By Josh Perry, Editor
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Scientists at Rice University (Houston, Texas) published two studies demonstrating a method for tuning quantum materials, particularly in iron selenide, for high-temperature superconductivity by altering the electron order in the material.

Researchers at Rice University are studying how to tune quantum materials to enhance high-temperature superconductivity. (Wikimedia Commons)

Researchers used orbital-selective pairing to explain the high-temperature superconductivity that had been previously documented in the material and to predict how it would impact the properties of other superconducting materials, according to a report from the university.

The simulations showed that electrons in some atomic shells are more likely to pair together and tuning electrons into specific orbitals.

“In nematic systems, there is a higher degree of order in one direction than another,” the report explained. “In a box of uncooked spaghetti, for example, the noodles are aligned longwise but disordered if viewed in the perpendicular direction.”

Researchers calculated the superconducting gap, which is the difference between the energy costs of breaking electrons in the nematic direction and the perpendicular direction. They found a significant difference between the two directions.

The research was published in Physical Review Letters and in Physical Review B. The abstract from the first report stated:

“Motivated by the recent low-temperature experiments on bulk FeSe, we study the electron correlation effects in a multiorbital model for this compound in the nematic phase using the U(1) slave-spin theory.

“We find that a finite nematic order helps to stabilize an orbital selective Mott phase. Moreover, we propose that when the d- and s-wave bond nematic orders are combined with the ferro-orbital order, there exists a surprisingly large orbital selectivity between the xz and yz orbitals even though the associated band splitting is relatively small.

“Our results explain the seemingly unusual observation of strong orbital selectivity in the nematic phase of FeSe, uncover new clues on the nature of the nematic order, and set the stage to elucidate the interplay between superconductivity and nematicity in iron-based superconductors."