Within topological materials, one may expect startlingly disparate quantum states of matter depending on the degree of correlations that the constituent particles possess.
The regime of strong correlations provides an opportunity to realize correlation-driven topological states, while also presenting many challenges. In recent years, there has been considerable progress that has been made in heavy fermion systems, both theoretically [1,2,3] and experimentally [4,5,6].
In this talk, I introduce the Weyl-Kondo semimetal, a topological semimetal phase with prototypical strong correlations.
The theoretical investigation has centered on a nonsymmorphic Anderson/Kondo lattice model that preserves time-reversal symmetry while breaking inversion symmetry [1, 2].
We found a robust strongly correlated Weyl semimetal phase, where Weyl nodes are pinned to the Fermi energy by, and form directly from the Kondo effect.
I will also touch upon the concurrent experimental effort, which has centered on the non-centrosymmetric, non-magnetic, and non-symmorphic heavy fermion compound Ce$_3$Bi$_4$Pd$_3$ [4,5]; the unique signatures of the Weyl-Kondo semimetal phase appear in a $T^3$ specific heat and a giant spontaneous Hall response.
Both in the theoretical model and in experiments, the Zeeman coupling has been found to provide extreme topological tunability [3,6]. I will conclude the talk by discussing the prospect for future progress along this general direction.
[1] H.-H. Lai, S. E. Grefe, S. Paschen, and Q. Si, Proc. Natl. Acad. Sci. U.S.A. 115, 93 (2018).
[2] S. E. Grefe, H.-H. Lai, S. Paschen, and Q. Si, Phys. Rev. B, 101, 075138 (2020).
[3] S. E. Grefe, H.-H. Lai, S. Paschen, Q. Si., arXiv:2012.15841 (2020).
[4] S. Dzsaber, L. Prochaska, A. Sidorenko, G. Eguchi, R. Svagera, M. Waas, A. Prokofiev, Q. Si, and S. Paschen, Phys. Rev. Lett. 118, 246601 (2017).
[5] S. Dzsaber, X. Yan, M. Taupin, G. Eguchi, A. Prokofiev, T. Shiroka, P. Blaha, O. Rubel, S. E. Grefe, H.-H. Lai, Q. Si, and S. Paschen., Proc. Natl. Acad. Sci. U.S.A. 118, 8 (2021).
[6] S. Dzsaber, D. A. Zocco, A. McCollam, F. Weickert, R. McDonald, M. Taupin, X. Yan, A. Prokofiev, L. M. K. Tang, B. Vlaar, et al., arXiv:1906.01182 (2019).