncapIncap US recently concluded its annual food drive, a tradition aimed at supporting the Greater Washington County Food Bank. This year marked the fourth year of the initiative, and we couldn’t be prouder of the collective effort that was made to its success.
Scanfil Uses Employee Engagement Survey to Improve
04/30/2024 | ScanfilOnce a year Scanfil arranges Employee Engagement Survey (EES) in order to get valuable insight from its employees. In EES all employees are invited to share their opinion, bring ideas for improvements, and contribute to making Scanfil a better place to work.
epoxySet Introduces EO-20E – Versatile, Electrically Conductive Epoxy
04/29/2024 | epoxySetepoxySet produces EPOXIOHM EO-20E an industry established, reliable electrically conductive epoxy designed for solder replacement, chip bonding and other intricate electronic and optoelectronic assemblies. This creamy paste has a an easy to use 1:1 mix ratio with a 48 hour work time.
The Right Approach: I Hear the Train A Comin'
04/25/2024 | Steve Williams -- Column: The Right ApproachTraining is often an afterthought in many organizations, and the longer a company has been in business, the more this seems to apply. Over the past couple of decades, it has been amazing to observe that the biggest offenders of this are the companies that overuse the sound bite, “Our most important assets are our people.” When you dig into the process and peel back the onion, their commitment to training is not commensurate with that statement.
Big Win for Defense Production Act Budget Allocation in FY24 Budget
04/23/2024 | I-Connect007 Editorial TeamOne year ago, President Biden issued a determination that chips and packaging are critical for national security. Since that time, much work has been done to continue the conversation in Washington, elevating the importance of the entire chips value chain, and including printed circuit boards and substrates, without which chips cannot operate.