Spin-orbit coupling in a half-filled $t_{2g}$ shell: the case of $5d^3$ K${}_2$ReCl${}_6$

Abstract

The half-filled $t_{2g}$ shell of the $t_{2g}^3$ configuration usually, in LS coupling, hosts a S = 3/2 ground state with quenched orbital moment. This state is not Jahn-Teller active. Sufficiently large spin-orbit coupling $\zeta$ has been predicted to change this picture by mixing in orbital moment, giving rise to a sizable Jahn-Teller distortion. In $5d^3$ K${}_2$ReCl${}_6$ we study the electronic excitations using resonant inelastic x-ray scattering (RIXS) and optical spectroscopy. We observe on-site intra-$t_{2g}$ excitations below 2 eV and corresponding overtones with two intra-$t_{2g}$ excitations on adjacent sites, the Mott gap at 2.7 eV, $t_{2g}$-to-$e_g$ excitations above 3 eV, and charge-transfer excitations at still higher energy. The intra-$t_{2g}$ excitation energies are a sensitive measure of $\zeta$ and Hund's coupling $J_H$. The sizable value of $\zeta \approx$ 0.29 eV places K${}_2$ReCl${}_6$ into the intermediate coupling regime, but $\zeta /J_H\approx 0.6$ is not sufficiently large to drive a pronounced Jahn-Teller effect. We discuss the ground state wavefunction in a Kanamori picture and find that the S = 3/2 multiplet still carries about 97 % of the weight. However, the finite admixture of orbital moment allows for subtle effects. We discuss small temperature-induced changes of the optical data and find evidence for a lowering of the ground state by about 3 meV below the structural phase transitions.

16 pages, 14 figures

References in corpus (20)

• Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models
• Strong electronic correlations from Hund's coupling
• Models and Materials for Generalized Kitaev Magnetism
• Spin-orbit-entangled electronic phases in 4$d$ and 5$d$ transition-metal compounds
• The frustrated FCC antiferromagnet Ba2YOsO6: structural characterization, magnetic properties and neutron scattering studies
• The Jahn-Teller effect and spin--orbit coupling: friends or foes?
• Ferro-octupolar order and low-energy excitations in d${}^2$ double perovskites of Osmium
• Exchange interactions, Jahn-Teller coupling, and multipole orders in pseudospin one-half $5{\mathbf{d}}^2$ Mott insulators
• Cubic symmetry and magnetic frustration on the $fcc$ spin lattice in K${}_2$IrCl${}_6$
• Nonmagnetic $J=0$ State and Spin-Orbit Excitations in K${}_2$RuCl${}_6$
• Octupolar order and Ising quantum criticality tuned by strain and dimensionality: Application to $d$-orbital Mott insulators
• Interplay of spin-orbit coupling and hybridization in Ca3LiOsO6 and Ca3LiRuO6
• Lone octupole and bulk magnetism in osmate 5d2 double perovskites
• Field-induced Kitaev multipolar liquid in spin-orbit coupled $d^2$ honeycomb Mott insulators
• Interplay of magnetic order and ferroelasticity in the spin-orbit coupled antiferromagnet K${}_2$ReCl${}_6$
• Electronic excitations in $5d^4$ J=0 Os${}^{4+}$ halides studied by RIXS and optical spectroscopy
• Local symmetry breaking and low-energy continuum in K${}_2$ReCl${}_6$
• Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^4$ magnet
• Spin-orbit coupling and crystal-field splitting in Ti-doped Ca2RuO4 studied by ellipsometry
• Low-energy electronic interactions in ferrimagnetic Sr2CrReO6 thin films

Cited by in corpus (5)

• Dynamic Jahn-Teller Phenomena in Heavy Transition Metal Compounds
• Spin-orbital-lattice entanglement in the ideal j=1/2 compound K${}_2$IrCl${}_6$
• Resonant inelastic X-ray scattering investigation of Hund's and spin-orbit coupling in $5d^2$ double perovskites
• Quasimolecular electronic structure of the trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$
• Structural studies on $A_2$ReCl${}_6$ ($A$=K, Rb, Cs): absence of Jahn-Teller distortion