» Investigating Innovative Superconducting Materials: Reaching for Room-Temperature Superconductivity

 

Take the tour of Advanced Physics Laboratory!

The primary direction of major research, and our first stop on the tour, relates to searching for high temperature superconductivity in oxy-chalcogens. In 2005, the Senior Research Scientist and Director of APL, Dr. Armen Gulian, together with colleagues at NRL, discovered indications of very high temperature superconductivity in laser-processed Sr2RuO4. Subsequent Auger analysis revealed presence of sulfur, and for this reason, exploration of laser-processed chalcogen-doped Strontium Ruthenates is also on our agenda.

 

Laboratory set-up for processing ceramic samples using powerful, picosecond laser pulses.

Action from very short laser pulses can create unique conditions in novel materials, such as temperature and pressure found in the depth of a star. These conditions may move the experimental substance to a new, and hopefully metastable, state, so that after very fast cooling, the substance will remain in this new state. A diamond, for example, is similarly made from carbon, and the potential benefit from room-temperature superconductors will be just as, if not more, valuable in the near future.

 

Almost seven hundred samples are prepared for subsequent laser treatment.

Experiments are carefully conducted in a sterile environment to reassure compositions and repeatability.
 

Mixing precalculated and weighted powders.

Here is where the ceramic synthesis begins.
 

Some compositions require very high-temperature treatment in our high vacuum furnace.

This is an extremely important link in synthesis of novel materials.
 

Thermogravimetric analysis with mass spectrometry greatly facilitates our research.

We use this equipment to determine at which temperature our new composition melts, evaporates, emanates components (even telling us what has emanated!) or absorbs molecules from a surrounding gas, or suffers phase transition. Furthermore, we can readily determine whether or not these processes are reversible.
 

Other compositions require additional, high-temperature treatment, but in an oxygen atmosphere.

This particular furnace can reach temperatures as high as 1,500 °C (2,732 °F)!
 

Crystalline structure of samples is determined via this X-ray diffractometer.

The data obtained by this old, German-quality instrument are being further processed via Rietveld refinement.

 

Low temperature measurements using closed cycle cryostat.

Superconductivity reveals itself in measurements of resistivity being performed in this system (we can measure five pellets at once). The cryostat is fiber-wired (noticeable in the white-taped region), for the purpose of performing optical experiments with superconductors and other objects of interest.

 

Measurement of magnetic properties in SQUID Magnetometer down to 0.3K temperatures.

This is a highly sensitive tool for distinguishing existence of Meissner effect in superconductors, and confirm superconductivity itself.
 

This Hitachi SU-3500 microscope is equipped by Oxford Instruments EDX and WDX tools, allowing for additional compositional analysis and morphology.

This year, we are adding an OI EBSD tool to this system, which will make it capable of determining a samples' structure at the microlevel.
 

The morphology and composition of samples...

Sometimes, the morphology of samples is especially peculiar. Nevertheless, together, we are enthusiastically pursuing our goal of room-temperature superconductivity by investigating innovative superconducting materials.

Continue to the next section of our tour: Exploring Novel Quantum Effects and Devices.

Our recent interest was in single-flux quantum (SFQ) physics in weakly-coupled superconductor-normal metal-superconductor (SNS) Josephson junctions. We modeled these junctions is a planar geometry, where current flows in along one superconducting bank, moves along it, while crossing the initially normal region, which is converted in a weaker superconductor by proximity effect, and flows back and out along the next bank.

Abrikosov vortices/single flux quanta are being generated at the applied DC current, if its value is above the certain threshold. These vortices move and exit the junction, and generate a voltage pulse at the moment of escape. Green arrows indicate the electric vector.

Reversely, if the junction is biased below the critical current value, then a pulse generated by an SFQ signal can launch an Abrikosov vortex, which will move along the junction and exit it, emitting the same type of signal which initiated it.