Pressure evolution of electronic structure and magnetism in the layered van der Waals ferromagnet CrGeTe3

Layered van der Waals ferromagnets, which preserve their magnetic properties down to exfoliated monolayers, are fueling an abundance of fundamental research and nanoscale device demonstration. ${\mathrm{CrGeTe}}_{3}$ is a prime example of this class of materials. Its temperature-pressure phase diagram features an insulator-to-metal transition and a significant increase in ferromagnetic Curie-Weiss temperatures upon entering the metallic state. We use density functional theory to understand the magnetic exchange interactions in ${\mathrm{CrGeTe}}_{3}$ at ambient and elevated pressures. We calculate Heisenberg exchange couplings, which provide the correct ferromagnetic ground state and explain the experimentally observed pressure dependence of magnetism in ${\mathrm{CrGeTe}}_{3}$. Furthermore, we combine density functional theory with dynamical mean-field theory to investigate the effects of electronic correlations and the nature of the high-pressure metallic state in ${\mathrm{CrGeTe}}_{3}$.