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

K. Itoh, H. Itoh, S. Saito, I. Hosako, Y. Nakamura, H. Kishida, N. Yoneyama, T. Sasaki, S. Ishihara, and S. Iwai
Phys. Rev. B 88, 125101 – Published 3 September 2013

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 cm1 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.

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  • Received 16 May 2013

DOI:https://doi.org/10.1103/PhysRevB.88.125101

©2013 American Physical Society

Authors & Affiliations

K. Itoh1, H. Itoh1,2, S. Saito3, I. Hosako3, Y. Nakamura4, H. Kishida2,4, N. Yoneyama2,5, T. Sasaki2,5, S. Ishihara1, and S. Iwai1,2,*

  • 1Department of Physics, Tohoku University, Sendai 980-8578, Japan
  • 2JST, CREST, Sendai 980-8578, Japan
  • 3National Institute of Information and Communications Technology, Kobe 651-2492, Japan
  • 4Department of Applied Physics, Nagoya University, Nagoya 464-8603, Japan
  • 5Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

  • *Author to whom correspondence should be addressed: s-iwai@m.tohoku.ac.jp

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Vol. 88, Iss. 12 — 15 September 2013

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