Emergence of Superconducting Electronics

Dr S.S. Verma is a professor at Department of Physics, Sant Longowal Institute of Engineering and Technology, Sangrur, Punjab

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The electrical resistivity of a metallic conductor decreases gradually as its temperature is lowered. In ordinary conductors, this decrease is limited by impurities and other defects. So even near absolute zero, normal conductor shows some resistivity. On the other hand, in a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. Thus, an electric current flowing through a loop of superconductor can persist indefinitely with no power source.

Superconductivity has been instrumental in bagging The Noble Prize in Physics five times for findings as listed in the table given below.

Superconductors are touted as one of the greatest discoveries of quantum physics. These are already being used for magnets in MRI machines, levitation transport and many other applications. Superconductors may one day fuel superfast computers, which will, of course, benefit intelligence agencies that need to process and analyse vast quantities of data.

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Superconducting technologies may also pave the way for superior electrical grids and even magnetic levitation trains.

Magnetic levitation
Magnetic levitation

Superconducting electronics

Though low- to high-temperature superconducting materials have their own applications on the basis of superconductivity alone, semiconductors have a decade-long headstart and dominate the electronics industry as well. For a long time, scientists have talked about whether superconductors would be a viable alternative to semiconductors for advanced computing as superconductor enable lower-power, faster, radiation-hardened electronics.

Further, with a growing demand for electronics having miraculous characteristics (low noise, low loss, low dissipation, less weight, high resolution, high speed, high frequency, etc), use of electronic and superconductivity properties of materials—together known as ‘superconducting electronics’ or ‘electronics with superconductors’—is turning to be a field with varied applications, including superconducting circuits, superconducting quantum interference devices (SQUIDS) magnetometers, current limiters and electronic filters.

Superconducting electronics is of great interest for several niche applications, like ultrafast routers for communication networks, analogue-to-digital converters working in the microwave field and ultra-sensitive digital receivers, which have no counterpart in the semiconductor world.

Scientists across the world are investigating superconducting materials that could transform electronics in much the same way as silicon-based semiconductors did.

Superconducting materials offer less resistance than semiconductors, so currents flow much faster. Researchers intend to build software applications that will make it easier to design and develop superconducting networks to power future supercomputers capable of much faster processing with lower energy requirements.

Tools are needed to reduce the time and cost to design superconductor-based circuits, potentially revolutionising the computer and electronics industry. Therefore, to advance the science of superconducting, researchers have begun to build electronic design automation and technology computer-aided design (TCAD) tools that will make it simpler to blueprint circuits based on superconducting materials.

The programme’s short-term goal is to significantly reduce design time and increase the reliability of designs for complex circuits made of superconducting materials. The longer-term goal is to achieve a full, integrated design automation chain for digital-analogue hybrid circuits. By making it faster and easier to design such circuits, researchers intend to spur the widespread adoption of superconductor technologies.

Ultimately, the availability of design tools may foster very-large-scale integrated design of superconducting electronics, which can include millions or even hundreds of millions of components on a single chip.

Building tools For Superconductor Materials

Physicists found a way to control electrical transport through a superconducting material by building a device within it. Called Josephson junction, the device is analogous in function to the transistor in semiconductor electronics. It’s composed of two superconducting electrodes separated by about one nanometer—a billionth of a meter.

Circuits built from Josephson junctions are called SQUIDS, and used for detectors of extremely small magnetic fields, that are more than ten billion times smaller than Earth’s. However, these devices require low temperatures to operate, typically just 4 degrees above absolute zero. This requires intricate and costly cooling systems.

Nearly three decades have passed since the discovery of the first high-temperature superconductor, but progress in building electronic devices using these materials has been very slow, because process control at the sub-10-nanometre scale is required to make high-quality Josephson junctions out of these materials.

Further developments led to ceramic materials that become superconducting—that is, lose all resistance to electricity—at temperatures that can be easily achieved in the laboratory with liquid nitrogen. Discovery of high-temperature superconductivity has set off an intense effort to develop new kinds of electronics and other devices with these new materials.
In yet another development, physicists have found a new way to control the transport of electrical currents through high-temperature superconductors. Their achievement paves the way for the development of sophisticated electronic devices that are capable of allowing scientists or clinicians to non-invasively measure tiny magnetic fields in the heart or brain, and improve satellite communications.

 

This new approach will have a significant and far-reaching impact in medicine, physics, materials science and satellite communications. It will enable development of a new generation of superconducting electronics covering a wide spectrum, ranging from highly sensitive magnetometers for biomagnetic measurements of the human body to large-scale arrays for wideband satellite communications. In basic science, it could contribute to unravelling the mysteries of unconventional superconductors and play a major role in new technologies such as quantum information science.

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