Abstract
The Kitaev quantum spin liquid (KSL) is a theoretically predicted state of matter whose fractionalized quasiparticles are distinct from bosonic magnons, the fundamental excitation in ordered magnets. The layered honeycomb antiferromagnet α-RuCl3 is a KSL candidate material, as it can be driven to a magnetically disordered phase by application of an in-plane magnetic field, with Hc∼7T. Here, we report a detailed characterization of the magnetic excitation spectrum of this material by high-resolution time-domain terahertz spectroscopy. We observe two sharp magnon resonances whose frequencies and amplitudes exhibit a discontinuity as a function of applied magnetic field, as well as two broader peaks at higher energy. Below the Néel temperature, we find that linear spin wave theory can account for all of these essential features of the spectra when a C3-breaking distortion of the honeycomb lattice and the presence of structural domains are taken into account.
| Original language | English |
|---|---|
| Article number | 094425 |
| Journal | Physical Review B |
| Volume | 98 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 26 2018 |
Funding
Terahertz spectroscopy was performed at Lawrence Berkeley National Laboratory under the Spin Physics program (KC2206) supported by the U. S. DOE, Office of Science, Office of Basic Energy Science, Materials Sciences and Engineering Division under Contract No. DE-AC02-05-CH11231. Laue microdiffraction measurements were carried out at beam line 12.3.2 at the Advanced Light Source, which is a Department of Energy User Facility under Contract No. DE-AC02-05CH11231. Device fabrication and dc conductivity measurement were done at Stanford University under the Spin Physics program supported by the US DOE, Office of Science, Office of Basic Energy Science, Materials Sciences and Engineering Division under Contract No. DE-AC02-76SF00515. A.L. and L.W. were supported by the Gordon and Betty Moore Foundation's EPiQs Initiative through the Grant No. GBMF4537 to J.O. at U. C. Berkeley. The work at ORNL was supported by the U. S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (J.Q.Y. and C.B.), and Division of Scientific User Facilities (A.B. and S.E.N.) under Contract No. DE-AC05-00OR22725. P.L.K. and D.M. acknowledge financial support from Gordon and Betty Moore Foundation's EPiQS Initiative through Grant No. GBMF44. E.A. acknowledges financial support from the ERC synergy grant UQUAM. D.B.'s participation in this research was facilitated in part by a National Physical Science Consortium Fellowship and by stipend support from the National Institute of Standards and Technology. We thank N. Tamura and C. V. Stan for support at the Advanced Light Source and E. Angelino for help processing the Laue microdiffraction data. We thank T. Scaffidi for useful discussions. Terahertz spectroscopy was performed at Lawrence Berkeley National Laboratory under the Spin Physics program (KC2206) supported by the U. S. DOE, Office of Science, Office of Basic Energy Science, Materials Sciences and Engineering Division under Contract No. DE-AC02-05-CH11231. Laue microdiffraction measurements were carried out at beam line 12.3.2 at the Advanced Light Source, which is a Department of Energy User Facility under Contract No. DE-AC02-05CH11231. Device fabrication and dc conductivity measurement were done at Stanford University under the Spin Physics program supported by the US DOE, Office of Science, Office of Basic Energy Science, Materials Sciences and Engineering Division under Contract No. DE-AC02-76SF00515. A.L. and L.W. were supported by the Gordon and Betty Moore Foundation's EPiQs Initiative through the Grant No. GBMF4537 to J.O. at U. C. Berkeley. The work at ORNL was supported by the U. S. DOE, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (J.Q.Y. and C.B.), and Division of Scientific User Facilities (A.B. and S.E.N.) under Contract No. DE-AC05-00OR22725. P.L.K. and D.M. acknowledge financial support from Gordon and Betty Moore Foundation's EPiQS Initiative through Grant No. GBMF44. E.A. acknowledges financial support from the ERC synergy grant UQUAM. D.B.'s participation in this research was facilitated in part by a National Physical Science Consortium Fellowship and by stipend support from the National Institute of Standards and Technology. L.W., A.L., and E.E.A contributed equally to this work. APPENDIX A: