Phys.org April 18, 2023
For two decades, it was believed that a possible quantum spin liquid was discovered in a synthetically produced material. In this case, it would not follow the laws of classical physics even on a macroscopic level, but rather those of the quantum world. An international team of researchers (Austria, Spain) has shown that the promising material, κ-(BEDT-TTF)2Cu2(CN)3, is not the predicted quantum spin liquid, but a material that can be described using known concepts. They were able to precisely map the spin-gapped phase through the Mott transition by ultrahigh-resolution strain tuning. Through transport experiments they revealed a reentrance of charge localization below T⋆ = 6 K associated with a gap size of 30–50 K. The negative slope of the insulator-metal boundary evidences the low-entropy nature of the spin-singlet ground state. By tuning the enigmatic ‘6K anomaly’ through the phase diagram they identified it as the transition to a valence-bond-solid phase, in agreement with previous thermal expansion and magnetic resonance studies. This spin-gapped insulating state persists at T → 0 until unconventional superconductivity and metallic transport proliferate. According to the researchers their research provides important clues for further research into these materials… read more. Open Access TECHNICAL ARTICLEÂ
Fingerprints of Mott transition and ‘6K anomaly’ in transport gap. Credit: Nature Communications volume 14, Article number: 1960 (2023)Â