Inelastic X-Ray Scattering from Phonons

Peierls-type structural phase transition in the low-dimensional superconductor Sc3CoC4

“…Among the best studied representatives are the charge-density-wave (CDW) compounds [34][35][36][37][38][39] and the binary A15 compounds [105,106] displaying low-dimensional and three-dimensional structural motifs, respectively. Similar to our results for Sc 3 CoC 4 above, many of these superconducting materials have been found to undergo phonon softening processes towards their structural phase transition temperatures [34,62,90,91,96,97,[105][106][107][108][109][110][111][112][113][114][115]. Furthermore, the structural and superconducting phase transitions in Sc 3 CoC 4 , CDWs and A15 compounds are susceptible to a manipulation by means of applied strain or hydrostatic pressure [34-36, 40-44, 51, 52, 57, 105, 111, 116-118].…”

“…Furthermore, the resulting low-temperature phase structures in CDW compounds like the quasi-one-dimensional K 0.3 MoO 3 [34,90,112,136], K 2 Pt(CN) 4 Br 0.3 •3.2 D 2 O (KCP) [34,108], NbSe 3 [34,137], ZrTe 3 [62,91], and (TaSe 4 ) 2 I [113], as well as the quasi-two-dimensional 2H-TaSe 2 [97] may be described as displacively modulated variants of a parent structure with incommensurate or commensurate q vector. Already above the actual transition temperature into the modulated phase all of the aforementioned materials show a regime of structural fluctuations that is characterized by the presence of distinct diffuse scattering and the critical growth of an elastic central peak in inelastic x-ray or neutron scattering spectra [34,62,90,91,97,108,112,113,136,137]. Yet, only K 0.3 MoO 3 [34,90,112] and ZrTe 3 [62,91] are affected by a simultaneous phonon softening of a non-zonecenter phonon mode close to zero energy in analogy to Sc 3 CoC 4 .…”

“…Already above the actual transition temperature into the modulated phase all of the aforementioned materials show a regime of structural fluctuations that is characterized by the presence of distinct diffuse scattering and the critical growth of an elastic central peak in inelastic x-ray or neutron scattering spectra [34,62,90,91,97,108,112,113,136,137]. Yet, only K 0.3 MoO 3 [34,90,112] and ZrTe 3 [62,91] are affected by a simultaneous phonon softening of a non-zonecenter phonon mode close to zero energy in analogy to Sc 3 CoC 4 . Phonon softening in the other CDW compounds is weaker like in KCP [34,108], (TaSe 4 ) 2 I [113], and 2H-TaSe 2 [96,97] or even completely absent like in NbSe 3 [137].…”