Title: Giant phonon anomalies in the proximate Kitaev quantum spin liquid α-RuCl₃

Abstract

The Kitaev quantum spin liquid epitomizes an entangled topological state, for which two flavors of fractionalized low-energy excitations are predicted: the itinerant Majorana fermion and the Z2 gauge flux. It was proposed recently that fingerprints of fractional excitations are encoded in the phonon spectra of Kitaev quantum spin liquids through a novel fractional-excitation-phonon coupling. Here, we detect anomalous phonon effects in α-RuCl3 using inelastic X-ray scattering with meV resolution. At high temperature, we discover interlaced optical phonons intercepting a transverse acoustic phonon between 3 and 7 meV. Upon decreasing temperature, the optical phonons display a large intensity enhancement near the Kitaev energy, JK~8 meV, that coincides with a giant acoustic phonon softening near the Z2 gauge flux energy scale. These phonon anomalies signify the coupling of phonon and Kitaev magnetic excitations in α-RuCl3 and demonstrates a proof-of-principle method to detect anomalous excitations in topological quantum materials.

Authors:

Li, Haoxiang ^[1]; Zhang, Tiantian ^[2]; Said, A. H. ^[3]; Fabbris, Gilberto  ^[3];

• Search DOE PAGES for author "Fabbris, Gilberto"
• Search DOE PAGES for ORCID "0000-0001-8278-4985"

Mazzone, Daniel G.  ^[4];

• Search DOE PAGES for author "Mazzone, Daniel G."
• Search DOE PAGES for ORCID "0000-0002-0421-0625"

Yan, Jiaqiang ^[1]; Mandrus, David ^[5]; Halász, Gábor B. ^[1]; Okamoto, Satoshi  ^[1];

• Search DOE PAGES for author "Okamoto, Satoshi"
• Search DOE PAGES for ORCID "0000-0002-0493-7568"

Murakami, S.  ^[2];

• Search DOE PAGES for author "Murakami, S."
• Search DOE PAGES for ORCID "0000-0002-2033-9402"

Dean, M. P. M.  ^[6];

• Search DOE PAGES for author "Dean, M. P. M."
• Search DOE PAGES for ORCID "0000-0001-5139-3543"

Lee, Ho Nyung  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-2180-3975"

Miao, Hu  ^[1]

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• Search DOE PAGES for ORCID "0000-0003-1078-5713"

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Tokyo Institute of Technology (Japan)
3. Argonne National Lab. (ANL), Argonne, IL (United States)
4. Brookhaven National Lab. (BNL), Upton, NY (United States); Paul Scherrer Inst. (PSI), Villigen (Switzerland)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
6. Brookhaven National Lab. (BNL), Upton, NY (United States)

Publication Date:

Thu Jun 10 00:00:00 EDT 2021

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; Gordon and Betty Moore Foundation; Japan Society for the Promotion of Science (JSPS)

OSTI Identifier:

1787494

Alternate Identifier(s):

OSTI ID: 1782548; OSTI ID: 1805025

Report Number(s):

BNL-221379-2021-JAAM
Journal ID: ISSN 2041-1723; 161217

Grant/Contract Number:  

AC02-06CH11357; SC0012704; 21K13865; JP18H03678; GBMF9069; AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Nature Communications

Additional Journal Information:

Journal Volume: 12; Journal Issue: 1; Journal ID: ISSN 2041-1723

Publisher:

Nature Publishing Group

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Inelastic x-ray scattering; Kitaev quantum spin liquid; RuCl₃; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Magnetic properties and materials; Quantum fluids and solids