2026/07/20 by P. Rodière, J. E. Lorenzo, Q. N. Meier +2
#cond-mat.str-el
Fermi surface nesting is key to understanding the origin of the itinerant antiferromagnetic spin density wave in Chromium. At very low temperature, this density wave is destroyed above the critical pressure Pc≈10~GPa, defining a quantum critical point. Strong electron-phonon coupling induces a small phonon softening close to the H-point of the Brillouin zone as well as close to the H-point. These phonon anomalies are known as Kohn anomalies. They remain unchanged down to 50K and are known to be present in both the paramagnetic and the antiferromagnetic phases. This paper presents inelastic X-ray scattering experiments on the phonon dispersion curves under pressure, up to P=15.6~GPa far above the critical pressure Pc. The softening of the well-known phonon anomalies is still present which leads to conclude that they do not play a major role at the antiferromagnetic ordering. Based on ab-initio calculation, the robustness of the Fermi surface nesting under pressure, explain the presence of these Kohn anomalies above the critical pressure.