Accelerated Supercurrents Give Scientists Access To “Forbidden” Light

In what is defined as “a fundamental discovery of quantum matter,” a group of American scientists have retrieved forbidden light discharges that could one day help to advance quantum technologies.

 

To make their discovery, the researchers focused trillions of light pulses every second in the direction of pairs of electrons (called Cooper pairs) that were flowing through a superconductor at a tremendously cold temperature. This triggered the electron pairs in the “supercurrents” (an electrical current that moves without energy loss) to accelerate. When observed, the light discharged by the accelerated electron pairs had twice the frequency of the received pulsed light, called “second harmonic light emissions.”

 

“These second harmonic (terahertz) emissions are thought to be forbidden in superconductors,” Jigang Wang, a lecturer of physics and astronomy at Iowa State University, described in a statement. “This is against the conventional knowledge.”

 

Stated in a paper published in Physical Review Letters, the ground-breaking technique also unlocked another phenomenon.

 

“The forbidden light gives us access to an interesting class of quantum phenomena – that's the energy and particles at the small measure of atoms – called forbidden Anderson pseudo-spin precessions,” Ilias Perakis, a co-author and lecturer at the University of Alabama at Birmingham, clarified.

 

Named after the late Nobel Laureate Philip W. Anderson, Anderson pseudo-spins were suggested to define the superconducting state. In this latest research, the precession of these twisted pseudo-spins broke the symmetry of the method of electrons in the Niobium-tin superconductor, thus allowing the “forbidden” light to be discharged.

 

 

The procession (far right) of Anderson pseudo-spins broke the symmetry of the system and led to the emission of "forbidden light". Jigang Wang/Iowa State University

“The determination of symmetry breaking in superconducting states is a new cutting edge in both fundamental quantum matter innovation and practical quantum information science,” Wang told. “This will be useful in the improvement of future quantum computing approaches and electronics with high speeds and low energy consumption."

 

“Finding means to control, access and operate the special characteristics of the quantum world and connect them to real-world issues is a key scientific push these days,” Perakis added.

 

Wang and Perakis will be amongst many researchers in the coming years digging further into the exotic and magical world of quantum.

References:

https://phys.org/news/2020-05-scientists-supercurrents-access-forbidden-quantum.html

https://www.science20.com/news_staff/forbidden_light_in_the_quantum_world-248070