February 16, 2016

Laser-activated superconductor

Shining lasers at superconductors can make them work at higher temperatures, suggests new findings from an international team of scientists including the University of Bath.

Superconductors are materials that conduct electricity without power loss and produce strong magnetic fields. They are used in medical scanners, super-fast electronic circuits and in Maglev trains which use superconducting magnets to make the train hover above the tracks, eliminating friction.

The team, led by the Max Planck Institute for the Structure and Dynamics of Matter and including the Universities of Bath and Oxford, shone a laser at a material made up from potassium atoms and carbon atoms arranged in bucky ball structures and found it to still be superconducting at more than 100 degrees Kelvin – around minus 170 degrees Celsius.

The researchers hope these findings could lead to new routes and insights into making better superconductors that work at higher temperatures.


Structure and equilibrium optical properties of K3C60.

Nature - Possible light-induced superconductivity in K3C60 at high temperature



Superconducting at higher temperatures

Dr Stephen Clark, theoretical physicist at the University of Bath, worked with his experimental physicist colleagues to try to understand how superconductivity might emerge when the material is exposed to laser radiation.

He explained: “Superconductors currently only work at very low temperatures, requiring expensive cryogenics – if we can design materials that superconduct at higher temperatures, or even room temperature, it would eliminate the need for cooling, which would make them less expensive and more practical to use in a variety of applications.

“Our research has shown we can use lasers to make a material into a superconductor at much higher temperatures than it would do naturally. But having taken this first step, my colleagues and I will be trying to find other superconductors that can be coerced to work at even higher temperatures, possibly even at room temperature.

“Whilst this is a small piece of a very large puzzle, our findings provide a new pathway for engineering and controlling superconductivity that might help stimulate future breakthroughs.”

The non-equilibrium control of emergent phenomena in solids is an important research frontier, encompassing effects such as the optical enhancement of superconductivity. Nonlinear excitation of certain phonons in bilayer copper oxides was recently shown to induce superconducting-like optical properties at temperatures far greater than the superconducting transition temperature, Tc. This effect was accompanied by the disruption of competing charge-density-wave correlations which explained some but not all of the experimental results. Here we report a similar phenomenon in a very different compound, K3C60. By exciting metallic K3C60 with mid-infrared optical pulses, we induce a large increase in carrier mobility, accompanied by the opening of a gap in the optical conductivity. These same signatures are observed at equilibrium when cooling metallic K3C60 below Tc (20 kelvin). Although optical techniques alone cannot unequivocally identify non-equilibrium high-temperature superconductivity, we propose this as a possible explanation of our results.

SOURCES- University of Bath, Nature

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