Quantum criticality and strange metal behavior in a pure ferromagnetic Kondo lattice

Due to the low characteristic energies, the ground state of heavy fermion compounds is tunable upon applying a non-thermal parameter such as pressure, magnetic fields or doping. In the past decades, antiferromagnetic quantum criticality and the associated unconventional superconductivity have been observed in various compounds [1, 2]. However, solid evidence for the existence of ferromagnetic quantum criticality in a pure compound is still absent; the ferromagnetic order either vanishes suddenly or converts to an antiferromagnetic order under pressure [3]. In this talk, I will briefly present our recent progresses on the ferromagnetic heavy fermion metal CrRh6Ge4, where a pressure-induced ferromagnetic quantum critical point is observed around 0.8 GPa, accompanied by pronounced strange metal behavior and a divergent effective mass [4]. Measurements of quantum oscillations, combined with the DFT calculations, provide evidence for localized ferromagnetism at ambient pressure [5]. Recent ARPES experiments reveal anisotropic hybridization at temperatures much higher than the Curie temperature [6], and evidences for both hybridization fluctuations and collective hybridizations are shown in the ultrafast optical spectroscopy [7].

In collaboration with Bin Shen, Yongjun Zhang, An Wang, Feng Du, Yi. Wu, Ye Chen, Zhiyong Nie, Rui Li, Xin Lu, Hanoh Lee, Chao Cao, Yang Liu, Michael Smidman, Frank Steglich (Zhejiang University), Michael Nicklas, Robert Borth (MPI-CPf), David Graf (NHMFL), Jibo Qi (UESTC), and Yashar Komijani, Piers Coleman (Rutgers University).

References:
[1] N. D. Mathur et al., Nature 394, 39 (1998).
[2] Z. F. Weng et al., Rep. Prog. Phys. 79, 094503 (2016)
[3] M. Brando et al., Rev. Mod. Phys. 88, 025006 (2016) and references therein.
[4] B. Shen et al., Nature 579, 51 (2020).
[5] A. Wang et al., Science Bulletin 66, 1389 (2021)
[6] Y. Wu et al., PRL 126, 216406 (2021)
[7] Y. H. Pei et al., PRB 103, L180409 (2021)