Superconducting Quantum Interference Devices (SQUID) Open Up Practical Applications For Superconductivity

Devices sensitive enough to detect and measure minute changes of magnetic fields, called superconducting quantum interference devices (SQUIDs), are opening up practical application of superconductivity outside the laboratory. Some applications that can benefit from using SQUIDs are magnetically levitating (maglev) trains, earthquake detectors, and even solar power cells.

Dutch physicist Heike Kamerlingh Onnes discovered superconductivity in 1911 during an experiment involving mercury and liquid helium. When a material's temperature is reduced to a certain threshold, its electrical resistance falls down to zero and the expulsion of its magnetic fields occur. Materials that can achieve superconductive are metals and ceramic materials.

The temperature at which superconductivity occurs vary from material to material. Mercury, for example, achieves superconductivity when its temperature is lowered to 4.1K.

Without electrical resistance, an electric current can persist indefinitely even without a power source. There is no power loss with superconductors and that any existing power in a superconductive wire will forever flow in it. Superconducting wires can conduct much larger currents than ordinary wire which create much more intense magnetic fields around them.

Magnetic Resonance Imaging (MRI) machines, mass spectrometers, and even particle accelerators like the Large Hadron Collider use superconducting magnets (electromagnets made from coils of superconducting wires.).

Last year, a research team at the University of Toronto induced high temperature superconductivity in a semiconductor by just using ordinary scotch tape.

Hunting Down Charge Density Waves To Solve High Temperature Superconductivity Mystery

Inside a clean room, physicists Ivan Bozovic (left) and Anthony Bollinger, Brookhaven, work on the molecular beam epitaxy system that produced the atomically perfect materials used in the study.
Credit: Brookhaven National Lab

Scientists are trying to unlock the mystery of high temperature superconductivity (HTS) by studying fluctuations (ripples of moving electrons) called charge density waves (CDW).

Objects or materials that have been super-cooled or its temperature lowered below a certain value, it achieves superconductivity. Temperatures required to achieve superconductivity usually are close to absolute zero (0 Kelvin). This means that there is no electrical resistance and there is an expulsion of magnetic fields occurring at that temperature.

This expulsion is a quantum mechanical property that is described by the Meissner effect.

As the temperature is lowered, the electrical resistance goes down as well. Below a critical temperature, the electrical resistance of a superconductor lowers down to zero. Without it, an electric current can persist indefinitely even without a power source. There is no power loss and that any existing power in a superconductive wire will forever flow in it.

Last September 2012, a team from the University of Toronto induced high temperature superconductivity in a semiconductor just by using Scotch tape. A first for physics.

Recently, researchers have developed HTS materials that would help them understand this phenomenon by recreating it and studying fluctuations within the material called charge density waves.