Observation of the orbital quantum dynamics in the spin-1/2 hexagonal antiferromagnet Ba3CuSb2O9

Abstract

We explore orbital dynamics in the spin liquid candidate Ba3CuSb2O9 using multi-frequency electron spin resonance. We prepared two high quality single crystals. The crystal with a slight copper deficiency shows a structural phase transition at around 200 K due to the cooperative Jahn-Teller effect, accompanied with orbital ordering. In contrast, the crystal with almost perfect stoichiometry shows no orbital ordering down to the lowest temperature of 1.5 K. Dramatic change in the g-factor anisotropy as a function of frequency and temperature demonstrates orbital quantum fluctuations at a nearly constant time scale of ~ 100 ps below 20 K, evidencing the emergence of an orbital liquid state in this quantum spin liquid compound.

15 pages,4 figures, including 9 pages supplemental material

References in corpus (7)

• Spin-orbital quantum liquid on the honeycomb lattice
• Absence of Jahn-Teller transition in the hexagonal Ba3CuSb2O9 single crystal
• Spin-orbital resonating valence bond liquid on a triangular lattice: Evidence from finite-cluster diagonalization
• Spin dynamics in the low-dimensional magnet TiOCl
• Exploring the spin-orbital ground state of Ba3CuSb2O9
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Cited by in corpus (10)

• Thermal Hall effect in a phonon-glass Ba${}_3$CuSb${}_2$O${}_9$
• Emergent $\mathrm{SU}(4)$ Symmetry in $\alpha$-ZrCl${}_3$ and Crystalline Spin-Orbital Liquids
• Randomness-induced quantum spin liquid behavior in the s=1/2 random J1-J2 Heisenberg antiferromagnet on the honeycomb lattice
• Low-Energy Excitations and Ground State Selection in Quantum Breathing Pyrochlore Antiferromagnet Ba${}_3$Yb${}_2$Zn${}_5$O${}_{11}$
• Gapless quantum spin liquid in the triangular system Sr${}_3$CuSb${}_2$O${}_9$
• $\mathrm{SU}(4)$-Symmetric Quantum Spin-Orbital Liquids on Various Lattices
• Spin-Orbital Entangled Liquid State in the Copper Oxide Ba${}_3$CuSb${}_2$O${}_9$
• High-field Magnetism of the Honeycomb-lattice Antiferromagnet Cu${}_2$(pymca)${}_3$(ClO${}_4$)
• Cu-Sb dumbbell arrangement in the spin-orbital liquid candidate Ba${}_3$CuSb${}_2$O${}_9$
• Spin-orbital liquid in Ba${}_3$CuSb${}_2$O${}_9$ stabilized by oxygen holes