Anisotropic quantum criticality in CeCoIn5 from ultrafast nanocalorimeter spectroscopy

CeCoIn5 features divergence of quasiparticle mass at very low temperatures which is currently understood as a result of an antiferromagnetic quantum critical point (QCP). NMR measurements show that mass increase is cut off in a finite magnetic field at very low temperatures indicating energy scale competition near the QCP. However, these measurements do not reveal the full spectrum of quantum fluctuations and their angular anisotropy. Additionally, Heat capacity measurements are challenging at these temperatures and magnetic fields because of the strong nuclear Schottky from Indium115. We use novel nanocalorimeter spectroscopy to determine electronic heat capacity and nuclear Schottky in CeCoIn5 at ultralow temperatures. I will discuss the new results and implications for the physics of CeCoIn5.