Upper critical field of iron-based superconductor discovered

First, some background

Superconductors are materials that, under certain conditions, conduct electricity with zero resistance: Electrons zip through with perfect efficiency. This behavior is often interrupted by a high magnetic field (the point at which superconductivity ceases is called the upper critical field). An important goal in the search for new superconductors is their ability to operate even in the presence of high fields.

Recently scientists have been experimenting with superconductors containing iron, long thought to be incompatible with superconductivity.

What did scientists discover?

Scientists took a simple superconductor based on a binary compound of iron and selenium, combined it with tellurium (creating FeTe_0.9Se_0.1) then fabricated it into a very thin film of material. Earlier measurements of this material had suggested it could retain zero resistance to magnetic fields above 100 tesla. The present study showed that estimate to be overly optimistic: Superconductivity in the material stopped at about 45 tesla. Scientists believe that unavoidable excess iron in the material limited its upper critical field, possibly due to interaction between mobile and localized electrons (known as the Kondo effect).

Why is this important?

An important goal in the search for new superconductors is to find one with the ability to carry currents with no resistance even in the presence of high magnetic fields. A material with this property could be used to build high-field magnets, store energy and to build high-speed trains.

Who did the research?

M.B. Salamon¹, N. Cornell², M. Jaime³, F. Balakirev³, A. Zakhidov¹, J. Huang⁴, H. Wang⁴

¹Dep. Of Physics, UT Dallas ²Naval Surface Warfare Center, Corona Div. ³MPA-CMMS, LANL ⁴Dept. Mat. Sci., Texas A&M Univ., College Station

Why did they need the MagLab?

These studies required 60 tesla magnetic fields provided at the National High Magnetic Field Laboratory at Los Alamos National Laboratory by discharging large banks of capacitors through special coils. The peak field exists for a fraction of a second, but high speed electronics enable measurements within the short duration of the magnetic pulse.

Details for scientists

• View or download the expert-level Science Highlight, Upper Critical Magnetic Field and Kondo Effect in FeTe_0.9Se_0.1 Thin Films
• Read the full-length publication, Upper Critical Field and Kondo Effects in Fe(Te_0.9Se_0.1) Thin Films by Pulsed Field Measurements, in Sci. Rep.

Funding

This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490)

For more information, contact Chuck Mielke.