Narrowing of phonon spectrum induced by ultrafast charge fluctuations in an organic dimer Mott insulator

Keisuke Itoh, Hirotake Itoh, S. Saito, I. Hosako, Y. Nakamura, H. Kishida, N. Yoneyama, Takahiko Sasaki, Sumio Ishihara, Shinichiro Iwai

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6 Citations (Scopus)

Abstract

We have observed the characteristic temperature dependence of the intermolecular phonon spectrum in the organic dimer Mott insulator κ-(ET)2Cu2(CN)3 exhibiting a dielectric anomaly at ∼30 K. The anomalous spectral narrowing of the 55 cm-1 phonon peak at ∼30 K was analyzed in terms of motional narrowing within the framework of a stationary Gaussian process, i.e., the phonon frequency is modulated by the ultrafast charge fluctuation. The spectral narrowing occurs because the time constant of the correlation time τc and the amplitude Δ of the frequency modulation satisfy the relation τc<1/Δ at 30 K. At temperatures below 30 K, the motional narrowing is disturbed by the increase of τc, near the charge-glass or the short-range order at 6 K. On the other hand, for temperatures above 30 K, the motional narrowing is disturbed by the increase of Δ with increasing temperature.

Original languageEnglish
Article number125101
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume88
Issue number12
DOIs
Publication statusPublished - 2013 Sep 3

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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