Competing spin-orbital singlet states in the 4d4 honeycomb ruthenate Ag3LiRu2O6
Abstract
When spin-orbit-entangled d electrons reside on a honeycomb lattice, rich quantum states are anticipated to emerge, as exemplified by the d5 Kitaev materials. Distinct yet equally intriguing physics may be realized with a d-electron count other than d5. The magnetization, 7Li-nuclear magnetic resonance (NMR), and inelastic neutron scattering measurements, together with the quantum chemistry calculation, indicate that the layered ruthenate Ag3LiRu2O6 with d4Ru4+ ions at ambient pressure forms a honeycomb lattice of spin-orbit-entangled singlets, which is a playground for frustrated excitonic magnetism. Under pressure, the singlet state does not develop the expected excitonic magnetism, but two successive transitions to other nonmagnetic phases were found in 7Li-NMR, neutron diffraction, and x-ray absorption fine structure measurements, first to an intermediate phase with moderate distortion of honeycomb lattice and eventually to a high-pressure phase with very short Ru-Ru dimer bonds. While the strong dimerization in the high-pressure phase originates from a molecular orbital formation as in the sister compound Li2RuO3, we argue that the intermediate phase represents a spin-orbit-coupled singlet dimer state which is stabilized by the admixture of upper-lying Jeff=1-derived states via a pseudo-Jahn-Teller effect. The emergence of competing electronic phases demonstrates rich spin-orbital physics of d4 honeycomb compounds, and this finding paves the way for realization of unconventional magnetism.
Citation
Takayama , T , Blankenhorn , M , Bertinshaw , J , Haskel , D , Bogdanov , N A , Kitagawa , K , Yaresko , A N , Krajewska , A , Bette , S , McNally , G , Gibbs , A S , Matsumoto , Y , Sari , D P , Watanabe , I , Fabbris , G , Bi , W , Larkin , T I , Rabinovich , K S , Boris , A V , Ishii , H , Yamaoka , H , Irifune , T , Bewley , R , Ridley , C J , Bull , C L , Dinnebier , R , Keimer , B & Takagi , H 2022 , ' Competing spin-orbital singlet states in the 4d 4 honeycomb ruthenate Ag 3 LiRu 2 O 6 ' , Physical Review Research , vol. 4 , no. 4 , 043079 . https://doi.org/10.1103/PhysRevResearch.4.043079
Publication
Physical Review Research
Status
Peer reviewed
ISSN
2643-1564Type
Journal article
Description
Funding: The authors acknowledge the provision of beamtimes on PEARL (Proposal No. RB1920241 ) and MAPS (Proposal No. RB1820520) to Science & Technology Facilities Council (STFC). They thank the RIKEN-RAL muon facilities for the allocation of beamtime on ARGUS at ISIS Neutron and Muon Source (Proposal No. RB1970001). They thank the National Synchrotron Radiation Research Center and the Japan Synchrotron Radiation Research Institute for the allocation of beamtime for high-pressure x-ray diffraction measurements at BL12B2 of SPring-8 (Proposal No. 2018B4139). Work at Argonne is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC- 02-06CH11357. W.B. acknowledges partial support by the Consortium for Materials Properties Research in Earth Sciences. This paper is partly supported by the Alexander von Humboldt Foundation.Collections
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