Unconventional dual 1D-2D quantum spin liquid revealed by $ab$ $initio$ studies on organic solids family

TL;DR

This study uses ab initio calculations to reveal a dual 1D-2D quantum spin liquid state in organic solids, showing dimensional reduction and spin fractionalization, advancing understanding of quantum spin liquids in organic materials.

Contribution

First comprehensive ab initio study of multiple organic compounds revealing a dual 1D-2D quantum spin liquid with dimensional reduction and spin fractionalization.

Findings

Reproduces experimental phase diagram without adjustable parameters.

Identifies 1D nature of QSL with algebraic and exponential decay of spin correlations.

Reveals duality bridging 1D and 2D quantum spin liquids.

Abstract

Organic solids host various electronic phases. Especially, a milestone compound of organic solid, $\beta'$-$X$[Pd(dmit)$_2$]$_2$ with $X$=EtMe$_3$Sb shows quantum spin-liquid (QSL) properties suggesting a novel state of matter. However, nature of the QSL has been largely unknown. Here, we computationally study five compounds comprehensively with different $X$ using 2D $ab$ $initio$ Hamiltonians and correctly reproduce experimental phase diagram with antiferromagnetic order for $X$=Me$_4$P, Me$_4$As, Me$_4$Sb, Et$_2$Me$_2$As and a QSL for $X$=EtMe$_3$Sb without adjustable parameters. We find that the QSL for $X$=EtMe$_3$Sb exhibits 1D nature characterized by algebraic decay of spin correlation along one direction, while exponential decay in the other direction, indicating dimensional reduction from 2D to 1D. The 1D nature indeed accounts for the experimental specific heat, thermal conductivity and magnetic susceptibility. The identified QSL, however, preserves 2D nature as well consistently with spin fractionalization into spinon with Dirac-like gapless excitations and reveals duality bridging the 1D and 2D QSLs.