Magnetodielectric effects and spin-charge coupling in the spin-liquid candidateκ-(BEDT-TTF)2Cu2(CN)

M. Poirier

¹

,

Samuel Parent

²

,

Anne Marie Côté

³

et al.

Anisotropic charge dynamics in the quantum spin-liquid candidateκ−(BEDT-TTF)2Cu2(CN)3

“…21 The latter data discard the original interpretation by Abdel-Jawad and Hotta 20,26 based on the collective excitation of the intradimer electric dipole; this idea was previously also used to explain the microwave and terahertz anomalous charge behavior. 22,23 Nevertheless, the vibrational data allow for the presence of fast temporal fluctuations of charge distribution with the exchange frequency of 10 11 Hz, whose softening is predicted theoretically. 27 While fluctuating intradimer electric dipoles have been still discussed in literature as the possible source of terahertz response 64 , it is definitely clear that they cannot be invoked to explain dielectric response at low frequencies.…”

“…Similar observations were previously reported by the microwave and thermal conductivity measurements. 17,22 Confining ourselves to slow cooling rates (2-15 K/h) the data are not influenced by different cycling routes.…”

“…21 Nevertheless, the dielectric constant grows on cooling and seems to freeze at about 6 K; at this temperature also the microwave dielectric constant shows the strongest change. 22 A broad band was observed in the optical conductivity around 1 THz which grows below 60 K; it was attributed to the collective excitation of the fluctuating intradimer electric dipole. 23 In the same temperature range the spin susceptibility decreases gradually and (T 1 T ) −1 obtained from 13 C-NMR measurements increases, both indicating the development of AFM correlations.…”

“…Such a complex nature of κ-CN gives rise to an exotic charge-spin-lattice coupling yielding a mutually interconnected anomalous behavior of physical properties in charge, spin and lattice sectors. 18,[22][23][24][25]64 We want to recall the suggestion 19 that the spatially inhomogeneous magnetization with anomalous features originates from symmetry-broken sites. This might also reflect the structural properties of the anion network.…”

Power-law dependence of the optical conductivity observed in the quantum spin-liquid compoundκ-(BEDT-TTF)2Cu2(CN)Elsässer1, Wu2, Dressel3 et al. 2012Phys. Rev. B

“…9 Numerous theoretical and experimental work was performed during the last decade in order to explore mainly the thermodynamic and magnetic properties. [10][11][12][13][14][15] In the high-temperature range, the 1 H-NMR relaxation rate shows anomalies around 200 K, 8 the thermopower at 150 K, 16 microwave experiments exhibit a dielectric anomaly at 113 K, 17 while a peak in ǫ ′ (T ) occurs below 60 K in the radio-frequency range. 18 In addition, a low-temperature anomaly near 6 K has been observed in thermodynamic, 7,10 transport, 11 dielectric 17 and lattice 19 properties that has not been explained satisfactorily.…”