Interaction driven Pomeranchuk instability in the kagome compound CsTi₃Bi₅

Kagome metals of the 135 family like AV₃Sb₅ naturally display a variety of highly exotic phenomena long sought for in other correlated materials like the cuprates including spontaneous loop current formation and pronounced nematic tendencies. This general paradigm can be attributed to a combination of the inherent geometric frustration in the kagome lattice and the celebrated sublattice interference mechanism.

In this talk we report on the experimental observation of a d-wave charge Pomeranchuk instability in the novel kagome compound CsTi₃Bi₅ and provide a detailed microscopic picture of its formation. Using ARPES we uncover a spontaneous reduction of C₆ to C₂ symmetry in the electronic bandstructure without bandfolding and pinpoint the underlying groundstate by many-body calculations on a realistic ab-initio model. Our theoretical results recover the observed Fermi surface warping and reveal a charge imbalance between the in-plane d-orbitals of Ti as origin for the nematic transition opposed to previous suggestions based on FS nesting arguments.