Anisotropic excitonic magnetism from discrete $C_4$ symmetry in ${\mathrm{CeRhIn}}_5$

Journal Article · 28 August 2024 · Physical Review. B

DOI: https://doi.org/10.1103/PhysRevB.110.064434 · OSTI ID:2438389

Brener, D. J. ; Mallo, I. Rodriguez ; Lane, H.; Rodriguez-Rivera, J. A. ; Schmalzl, K. ; Songvilay, M.; Guratinder, K.; Petrovic, C.; Stock, C.

Anisotropy in strongly correlated materials is a central parameter in determining the electronic ground state and is tuned through the local crystalline electric field. This is notably the case in the ${\mathrm{CeCo}}_x{\mathrm{Rh}}_{1-x}{\mathrm{In}}_5$ system where the ground-state wave function can provide the basis for antiferromagnetism and/or unconventional superconductivity. We develop a methodology to understand the local magnetic anisotropy and experimentally investigate with neutron spectroscopy applied to antiferromagnetic ( $T_N=3.8\mathrm{K}$ ) ${\mathrm{CeRhIn}}_5$ , which is isostructural to $d$ -wave superconducting ( $T_c=2.3\mathrm{K}$ ) ${\mathrm{CeCoIn}}_5$ . Through diagonalizing the local crystal field Hamiltonian with discrete tetragonal $C_4$ point group symmetry and coupling these states with the random phase approximation, we find two distinct modes polarized along the crystallographic $c$ and $a-b$ planes, agreeing with experiment. The anisotropy and bandwidth, underlying the energy scale of these modes, are tuneable with a magnetic field which we use experimentally to separate in energy single and multiparticle excitations thereby demonstrating the instability of excitations polarized within the crystallographic $a-b$ plane in ${\mathrm{CeRhIn}}_5$ . We compare this approach to a $S_{\mathrm{eff}}=\frac{1}{2}$ parametrizations and argue for the need to extend conventional SU(2) theories of magnetic excitations to utilize the multilevel nature of the underlying crystal-field basis states constrained by the local point-group $C_4$ symmetry. Published by the American Physical Society 2024

• Sponsoring Organization: USDOE
• OSTI ID: 2438389
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 6 Vol. 110; ISSN 2469-9950; ISSN PRBMDO
• Publisher: American Physical SocietyCopyright Statement
• Country of Publication: United States
• Language: English