When Heike Kamerlingh Onnes discovered superconductivity he most likely had no idea what he was revealing. Superconductivity is an amazing phenomenon to witness. A typical demonstration involves a disk cooled using liquid nitrogen hovering over a track of magnets. This demonstration always gathers a crowd at our Faraday Holiday Shows we put on at Rutgers Physics Lecture Hall. Superconductors have the potential to be world-changing if we can make them practical.
Superconductors are able to transmit electricity with 100% efficiency. There are many other possible applications of these materials including electric circuitry, medical equipment, high energy particle detectors, and electric motors. Materials are kept at extremely low temperatures in order to become superconductors. This makes real-world applications inefficient. Scientists have been theorizing about room temperature superconductors for a long time. Recently the search for them was proven to be on the right path.
In September of 2019, a research team published a research paper in Nature reporting they had achieved superconductivity of Lanthanum Hydride compounds at 250K. This is the highest confirmed temperature recorded to date. This achievement is a reassuring confirmation of theoretical room temperature superconductivity.
In order to achieve superconductivity at a higher temperature, the team compressed a sample of Lanthanum at pressures of a million times atmospheric pressure. The researchers used a device called a Diamond Anvil Cell in order to carry out the experiment. Using a thin metal foil to encase the sample, two flattened diamond plates are used to compress the Lanthanum. This type of system has a limitation of the type of data that can be recorded due to the small sample size of 0.01 millimeters across. One of the testing methods of superconductors is electrical measurement. This involves connecting the sample to electrical leads which must remain independent from the foil which the sample is contained in. The team uses an insulator in order to prevent interference between the foil and the sample when measuring the electrical information.
Despite the difficulties of the experiment, the researchers were successful and compressed lanthanum into lanthanum hydride while confirming superconductivity at a record high temperature.
In order to declare a material as a superconductor researchers evaluate three characteristics. These are: 1) zero electrical resistance; 2) a reduction in the critical temperature under an applied magnetic field; 3) expulsion of magnetic fields from the interior of the material. This expulsion of magnetic fields is known as the Meissner effect. The team was able to obtain the first two characteristics of the material. The Meissner effect was not recorded because of the sample size. The researchers will require additional experimentation with larger samples in order to measure the magnetization. The material themselves must also be evaluated. If samples of the compressed material will maintain their structure at normal pressure, much like a diamond, this may be a viable option for the future of superconductors.
The implications of this research will likely drive future experiments to test other hydrogen-rich materials in order to achieve room temperature superconductivity. The results are positive and confirm a mathematical theory which predicted the pressure and temperature required. These results are a step in the direction of room-temperature superconductivity.