Studies of uranium ditelluride in high magnetic fields show superconductivity switching off at 35 T, but reoccurring at higher magnetic fields between 40 and 65 T.
Scientists revealed previously unobserved and unexpected FQH states in monolayer graphene that raise new questions regarding the interaction between electrons in these states.
This work provides important insight into one of the parent materials of iron-based superconductors.
Scientists used high magnetic fields and low temperatures to study crystals of URu2–xFexSi2. Using these conditions, they explored an intriguing state of matter called the "hidden order phase" that exhibits emergent behavior. Emergent behavior occurs when the whole is greater than the sum of its parts, meaning the whole has exciting properties that its parts do not possess; it is an important concept in philosophy, the brain and theories of life. This data provide strict constraints on theories of emergent behavior.
Recent measurements of superconducting tapes in the MagLab's 45-tesla hybrid magnet shows that the power function dependence of current on magnetic field remains valid up to 45T in liquid helium, while for magnetic field in the plane of the tape conductor, almost no magnetic field dependence is observed. Thus design of ultra-high-field magnets capable of reaching 50T and higher is feasible using the latest high-critical current density REBCO tape.
Discovery could help scientists better understand exotic behaviors of electrons.
This week at the lab, we retired a 1990 Toyota and are parking a 2016 Mercedes in its spot.
That's the metaphor offered by Bryon Dalton, head of operations for the lab's DC Field Facility, for a big upgrade of the lab's world-record 45 tesla hybrid magnet: a new set of 3,500-pound vacuum pumps.
Good-bye roll-down windows and Bush Sr.-era fuel economy. Hello turn-by-turn navigation, Bluetooth wireless data link and 10-way power driver seat.
The $260,000 German-made vacuum pumps will improve reliability and performance, generate systems diagnostics, and allow staff to run the pumps remotely. "You're going to have a better feel for what's going on and better control over it," said Dalton.
The pumps play a critical role in the operation of the hybrid, which pairs a resistive magnet with a superconducting magnet of niobium-tin and niobium titanium that requires temperatures near absolute zero. Helium liquefied on site has a temperature of 4.7 Kelvin, making Plutonian weather seem tropical by comparison. By dropping that liquid helium to below atmospheric pressure, the vacuum pumps, used with a special cooling apparatus called a Joules-Thompson refrigerator, gets it down to 1.6 Kelvin. This turns it into a zero-viscosity "superfluid" and maximizes the hybrid's efficiency.
Photo by Stephen Bilenky, text by Kristen Coyne.
This week at the lab, engineers are winding a coil for a new, hybrid magnet system that will match the field strength of our own world-record magnet.
Two teams from two magnet labs located on two continents have joined forces on this project.
The High Field Magnet Lab (HFML), located in Nijmegen, the Netherlands, is building a continuous-field magnet designed to generate a field of 45 tesla, which will tie the record now held by the MagLab’s 45 tesla hybrid magnet. The National MagLab is lending its expertise to the effort by building the superconducting portion of the magnet; the HFML is building the resistive portion.
In the end, five spools of cables containing a total of 2 km of superconducting wire will be joined and wound to form a 5-ton coil. The winding process alone requires several months. “Electrically you have to continue that path from one length of conductor to the next,” said MagLab engineer Iain Dixon, who is heading up the project. “There’s a lot of care and a lot of checks that go on to make sure that the bends are in the right place and the cuts are in the right place."
The inter-lab collaboration has meant a lot of back and forth for both teams. Andries den Ouden, head of superconducting magnet technology at Nijmegen, was in Tallahassee recently.
"During the project operation, there are no walls between the two labs," said den Ouden. "There's an open exchange of information … I think that's one of the key benefits."
Text by Kristen Coyne / Photo by Stephen Bilenky.
Nicolas Doiron-Leyraud of Canada's Université de Sherbrooke talks about his recent experiments on cuprate superconductors, why he chose physics over philosophy, and what makes the MagLab a great place to do science.
New kind of quantum Hall state observed in graphene superlattices.