@article{XuShimizuGuterdingetal.2023, author = {Xu, Han-Xiang and Shimizu, Makoto and Guterding, Daniel and Otsuki, Junya and Jeschke, Harald O.}, title = {Pressure evolution of electronic structure and magnetism in the layered van der Waals ferromagnet CrGeTe3}, series = {Physical Review B}, journal = {Physical Review B}, number = {Vol. 108}, publisher = {American Physical Society}, doi = {https://doi.org/10.1103/PhysRevB.108.125142}, pages = {15}, year = {2023}, abstract = {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. CrGeTe3 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 CrGeTe3 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 CrGeTe3. 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 CrGeTe3.}, language = {en} } @article{HanXiangGuterding2025, author = {Han-Xiang, Xu and Guterding, Daniel}, title = {Incommensurate spin fluctuations and competing pairing symmetries in La3⁢Ni2⁢O7}, series = {Physical Review B}, volume = {112}, journal = {Physical Review B}, number = {17}, publisher = {American Physical Society}, doi = {10.1103/f6nj-34th}, pages = {8}, year = {2025}, abstract = {The recent discovery of superconductivity in the bilayer Ruddlesden-Popper nickelate La3⁢Ni2⁢O7 under high pressure has generated much interest in the superconducting pairing mechanism of nickelates. Despite extensive work, the superconducting pairing symmetry in La3⁢Ni2⁢O7 remains unresolved, with conflicting results even for identical methods. We argue that different superconducting states in La3⁢Ni2⁢O7 are in close competition and highly sensitive to the choice of interaction parameters as well as pressure-induced changes in the electronic structure. Our study uses a multiorbital Hubbard model, incorporating all Ni 3⁢𝑑 and O 2⁢𝑝 states. We analyze the superconducting pairing mechanism of La3⁢Ni2⁢O7 within the random phase approximation and find a transition between 𝑑-wave and sign-changing 𝑠-wave pairing states as a function of pressure and interaction parameters, which is driven by spin fluctuations with different wave vectors. These spin fluctuations with incommensurate wave vectors cooperatively stabilize a superconducting order parameter with 𝑑𝑥2-𝑦2 symmetry for realistic model parameters. Simultaneously, their competition may be responsible for the absence of magnetic order in La3⁢Ni2⁢O7, demonstrating that magnetic frustration and superconducting pairing can arise from the same set of incommensurate spin fluctuations.}, language = {en} }