Speaker
Description
The CeSb magnetic phase diagram contains at least 16 different magnetic phases in the H-T plane [1] comprising different sequences of ferromagnetic and paramagnetic (001) planes stacked along the c-axis. The complexity is thought to arise from the interplay of Kondo, spin-orbit and crystal-field effects. [1, 2] Lattice modulation in the magnetic phases was also observed [3].
The phase diagram [4, 5] and the magnetic excitations [1] were thoroughly studied by neutron scattering. Recently the sensitivity of the electronic structure to the magnetic phase has been demonstrated [6] and additional magnetic excitations were found in the ordered phases [7].
While the main features of the magnetic behavior are understood and successfully modeled using effective interaction approach [8] the microscopic origin of the interactions is still puzzling [2, 7]. Here we present and discuss our investigation of the ultrafast non-equilibrium dynamics in different magnetic phases in CeSb with focus on the magnetic excitations. We confirm the presence of the recently reported [7] additional modes in the ground-state antiferromagnetic phase and show that their frequencies are magnetic-field independent. In the high-magnetic field ferromagnetic phase we identify a previously unobserved $^2$E$_{2g}$, Ce$^{3+}$ crystal-field excited state. The associated coherent oscillatory optical response can be linked to the real-time quantum evolution of the superposition state involving the ground state and the $^2$E$_{2g}$ crystal field excited state.
References
1. B Hälg and A Furrer, Physical Review B34, 6258 (1986).
2. Jang et al., Sci. Adv. 5, 7158 (2019).
3. D. F. McMorrow et al., J. Phys.: Condens. Matter 9, 1133 (1997).
4. J. Rossat-Mignod et al., Physical Review B16, 440 (1977).
5. T. Chattopadhyay et al., Physical Review B49, 15096 (1994).
6. Kuroda et al., Nat. Comm 11, 2888 (2020).
7. Y. Arai et al., Nat. Mat. 21, 410 (2022).
8. T. Kasuya et al., JMMM 90 & 91 389 (1990).
