Variation of electronic phases in (R1R2DCNQI)2Ag: systematic change of the one-dimensional band by chemical substitution of R1 and R2

The width and dimensionality of the quasi-one dimensional electronic band of (R1,R2-DCNQI)2Ag are controlled by substitution of R1/R2 (R1/R2=Me/Me, Br/Br, Br/I, I/I). Electrical resistivity, magnetic susceptibility, and NMR measurements have been performed to characterize the spin/charge states in this family. We observed a systematic change from the well-known spin-Peierls state in the Me/Me salt to the spin gapless Wigner crystal state in the I/I salt corresponding to the band parameters. Substitution of R1 and R2 in (R1,R2-DCNQI) 2Ag successfully controls the interchain and intrachain transfer integrals of the quarter-filled π band.