System Bits: Jan. 3

Clues to high-temp superconductivity
Offering clues about the microscopic origins of high-temperature superconductivity, physicists at Rice University’s Center for Quantum Materials (RCQM) have created a new iron-based material.

The material is a formulation of iron, sodium, copper and arsenic created by Rice graduate student Yu Song in the laboratory of physicist Pengcheng Dai. The recipe involves mixing ingredients in a pure argon atmosphere, sealing them in niobium canisters and baking them at nearly 1,000 degrees Celsius to produce a layered alloy in which iron and copper separate into alternating stripes, which is critical for the material’s usefulness in explaining the origins of high-temperature superconductivity, explained RCQM Director Qimiao Si.

By forming this regular pattern, disorder has been physically removed from the system, which is crucially important for being able to say something meaningful about what’s going on electronically. Si is a theoretical physicist who has worked to explain the origins of high-temperature superconductivity and similar phenomena for nearly two decades.

The Rice Center for Quantum Material’s new alloy is the first iron-based superconductor that can be continuously tuned from the superconducting phase to the Mott insulating phase. (Source: Rice University)

High-temperature superconductors are terrible conductors at room temperature and only become superconductors when they are cooled to a critical temperature so Dai explained that the central problem of high-temperature superconductivity is to understand the precise relationship between these two fundamental states of matter and the phase transition between them. “The macroscopic change is evident, but the microscopic origins of the behavior are open to interpretation, largely because there are many variables in play, and the relationship between them is both synergistic and nonlinear.”

Measurements on the new material support a localized theory about high temperature superconductivity that argues that fundamentally new physics arise — due to electron-electron interactions — at the critical point at which the materials transition from one phase to the other. In particular, the researchers said, the new material is the first member of a class of iron-based superconductors called pnictides (pronounced NIK-tides) that can be tuned between two competing phases: the superconducting phase in which electrons flow with no resistance, and a “Mott insulating” phase in which electrons become locked in place and do not flow at all.

The crystalline structure of the new layered material includes alternating stripes of iron (blue) and copper (red). The striping is critical for the material’s usefulness in explaining the origins of high-temperature superconductivity. (Source: Rice University)

Samples were made and some tests were performed at RCQM. Additional tests were performed at Chalk River Laboratories’ Canadian Neutron Beam Center in Ontario, the National Institute for Standards and Technology’s Center for Neutron Research in Maryland, Brookhaven National Laboratory in New York, Oak Ridge National Laboratory’s High Flux Isotope Reactor in Tennessee and the Paul Scherrer Institute’s Advanced Resonant Spectroscopies beamline in Switzerland.

Analyzing vehicle platooning
As driverless cars merge into the transportation system in the coming years, MIT researchers reminded that some believe autonomous vehicles may save fuel by trailing each other in large platoons since vehicles experience less aerodynamic drag when they drive close together. Researchers have studied some driverless scenarios.

MIT engineers have studied a simple vehicle-platooning scenario and determined the best ways to deploy vehicles in order to save fuel and minimize delays. (Source: MIT)

The MIT engineers have studied a simple vehicle-platooning scenario, and determined the best ways to deploy vehicles in order to save fuel and minimize delays. Their analysis showed that relatively simple, straightforward schedules may be the optimal approach for saving fuel and minimizing delays for autonomous vehicle fleets, and that the findings may also apply to conventional long-distance trucking and even ride-sharing services because they are similar problems from a systems point of view.

Sertac Karaman, the Class of 1948 Career Development Associate Professor of Aeronautics and Astronautics at MIT said that people who study these systems only look at efficiency metrics like delay and throughput, but he and his team look at those same metrics, versus sustainability such as cost, energy, and environmental impact.

The researchers are also applying their simulations to autonomous ride-sharing services. Karaman envisions a system of driverless shuttles that transport passengers between stations, at rates and times that depend on the overall system’s energy capacity and schedule requirements. The team’s simulations could determine, for instance, the optimal number of passengers per shuttle in order to save fuel or prevent gridlock.
“We believe that ultimately this thinking will allow us to build new transportation systems in which the cost of transportation will be reduced substantially,” he added.

Teaching programming basics with music
As part of a $3 million grant from the National Science Foundation to make major strides in computer programming literacy for K-12 students, researchers at the Georgia Institute of Technology and Northwestern University have built a musical, interactive tabletop exhibit that teaches the basics of computer coding to K-12 students.

By moving coasters along a projection surface on TuneTable, students make a musical piece using elements of computer programming. They tap the surface to play a series of beats, beeps and samples.

The table will be installed at the Museum of Design Atlanta in early 2017 and Chicago’s Museum of Science and Industry in the summer.

The table includes basic computing programming elements that people would use when learning programming formally for the first time, such as iteration and go-to statements. TuneTable’s interactive surface uses computer vision to detect printed markers — officially they’re called fiducials —  on the coasters. Each coaster is assigned a sound or programming command, such as a splitter or repeater. People link them together to form a chain of electronic and hip hop sounds.  

Coasters can be moved along TuneTable’s projection surface to make music using elements of computer programming (Source: Georgia Tech)