Structure of the superconducting high-pressure phase of Sc3CoC4

Abstract

We investigate pressure-induced structural changes to the Peierls-type distorted low-temperature phase of the low-dimensional Sc 3 CoC 4 as a possible origin of its pressure-enhanced superconductivity. By means of cryogenic high-pressure x-ray diffraction experiments we could reveal subtle, but significant structural differences between the low-temperature phase at ambient and elevated pressures. We could thus establish the structure of the superconducting phase of the title compound, which interestingly still shows the main features of the Peierls-type distorted low-temperature phase. This indicates that in contrast to other low-dimensional materials a suppression of periodic structural distortions is no prerequisite for superconductivity in the transition-metal carbide.

HTD2: a single-crystal X-ray diffractometer for combined high-pressure/low-temperature experiments at laboratory scale

“…It has been shown that the complex carbide Sc 3 CoC 4 becomes a volume superconductor at a transition temperature T c of 4.5 K under only modest hydrostatic pressures (p ! 0.5 GPa) (Wang et al, 2016;Langmann et al, 2021). At the Eickerling et al, 2013;Langmann et al, 2021).…”

“…0.5 GPa) (Wang et al, 2016;Langmann et al, 2021). At the Eickerling et al, 2013;Langmann et al, 2021). Yet, previously published structural data were collected at $4 GPa and 37 K and therefore still above the T c of the compound (Langmann et al, 2021).…”

“…Such an automatic crystal re-centering is essential for temperature scans over wide temperature ranges without user intervention. An application example is the tracking of superstructure reflection intensities for the transition metal carbide Sc 3 CoC 4 over temperature ranges from $20 to 300 K at different applied pressures (Langmann et al, 2021). Another application may be the temperature-dependent study of lattice parameters, yet with limited precision in comparison with dedicated instruments (Gałdecka, 2011;Parrish et al, 2011;Toby, 2019); see the supporting information for further details.…”

“…Masking of frame pixels is accomplished by assignment of a negative intensity value (À1.0) to mark them for removal in the subsequent data integration process. A range of the masking capabilities of the program has already been employed successfully in the determination of the LT/P structure of Sc 3 CoC 4 (Langmann et al, 2021).…”

“…At the Eickerling et al, 2013;Langmann et al, 2021). Yet, previously published structural data were collected at $4 GPa and 37 K and therefore still above the T c of the compound (Langmann et al, 2021). This makes structural investigations under simultaneous LT/HP conditions in the bulk-superconducting regime of Sc 3 CoC 4 (T 4.5 K; p !…”