Physicists prove a 30-year-old theory — the even-denominator fractional quantum Hall state — and establish bilayer graphene as a promising platform that could lead to quantum computation.
Two independent research teams observed same behavior in double bilayer graphene.
This week at the lab, a MagLab physicist is developing a measurement technique that will help scientists identify and understand new states of matter in a new class of metals analogous to graphene.
The MagLab offers dozens of measurement techniques to scientists — everything from AC magnetic susceptibility to ultrafast magneto-optics. Brad Ramshaw of the MagLab's Pulsed Field Facility at Los Alamos National Laboratory (LANL) in New Mexico, is modernizing a technique called pulsed echo ultrasound.
If you yell across a valley to a canyon on the other side, you can figure out how far it is by measuring the time between your holler and the echo it generates. "That's what pulsed echo ultrasound is, except we're not doing it in the canyon," explained Ramshaw, whose project is funded by a two-year, $430,000 grant from LANL. "We're taking a little piece of material and we're yelling at it."
The twist is that instead of measuring distance (they already know the length of the material), they are measuring the speed at which the sound travels, which differs depending on the material, magnetic field and temperature. This data can shed light on the physics happening inside the material.
Of course, it's a little more complex than shouting across a canyon, Ramshaw explained. "We have an ultrasonic transducer — like the ones used for ultrasound imaging in a hospital, but much smaller — that sends a pulse of sound at the material. Then the sound travels across it, bounces off the end and comes back to the transducer."
It's no coincidence that Ramshaw is developing the technique at the Pulsed Field Facility, which houses instruments that create brief pulses of magnetic fields (measured in milliseconds) as strong as 100 tesla, the strongest such magnets in the world.
Fields that high, used in concert with this technique, are expected to reveal new physics about Weyl metals, which can be thought of as three-dimensional analogs of graphene. A one-atom thick compound with exciting properties — incredible strength, flexibility and electrical and heat conductivity — graphene holds great promise for communications, transportation and other industries. The hope is that Weyl metals will hold similar promise for electronics applications, but will be easier to manipulate and manufacture.
Scientists have been aggressively studying graphene since they learned how to make it in 2004. The technique Ramshaw is developing will open a new playground for physicists to explore its 3-D analog, including the unusual way its electrons behave, as if they had no mass.
The Pulsed Field Facility's world-record fields are, " … enough to do crazy electronic things to these materials," said Ramshaw. "This is a capability that users want and we now have the resources to develop it."
Text by Kristen Coyne
New kind of quantum Hall state observed in graphene superlattices.
A material that you may never have heard of could be paving the way for a new electronic revolution.
FSU researchers use MagLab's unique 9.4 tesla ICR machine to make discovery.
MagLab scientists working with graphene — a stronger-than steel, but feathery light material with a myriad of intriguing attributes — have observed new properties that bring this high-tech super material closer to everyday use.
Researchers from Columbia University working at the MagLab have observed a physical phenomenon in bilayer graphene that could usher in a new generation of quantum computers.
Using the high magnetic fields available at the NHMFL, users from MIT were able to observe a quantum spin hall (QSH) state in graphene. The QSH state results in two oppositely oriented spin currents flowing clockwise and counter clockwise around the edge of the graphene flake without dissipation effects. This discovery further advances the exciting work being done to bring about spin based electronics.
Utilizing the sensitivity of the NHMFL optics facility, a team of scientists from Georgia Tech, Sandia National Laboratories, Institut Néel, Université Paris-Sud and the NHMFL were able to observe collective oscillations of Dirac Fermions in graphene nanoribbons. The observed effect is tunable by varying the width of the graphene nanoribbons and the applied magnetic field. This observation raises the possibility of graphene based tunable THz devices.