TY - JOUR
T1 - Phonon dynamics in the Kitaev spin liquid
AU - Ye, Mengxing
AU - Fernandes, Rafael M.
AU - Perkins, Natalia B.
N1 - Publisher Copyright:
© 2020 authors. Published by the American Physical Society.
PY - 2020/8
Y1 - 2020/8
N2 - The search for fractionalization in quantum spin liquids largely relies on their decoupling with the environment. However, the spin-lattice interaction is inevitable in a real setting. While the Majorana fermion evades a strong decay due to the gradient form of spin-lattice coupling, the study of the phonon dynamics may serve as an indirect probe of fractionalization of spin degrees of freedom. Here we propose that the signatures of fractionalization can be seen in the sound attenuation and the Hall viscosity. Despite the fact that both quantities can be related to the imaginary part of the phonon self-energy, their origins are quite different, and the time-reversal symmetry breaking is required for the Hall viscosity. First, we compute the sound attenuation due to a phonon decay by scattering with a pair of Majorana fermions and show that it is linear in temperature (∼T). We argue that it has a particular angular dependence providing the information about the spin-lattice coupling and the low-energy Majorana-fermion spectrum. The observable effects in the absence of time-reversal symmetry are then analyzed. We obtain the phonon Hall viscosity term from the microscopic Hamiltonian with time-reversal symmetry-breaking term. Importantly, the Hall viscosity term mixes the longitudinal and transverse phonon modes and renormalizes the spectrum in a unique way, which may be probed in spectroscopy measurement.
AB - The search for fractionalization in quantum spin liquids largely relies on their decoupling with the environment. However, the spin-lattice interaction is inevitable in a real setting. While the Majorana fermion evades a strong decay due to the gradient form of spin-lattice coupling, the study of the phonon dynamics may serve as an indirect probe of fractionalization of spin degrees of freedom. Here we propose that the signatures of fractionalization can be seen in the sound attenuation and the Hall viscosity. Despite the fact that both quantities can be related to the imaginary part of the phonon self-energy, their origins are quite different, and the time-reversal symmetry breaking is required for the Hall viscosity. First, we compute the sound attenuation due to a phonon decay by scattering with a pair of Majorana fermions and show that it is linear in temperature (∼T). We argue that it has a particular angular dependence providing the information about the spin-lattice coupling and the low-energy Majorana-fermion spectrum. The observable effects in the absence of time-reversal symmetry are then analyzed. We obtain the phonon Hall viscosity term from the microscopic Hamiltonian with time-reversal symmetry-breaking term. Importantly, the Hall viscosity term mixes the longitudinal and transverse phonon modes and renormalizes the spectrum in a unique way, which may be probed in spectroscopy measurement.
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U2 - 10.1103/PhysRevResearch.2.033180
DO - 10.1103/PhysRevResearch.2.033180
M3 - Article
AN - SCOPUS:85093863276
SN - 2643-1564
VL - 2
JO - Physical Review Research
JF - Physical Review Research
IS - 3
M1 - 033180
ER -