For years, physicists have predicted that the fundamental quantum states superconductivity and superinsulation occur as mirrored reflections of one another, and a new study published in Scientific Reports has validated this prediction.
The team behind the study said their confirmation might lead to the advancement of supersensitive and energy-efficient detectors and logical switches for next-generation digital technologies.
The study team observed the transformation, which they dubbed the ‘charge Berezinskii-Kosterlitz-Thouless (BKT)’ transition, in a thin film of superconducting niobium-titanium nitrite. The transition observed by the study team is the mirror-image of a transition scientists have documented numerous times in superconducting materials, now known as the ‘vortex BKT’ transition.
The experiments carried out by our team conclusively establish the existence of the superinsulating state and the validity of its foundational concepts, including the fundamental concept of charge-vortex duality.
Valerii Vinokur, Research Fellow - US Department of Energy’s Argonne National Laboratory
The duality principle in physics states that fundamental pair of phenomena exclude one another but act as two sides of the same coin. A popular example of this duality is the wave-particle duality of light seen in quantum physics. Superinsulating and superconducting materials, which are polar opposites, signify the duality between electric and magnetic effects. While superconductors transfer electric current without a decrease in power, superinsulators completely disrupt the movement of charges under an applied voltage. To put it another way, superconductors have infinite conductance, and superinsulators have infinite resistance.
The most recent finding expands on work published in 2008 by the same team of researchers that was able to experimentally identify the existence of the superinsulating state, while also indicating it mirrors the behavior that takes place in the superconducting state based on a fundamental quantum concept, the uncertainty principle. Theoretical physicists at CERN and the University of Geneva had projected the existence of this phenomenon in 1996.
“The behavior we have demonstrated is exactly the behavior that was predicted and expected,” Vinokur said.
One potential research path for the study team is to boost the temperature at which their thin film converts into the superinsulating state. The transition temperature used in the study was between 100 and 200 millikelvins, just a fraction of a degree more than absolute zero. Increasing that transition temperature to 4 Kelvin would be considered an engineering breakthrough.
“This means that we could use these materials in space because 4 Kelvin is the temperature of space,” Vinokur said. Potential space-based applications include detectors for recording electromagnetic radiation and other cosmic phenomena, as well as switches for electronics, like energy-saving diodes.
The study team named the transition Berezinskii-Kosterlitz-Thouless after scientific icons Vadim Berezinskii, Michael Kosterlitz and David Thouless. Kosterlitz and Thouless worked together in the early 1970s to formulate their idea of topological phase transitions, which are very unlike the phase transitions commonly understood in physics at the time. These phase transitions occur as a distinct change in the state of matter like ice melting to water, at a certain temperature. Topological phase transitions, however, are clear changes in the qualities of the system without any overt material shifts.
Working separately from Kosterlitz and Thouless, Berezinskii developed comparable theories, ultimately leading to several findings on vortex BKT transitions in thousands of superconductivity tests. However, until now, researchers had never definitively identified the mirror-image of the vortex BKT transition, the charge BKT transition, on the superinsulating part of the superconductor-insulator transition.
The 2016 Nobel Prize in physics was awarded to Kosterlitz, Thouless and Duncan Haldane for “theoretical discoveries of topological phase transitions and topological phases of matter,” having created the advanced mathematical techniques required to explain the phase transitions that take place in strange states of matter, including superconducting materials and thin magnetic films.
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