Charge-Transfer Complex $κ$-(BEST)$_2$Cu$_2$(CN)$_3$ Analogous to Organic Spin Liquid Candidate

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Main Authors: Kobayashi, Takuya, Sakurai, Kent Andrew, Michimura, Shinji, Taniguchi, Hiromi
Format: Preprint
Published: 2025
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author Kobayashi, Takuya
Sakurai, Kent Andrew
Michimura, Shinji
Taniguchi, Hiromi
author_facet Kobayashi, Takuya
Sakurai, Kent Andrew
Michimura, Shinji
Taniguchi, Hiromi
contents We report the structural, electrical, and magnetic properties of the organic conductor $κ$-(BEST)$_2$Cu$_2$(CN)$_3$ (BEST: bis(ethylenediseleno)tetrathiafulvalene; abbreviated as $κ$-BEST-CN), which is isostructural with the quantum spin liquid candidate $κ$-(ET)$_2$Cu$_2$(CN)$_3$ (ET: bis(ethylenedithio)tetrathiafulvalene; abbreviated as $κ$-ET-CN). Resistivity measurements demonstrate that $κ$-BEST-CN exhibits semiconducting behavior, governed by the same conducting mechanism as $κ$-ET-CN. Under a pressure of ~0.1 GPa, $κ$-BEST-CN undergoes a superconducting transition with an onset temperature of ~4 K. From the comparison of the critical pressures of superconductivity between $κ$-ET-CN and $κ$-BEST-CN, $κ$-BEST-CN can be regarded as a chemically pressurized analogue of $κ$-ET-CN. Therefore, $κ$-BEST-CN, in which only the effective pressure changes without altering the anion structure, is considered a valuable reference material for elucidating the enigmatic properties observed in $κ$-ET-CN. Furthermore, the spin susceptibility of $κ$-BEST-CN is slightly larger than that of $κ$-ET-CN and shows weaker temperature dependence, which cannot be explained by the localized spin model. This behavior clarifies the anomalous magnetic properties of a system with frustration near the Mott transition, serving to stimulate future theoretical research.
format Preprint
id arxiv_https___arxiv_org_abs_2507_21343
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Charge-Transfer Complex $κ$-(BEST)$_2$Cu$_2$(CN)$_3$ Analogous to Organic Spin Liquid Candidate
Kobayashi, Takuya
Sakurai, Kent Andrew
Michimura, Shinji
Taniguchi, Hiromi
Strongly Correlated Electrons
Superconductivity
We report the structural, electrical, and magnetic properties of the organic conductor $κ$-(BEST)$_2$Cu$_2$(CN)$_3$ (BEST: bis(ethylenediseleno)tetrathiafulvalene; abbreviated as $κ$-BEST-CN), which is isostructural with the quantum spin liquid candidate $κ$-(ET)$_2$Cu$_2$(CN)$_3$ (ET: bis(ethylenedithio)tetrathiafulvalene; abbreviated as $κ$-ET-CN). Resistivity measurements demonstrate that $κ$-BEST-CN exhibits semiconducting behavior, governed by the same conducting mechanism as $κ$-ET-CN. Under a pressure of ~0.1 GPa, $κ$-BEST-CN undergoes a superconducting transition with an onset temperature of ~4 K. From the comparison of the critical pressures of superconductivity between $κ$-ET-CN and $κ$-BEST-CN, $κ$-BEST-CN can be regarded as a chemically pressurized analogue of $κ$-ET-CN. Therefore, $κ$-BEST-CN, in which only the effective pressure changes without altering the anion structure, is considered a valuable reference material for elucidating the enigmatic properties observed in $κ$-ET-CN. Furthermore, the spin susceptibility of $κ$-BEST-CN is slightly larger than that of $κ$-ET-CN and shows weaker temperature dependence, which cannot be explained by the localized spin model. This behavior clarifies the anomalous magnetic properties of a system with frustration near the Mott transition, serving to stimulate future theoretical research.
title Charge-Transfer Complex $κ$-(BEST)$_2$Cu$_2$(CN)$_3$ Analogous to Organic Spin Liquid Candidate
topic Strongly Correlated Electrons
Superconductivity
url https://arxiv.org/abs/2507.21343