Signatures of coupling between spin waves and Dirac fermions in YbMnBi2

A. Sapkota; L. Classen; M. B. Stone; A. T. Savici; V. O. Garlea; Aifeng Wang; J. M. Tranquada; C. Petrovic; I. A. Zaliznyak

doi:10.1103/PhysRevB.101.041111

Signatures of coupling between spin waves and Dirac fermions in YbMnBi2

A. Sapkota, L. Classen, M. B. Stone, A. T. Savici, V. O. Garlea, Aifeng Wang, J. M. Tranquada, C. Petrovic, I. A. Zaliznyak

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Abstract

We present inelastic neutron scattering measurements of magnetic excitations in YbMnBi2, which reveal features consistent with a direct coupling of magnetic excitations to Dirac fermions. In contrast with the large broadening of magnetic spectra observed in antiferromagnetic metals such as the iron pnictides, here the spin waves exhibit a small but resolvable intrinsic width, consistent with our theoretical analysis. The subtle manifestation of spin-fermion coupling is a consequence of the Dirac nature of the conduction electrons, including the vanishing density of states near the Dirac points. Accounting for the Dirac fermion dispersion specific to YbMnBi2 leads to particular signatures, such as the nearly wave-vector-independent damping observed in the experiment.

Original language	English
Article number	041111
Journal	Physical Review B
Volume	101
Issue number	4
DOIs	https://doi.org/10.1103/PhysRevB.101.041111
State	Published - Jan 24 2020

Funding

We thank Alexei Tsvelik and Michael Scherer for helpful comments and discussions. The work at Brookhaven National Laboratory was supported by the Office of Basic Energy Sciences, Materials Sciences and Engineering Division, U.S. Department of Energy (DOE) under Contract No. DE-SC0012704. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. L.C. acknowledges funding from a Feodor-Lynen research fellowship of the Alexander von Humboldt Foundation.

Funders	Funder number
U.S. Department of Energy	DE-SC0012704
Alexander von Humboldt-Stiftung
Basic Energy Sciences
Division of Materials Sciences and Engineering

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abstract = "We present inelastic neutron scattering measurements of magnetic excitations in YbMnBi2, which reveal features consistent with a direct coupling of magnetic excitations to Dirac fermions. In contrast with the large broadening of magnetic spectra observed in antiferromagnetic metals such as the iron pnictides, here the spin waves exhibit a small but resolvable intrinsic width, consistent with our theoretical analysis. The subtle manifestation of spin-fermion coupling is a consequence of the Dirac nature of the conduction electrons, including the vanishing density of states near the Dirac points. Accounting for the Dirac fermion dispersion specific to YbMnBi2 leads to particular signatures, such as the nearly wave-vector-independent damping observed in the experiment.",

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AU - Sapkota, A.

AU - Classen, L.

AU - Stone, M. B.

AU - Savici, A. T.

AU - Garlea, V. O.

AU - Wang, Aifeng

AU - Tranquada, J. M.

AU - Petrovic, C.

AU - Zaliznyak, I. A.

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AB - We present inelastic neutron scattering measurements of magnetic excitations in YbMnBi2, which reveal features consistent with a direct coupling of magnetic excitations to Dirac fermions. In contrast with the large broadening of magnetic spectra observed in antiferromagnetic metals such as the iron pnictides, here the spin waves exhibit a small but resolvable intrinsic width, consistent with our theoretical analysis. The subtle manifestation of spin-fermion coupling is a consequence of the Dirac nature of the conduction electrons, including the vanishing density of states near the Dirac points. Accounting for the Dirac fermion dispersion specific to YbMnBi2 leads to particular signatures, such as the nearly wave-vector-independent damping observed in the experiment.

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Signatures of coupling between spin waves and Dirac fermions in YbMnBi2

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