Fermionic response from fractionalization in an insulating two-dimensional magnet

By J. Nasu, J. Knolle, D. Kovrizhin, Yukitoshi Motome, Roderich Moessner. Nature Physics, 2016

250 citations recorded by the source corpus.

An intriguing state of matter known as a quantum spin liquid has been predicted to host Majorana fermions. A detailed theoretical and numerical analysis re-interprets existing Raman data for α-RuCl3 and uncovers direct evidence of a fermionic response. Conventionally ordered magnets possess bosonic elementary excitations, called magnons. By contrast, no magnetic insulators in more than one dimension are known whose excitations are not bosons but fermions. Theoretically, some quantum spin liquids (QSLs)1—new topological phases that can occur when quantum fluctuations preclude an ordered state—are known to exhibit Majorana fermions2 as quasiparticles arising from fractionalization of spins3. Alas, despite much searching, their experimental observation remains elusive. Here, we show that fermionic excitations are remarkably directly evident in experimental Raman scattering data4 across a broad energy and temperature range in the two-dimensional material α-RuCl3. This shows the importance of magnetic materials as hosts of Majorana fermions. In turn, this first systematic evaluation of the dynamics of a QSL at finite temperature emphasizes the role of excited states for detecting such exotic properties associated with otherwise hard-to-identify topological QSLs.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/09a216651bc5b038b513e7a46f94fa9fdc728240

How researchers see this paper

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

In Atomic and Molecular Physics, and Optics

1. Simon Trebst
2. C. Hickey
3. J. Knolle
4. Roderich Moessner
5. Arnab Banerjee

In Condensed Matter Physics

1. Simon Trebst
2. C. Hickey
3. J. Knolle
4. S. Nagler
5. Roderich Moessner

In Electrical and Electronic Engineering

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

Citations in the corpus

• Kitaev materials (2017, methodology): “This includes the first experimental evidence of fermionic excitations in Raman scattering of a magnetic insulator [135, 136] and a number of highly unusual signatures in inelastic neutron scattering (above the magnetic ordering transition) that can be well attributed to the proximity of spin liquid”
• Excitations in the field-induced quantum spin liquid state of α-RuCl3 (2017, background): “The overall features of the inelastic neutron scattering (INS) response resemble those of the Kitaev QSL [15-17] and are consistent with an unusual response seen in Raman scattering [16, 18, 19], suggesting that the system is proximate to a QSL state exhibiting magnetic Majorana fermion excitations ”