Direct evidence for dominant bond-directional interactions in a honeycomb lattice iridate Na2IrO3

By S. Chun, Jong-Woo Kim, Jungho Kim, Hong Zheng, C. Stoumpos, C. Malliakas, J. Mitchell, K. Mehlawat, Y. Singh, Yongseong Choi and 8 more. Nature Physics, 2015

353 citations recorded by the source corpus.

Honeycomb iridates have been proposed as experimental realizations of the Kitaev model. An X-ray scattering study presents evidence for bond-directional interactions in Na2IrO3, a key requirement to make the connection with Kitaev physics possible. Heisenberg interactions are ubiquitous in magnetic materials and play a central role in modelling and designing quantum magnets. Bond-directional interactions1,2,3 offer a novel alternative to Heisenberg exchange and provide the building blocks of the Kitaev model4, which has a quantum spin liquid as its exact ground state. Honeycomb iridates, A2IrO3 (A = Na, Li), offer potential realizations of the Kitaev magnetic exchange coupling, and their reported magnetic behaviour may be interpreted within the Kitaev framework. However, the extent of their relevance to the Kitaev model remains unclear, as evidence for bond-directional interactions has so far been indirect. Here we present direct evidence for dominant bond-directional interactions in antiferromagnetic Na2IrO3 and show that they lead to strong magnetic frustration. Diffuse magnetic X-ray scattering reveals broken spin-rotational symmetry even above the Néel temperature, with the three spin components exhibiting short-range correlations along distinct crystallographic directions. This spin- and real-space entanglement directly uncovers the bond-directional nature of these interactions, thus providing a direct connection between honeycomb iridates and Kitaev physics.

Subfields: Condensed Matter Physics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/1e486bbfc07cefdfbc7183688930cf93c8e7f4e4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Condensed Matter Physics

1. Simon Trebst
2. C. Hickey
3. J. Knolle
4. Roderich Moessner
5. T. Senthil
6. I. Kimchi
7. R. Cava
8. S. Nagler

In Electrical and Electronic Engineering

1. Simon Trebst
2. C. Hickey
3. D. Mandrus

Citations in the corpus

• Physics of the Kitaev Model: Fractionalization, Dynamic Correlations, and Material Connections (2017, background): “In Na2IrO3, an unusual relation between spin and momentum at temperatures above the zigzag ordering transition provides direct evidence for strong Kitaev exchange [27].”
• Excitations in the field-induced quantum spin liquid state of α-RuCl3 (2017, background): “In all the systems studied to date significant non-Kitaev interactions induce magnetic order at low temperature.(3,17,18) However, in-plane magnetic fields of roughly 8 T suppress the long-range magnetic order in α-RuCl3, 3–10 raising the intriguing possibility of a fieldinduced quantum spin liquid ”
• Quantum spin liquids (2019, background): “2D) indeed occur in this class of materials (108).”
• Kitaev materials (2017, background): “Not only have several Kitaev materials with different two- and three-dimensional lattice geometries been synthesized and firmly established as j = 1/2 spin-orbit entangled Mott insulators, but there has also been a streak of impressive experimental findings that most notably have provided direct evi”