Physicists hit major milestone in advancing superconductor applications

In their study titled "Creation, stabilization, and investigation at ambient pressure of pressure-induced superconductivity in Bi_0.5Sb_1.5Te₃," published in the Proceedings of the National Academy of Sciences, professors Liangzi Deng and Paul Ching-Wu Chu of the UH Department of Physics set out to see if they could push BST into a superconducting state under pressure -- without altering its chemistry or structure.

"In 2001, scientists suspected that applying high pressure to BST changed its Fermi surface topology, leading to improved thermoelectric performance," Deng said. "That connection between pressure, topology and superconductivity piqued our interest."

"As materials scientist Pol Duwez once pointed out, most solids that are crucial to industry exist in a metastable state," Chu said. "The problem with that is many of the most exciting superconductors only work under pressure, making them difficult to study and even harder to use in practical applications."

That's where Deng and Chu's breakthrough comes in.

Using a technique they developed called the pressure-quench protocol (PQP), described in an October UH news release, Deng and Chu successfully stabilized BST's high-pressure-induced superconducting states at ambient pressure -- meaning no special high-pressure environments needed.

Why does this matter? It opens up a whole new way to retain valuable material phases that usually only exist under pressure for fundamental research and practical application.

"This experiment clearly demonstrates that one may stabilize the high-pressure-induced phase at ambient pressure via a subtle electronic transition without a symmetry change, offering a novel avenue to retain the material phases of interest and values that ordinarily exist only under pressure," Chu said. "It should help our search for superconductors with higher transition temperatures."

"Interestingly, this experiment revealed a novel approach to discovering new states of matter that do not exist at ambient pressure originally or even under high-pressure conditions," Deng added. "It demonstrates that PQP is a powerful tool for exploring and creating uncharted regions of material phase diagrams."