Spectroscopic study of isostructural charge-transfer salts: Non-metallic DMTTA-BF4 and metallic DMTSA-BF4

Jianyong Ouyang, Jian Dong, Kyuya Yakushi, Kazuo Takimiya, Tetsuo Otsubo

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We present the polarized reflection spectra of non-metallic DMTTA-BF4 and the isostructural metallic DMTSA-BF4. From these spectra, both compounds were regarded as quasi-one-dimensional conductors. From the analysis of these spectra we show that DMTTA-BF4 is a Mott insulator with U/4t ≈ 0.8-1.2 and DMTSA-BF4 is a weakly correlated metal with structural fluctuation near the room temperature. Resistivity, thermopower, and ESR are consistent with the above picture, and demonstrate the phase transitions at ca. 100K for DMTTA-BF4 and at ca. 150K for DMTSA-BF4. The low-temperature reflection spectra of both compounds strongly suggest the breaking of screw-axis symmetry along the conducting axis. These phase transitions are regarded as the spin Peierls transition (DMTTA-BF4) and Peierls (DMTSA-BF4) transition. Assuming a dimerized stack, we estimate the transfer integrals t1 and t2 as 0.25 and 0.21 eV from the 10K spectrum of DMTSA-BF4. The coupling constants of molecular vibration of DMTSA with the inter-molecular charge-transfer excitation are obtained analyzing the polarized reflection spectrum of DMTSA-CIO4 having a dimerized structure.

Original languageEnglish
Pages (from-to)3708-3716
Number of pages9
Journaljournal of the physical society of japan
Volume68
Issue number11
DOIs
Publication statusPublished - 1999 Jan 1
Externally publishedYes

Keywords

  • Band parameter
  • DMTSA
  • DMTTA
  • Organic conductor
  • Peierls transition
  • Reflection spectrum
  • Spin Peierls transition

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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