Spin excitations of a proximate Kitaev quantum spin liquid realized in Cu${}_2$IrO${}_3$

Abstract

Magnetic moments arranged at the corners of a honeycomb lattice are predicted to form a novel state of matter, Kitaev quantum spin liquid, under the influence of frustration effects between bond-dependent Ising interactions. Some layered honeycomb iridates and related materials, such as Na${}_2$IrO${}_3$ and $\alpha$-RuCl${}_3$, are proximate to Kitaev quantum spin liquid, but bosonic spin-wave excitations associated with undesirable antiferromagnetic long-range order mask the inherent properties of Kitaev Hamiltonian. Here, we use ${}^{63}$Cu nuclear quadrupole resonance to uncover the low energy spin excitations in the nearly ideal honeycomb lattice of effective spin $S=1/2$ at the Ir${}^{4+}$ sites in Cu${}_2$IrO${}_3$. We demonstrate that, unlike Na${}_2$IrO${}_3$, Ir spin fluctuations exhibit no evidence for critical slowing down toward magnetic long range order in zero external magnetic field. Moreover, the low energy spin excitation spectrum is dominated by a mode that has a large excitation gap comparable to the Ising interactions, a signature expected for Majorana fermions of Kitaev quantum spin liquid.

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• ${}^{139}$La NMR investigation of the interplay between the lattice, charge, and spin dynamics in charge ordered high $T_c$ cuprate La${}_{1.875}$Ba${}_{0.125}$CuO${}_4$
• Revealing the Phase Diagram of Kitaev Materials by Machine Learning: Cooperation and Competition between Spin Liquids
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• Distribution of the magnetic environment in charge ordered La${}_{1.885}$Sr${}_{0.115}$CuO${}_4$
• Probing signatures of fractionalization in candidate quantum spin liquid Cu2IrO3 via anomalous Raman scattering
• Complex pressure-temperature structural phase diagram of honeycomb iridate Cu${}_2$IrO${}_3$
• NMR Investigation on Honeycomb Iridate Ag${}_3$LiIr${}_2$O${}_6$
• Impurity-induced resonant spinon zero modes in Dirac quantum spin-liquids
• Field evolution of magnetic phases and spin dynamics in the honeycomb lattice magnet Na2Co2TeO6: 23Na NMR study
• Freezing of the Lattice in the Kagome Lattice Heisenberg Antiferromagnet Zn-barlowite ZnCu${}_3$(OD)${}_6$FBr
• Pressure tuning of structure, magnetic frustration and carrier conduction in Kitaev spin liquid candidate Cu${}_2$IrO${}_3$: X-ray, Raman, magnetic susceptibility, resistivity and first-principles analysis
• Tunable moire spinons in magnetically encapsulated twisted van der Waals quantum spin-liquids
• Controlling magnetic frustration in 1T-TaS${}_2$ via Coulomb engineered long-range interactions
• Exploration of trivial and non-trivial electronic phases and of collinear and non-collinear magnetic phases in low-spin d${}^5$ perovskites
• Long-range order in the XY model on the honeycomb lattice
• High-temperature magnetic anomaly via suppression of antisite disorder through synthesis route modification in a Kitaev candidate Cu${}_2$IrO${}_3$
• Slow spin dynamics and quantum tunneling of magnetization in the dipolar antiferromagnet DyScO${}_3$
• Revisiting the ${}^{63}$Cu NMR signature of charge order in La${}_{1.875}$Ba${}_{0.125}$CuO${}_4$
• Chirality-selective topological magnon phase transition induced by interplay of anisotropic exchange interactions in honeycomb ferromagnet
• Coupled spin-1/2 antiferromagnetic chain Cs${}_2$LiRuCl${}_6$ with partially disordered crystal lattice
• Vacancies in generic Kitaev spin liquids
• Anomalous Proximitized Transport in Metal/Quantum Magnet Heterostructure $\mathrm{B}{\mathrm{i}}_2\mathrm{I}{\mathrm{r}}_2{\mathrm{O}}_7/Y{\mathrm{b}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$
• Local probe investigation of the spin dynamics in the kagome and inter-layers of orthorhombic barlowite Cu${}_4$(OD)${}_6$FBr: ${}^{79}$Br and ${}^{63}$Cu NQR study