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arXiv · 2208.05602

Role of hydrogen bonding in charge-ordered organic conductor $\alpha$-(BEDT-TTF)$_2$I$_3$ probed by $^{127}$I nuclear quadrupole resonance

T. Kobayashi·Y. Kato·H. Taniguchi·T. Tsumuraya·K. Hiraki·S. Fujiyama
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Abstract

We present $^{127}$I nuclear quadrupole resonance spectra and nuclear relaxation of $\alpha$-(BEDT-TTF)$_2$I$_3$ that undergoes a charge-ordering transition. Only one of the two I$_3$ anion sites shows a significant differentiation in the electric field gradients across the first-order transition. The charge modulation only in the BEDT-TTF layers can not reproduce; instead, an anion-donor interaction accompanied by hydrogen bonding is necessary. The dominating source for the nuclear relaxation is the local libration of the I$_3$ anions, but an anomalous peak is detected just below the transition, as observed by $^{13}$C NMR.

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T. Kobayashi, Y. Kato, H. Taniguchi, T. Tsumuraya, K. Hiraki, S. Fujiyama. 2022-08-11. Role of hydrogen bonding in charge-ordered organic conductor $\alpha$-(BEDT-TTF)$_2$I$_3$ probed by $^{127}$I nuclear quadrupole resonance. https://doi.org/10.1103/physrevb.108.115108

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