@article{0d9e74f529d849199be4fe73ce50b03d,
title = "Sound velocity measurements on (TMTSF)2PF6",
abstract = "We have measured the velocity of sound for (TMTSF)2PF6 along the highly conducting b-axis by observing resonances in flexural and elongation modes of single crystals. Upon cooling large changes due to thermal expansion are observed as with TTF-TCNQ. In contrast with magnetic susceptibility measurements, the sound velocity clearly shows the opening of a gap at the metal insulator transition at 12 K. From the change in sound velocity at the transition we estimate the electron-phonon coupling c constant as λ ≈ 0.014 for long wavelength acoustic phonons.",
author = "Chaikin, {P. M.} and T. Tiedje and Bloch, {A. N.}",
note = "Funding Information: THE PROPERTIES of the organic charge transfer salt tetramethyl-tetraselenafulvalene-phosphorus hexafluoride (TMTSF)2PF e have been a subject of substantial interest. There is a metal insulator transition (variously quoted as 18-12.5 K) \[1--4\]a t ambient pressure which can be suppressed by application of modest pressures {"}{"} 10 Kbar resulting in a low temperature superconducting state \[5, 6\]. At ambient pressure, magnetic susceptibility measurements \[2, 3, 7\] have not detected the opening of a charge density wave (CDW) gap as has been observed in related compounds. Instead, the anisotropy in the susceptibility suggests that (TMTSF)~PF6 is a spin density wave (SDW) system. Moreover, in the region of the metal-insulator transition the conductivity and ESR susceptibility are strongly dependent on applied electric field in the mV cm -1 range \[2, 4\]. In this paper, we report sound velocity measurements on (TMTSF)2PF6 from room temperature to 4.2 K. From the lattice stiffening which results from loss of electron screening at the metal insulator transition we are able to determine that the transition temperature is 12 K for our samples in agreement with measurements of the logarithmic derivative of the resistance. An electronic gap opens at this transition with BCS-like temperature dependence. From the change in sound velocity through the transition we are able to calculate the electron-phonon coupling constant for long-wavelength longitudinal phonons. We also * A.P. Sloan Foundation Fellow. Research supported by NSF DMR 79-08560.",
year = "1982",
month = mar,
doi = "10.1016/0038-1098(82)91128-0",
language = "English (US)",
volume = "41",
pages = "739--742",
journal = "Solid State Communications",
issn = "0038-1098",
publisher = "Elsevier Ltd",
number = "10",
}