Isotope effect on the Peierls transition temperature of TTF-TCNQ

Cooper, J. R.; Lukatela, Jagoda; Miljak, M.; Fabre, J.M.; Giral, L.; Aharon-Shalom, E.

doi:10.1016/0038-1098(78)90309-5

Cited by 17 publications

(4 citation statements)

References 30 publications

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“…A large contribution from intramolecular vibrations to the total electron±phonon coupling is not necessarily in contradiction with the fact that X-ray and neutron-scatterin g results are well explained by considering only rigid molecular motions [29,30,94]: the frequencies of intramolecular vibrations are much higher than external mode frequencies, the corresponding displacements in the Peierls state therefore much smaller, too small to be observed in scattering experiments. The importance of intramolecular modes in the Peierls transition is also in agreement with the observation of a positive isotope e ect in TTF±TCNQ [137], which is expected if high-frequency phonons play a role [138].…”

Section: Origin Of Phase Transitionssupporting

confidence: 81%

Organic conductors and superconductors

Jérôme¹,

Schulz²

2002

Advances in Physics

103

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Section: Origin Of Phase Transitionssupporting

confidence: 81%

Organic conductors and superconductors

Jérôme¹,

Schulz²

2002

Advances in Physics

103

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“…n Both normal and N 15 -substituted crystals were used, the latter because they have been found previously to show particularly sharp phase transitions. 7 Standard low-frequency ac resistivity and high-pressure techniques were employed, 12 using He gas as the pressure transmitting medium up to 8 kbar, and either isopentane or a mixture of isopentane and isoamyl alcohol above. Improvements in the cryogeny made possible much slower cooling and warming rates which effectively eliminated thermal lag between sample and temperature sensor (Cu-Constantan thermocouple inside the pressure cell in the range of the transitions).…”

mentioning

confidence: 99%

Pressure Dependence of the Phase Transitions in Tetrathiafulvalene-Tetracyanoquinodimethane (TTF-TCNQ): Evidence for a Longitudinal Lockin at 20 kbar

1978

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We report the pressure dependence of the three phase transitions in TTF-TCNQ as determined by resistivity measurements. There is only one transition above 15 kbar, and we find a 4-kbar regime centered at 20 kbar where the transition temperature peaks (the distortion temperature T d = 71 K at 20 kbar), and the transition is first order. We suggest that there is a commensurate x3 superlattice in this pressure regime resulting from an increase in charge transfer to §.Previous high-pressure conductivity measurements of TTF-TCNQ 1 " 3 were performed before structural information on the sequence of three phase transitions now observed became available, although some of the first evidence for more than one transition in this compound came from these experiments. 1 ' 2 In the present work we have followed all three transitions in the pressure range up to 33 kbar by measurements of the stackingaxis resistivity,. Our results are in broad agreement with the previous investigations, although we have been able to assemble a more detailed phase diagram.X-ray and neutron diffraction experiments on the phase transitions at 53, 49, and 38 K are reviewed by Comes. 4 EPR, 5 C 13 NMR, 6 and isotopeeffect 7 experiments indicate that the TCNQ stacks distort at 53 K, and that the lower transitions are associated with the TTF stacks. The presence of 4k F scattering has been taken as evidence for the importance of Coulomb correlations. 8 " 10 These are more important on the TTF stacks, 5 since the TTF bandwidth is appreciably smaller than that of the TCNQ. n Both normal and N 15 -substituted crystals were used, the latter because they have been found previously to show particularly sharp phase transitions. 7 Standard low-frequency ac resistivity and high-pressure techniques were employed, 12 using He gas as the pressure transmitting medium up to 8 kbar, and either isopentane or a mixture of isopentane and isoamyl alcohol above.

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“…129 The very fast and strong response of reflection of microwaves on illumination of partly deuterated [2,5-DMe-DCNQI] 2 Cu allows the design of fast switches. [131][132][133][134] and cation radical salts [135][136][137][138] revealed the expected small secondary deuterium effect on phase transition and transition tempera- tures to superconductivity, respectively. Deuteration of [2,5-DMe-DCNQI] 2 Cu, however, provokes an unprecedented dramatic effect, as demonstrated in Figure 9.…”

Section: Pressure Dependence Of Conductivitymentioning

confidence: 95%

“…Deuterated [2,5-DMe-DCNQI] Copper Salts. Apart from DCNQI chemistry, deuteration of some CT complexes − and cation radical salts − revealed the expected small secondary deuterium effect on phase transition and transition temperatures to superconductivity, respectively. Deuteration of [2,5-DMe-DCNQI] 2 Cu, however, provokes an unprecedented dramatic effect, as demonstrated in Figure .…”

Section: 23 Specific Properties Of [25-dme-dcnqi]2cu121mentioning

confidence: 99%