Spin excitations in the quasi-two-dimensional charge-ordered insulator $\alpha$-(BEDT-TTF)${}_2$I${}_3$ probed via ${}^{13}$C NMR

Abstract

The spin excitations from the nonmagnetic charge-ordered insulating state of $\alpha$-(BEDT-TTF)${}_2$I${}_3$ at ambient pressure have been investigated by probing the static and low-frequency dynamic spin susceptibilities via site-selective nuclear magnetic resonance at ${}^{13}$C sites. The site-dependent values of the shift and the spin-lattice relaxation rate $1/T_1$ below the charge-ordering transition temperature ($T_{CO}\approx$ 135 K) demonstrate a spin density imbalance in the unit cell, in accord with the charge-density ratio reported earlier. The shift and $1/T_1$ show activated temperature dependence with a static (shift) gap ${\Delta }_S\approx$ 47-52 meV and a dynamic ($1/T_1$) gap ${\Delta }_R\approx$ 40 meV. The sizes of the gaps are well described in terms of a localized spin model, where spin one-half antiferromagnetic dimer chains are weakly coupled with each other.

arXiv comment22 pages, 7 figures, and 1 table

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• ${}^{13}$C NMR Study on the Charge-Disproportionated Conducting State in the Quasi-Two-Dimensional Organic Conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$
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Cited by in corpus (11)

• Anomalous Spin Correlations and Mass-Generating Excitonic Instability of Interacting Weyl Fermions
• Transport properties of organic Dirac electron system α-(BEDT-TSeF)${}_2$I${}_3$
• Interaction-induced quantum spin Hall insulator in the organic Dirac electron system $\alpha$-(BEDT-TSeF)${}_2$I${}_3$
• Chern Insulator Phase in a Lattice of an Organic Dirac Semimetal with Intracellular Potential and Magnetic Modulations
• Domain Wall Conductivity with strong Coulomb interaction of two-dimensional massive Dirac Electrons in the Organic Conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$
• Gap opening mechanism for correlated Dirac electrons in organic compounds $\alpha$-(BEDT-TTF)${}_2$I${}_3$ and $\alpha$-(BEDT-TSeF)${}_2$I${}_3$
• The metal-insulator transition in the organic conductor ${\beta }^{\prime \prime }$-(BEDT-TTF)${}_2$Hg(SCN)${}_2$Cl
• Effect of Coulomb Interaction on Seebeck Coefficient of Organic Dirac Electron System $\alpha$-(BEDT-TTF)${}_2$I${}_3$
• Possible Spin-Density Wave on Fermi Arc of Edge State in Single-Component Molecular Conductors [Pt(dmdt)${}_2$] and [Ni(dmdt)${}_2$]
• Fragment-orbital-dependent spin fluctuations in the single-component molecular conductor [Ni(dmdt)${}_2$]
• Role of hydrogen bonding in charge-ordered organic conductor $\alpha$-(BEDT-TTF)${}_2$I${}_3$ probed by ${}^{127}$I nuclear quadrupole resonance