Spin-Orbit-Lattice Entangled State in A2MgReO6 (A = Ca, Sr, Ba) Revealed by Resonant Inelastic X-Ray Scattering

Authors

Abstract

The 5d1 ordered double perovskites present an exotic playground for studying novel multipolar physics due to large spin-orbit coupling. We present Re L3 edge resonant inelastic Xray scattering (RIXS) results that reveal the presence of the dynamic Jahn-Teller effect in theA2MgReO6 (A = Ca, Sr, Ba) family of 5d1 double perovskites. The spin-orbit excitations in these materials show a strongly asymmetric lineshape and exhibit substantial temperature dependence, indicating that they are dressed with lattice vibrations. Our experimental results are explained quantitatively through a RIXS calculation based on a spin-orbit-lattice entangled electronic ground state with the dynamic Jahn-Teller effect taken into consideration. We find that the spin-orbitlattice entangled state is robust against magnetic and structural phase transitions as well as against significant static Jahn-Teller distortions. Our results illustrate the importance of including vibroniccoupling for a complete description of the ground state physics of 5d1 double perovskites.