title: Raman spectroscopic signature of fractionalized excitations in the harmonic-honeycomb iridates β- and γ-Li2IrO3.
abstract: The fractionalization of elementary excitations in quantum spin systems is a central theme in current condensed matter physics. The Kitaev honeycomb spin model provides a prominent example of exotic fractionalized quasiparticles, composed of itinerant Majorana fermions and gapped gauge fluxes. However, identification of the Majorana fermions in a three-dimensional honeycomb lattice remains elusive. Here we report spectroscopic signatures of fractional excitations in the harmonic-honeycomb iridates β- and γ-Li2IrO3. Using polarization-resolved Raman spectroscopy, we find that the dynamical Raman response of β- and γ-Li2IrO3 features a broad scattering continuum with distinct polarization and composition dependence. The temperature dependence of the Raman spectral weight is dominated by the thermal damping of fermionic excitations. These results suggest the emergence of Majorana fermions from spin fractionalization in a three-dimensional Kitaev-Heisenberg system.
authors.affiliation: Department of Physics, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul 156-756, Republic of Korea.
authors.forename: A
authors.initials: A
authors.lastname: Glamazda
authors.affiliation: Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany.|Laboratory for Emerging Nanometrology (LENA), TU Braunschweig, D-38106 Braunschweig, Germany.
authors.forename: P
authors.identifier: 0000-0002-0894-3412
authors.initials: P
authors.lastname: Lemmens
authors.affiliation: Department of Physics, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul 156-756, Republic of Korea.
authors.forename: S-H
authors.initials: SH
authors.lastname: Do
authors.affiliation: Department of Physics, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul 156-756, Republic of Korea.
authors.forename: Y S
authors.initials: YS
authors.lastname: Choi
authors.affiliation: Department of Physics, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul 156-756, Republic of Korea.
authors.forename: K-Y
authors.initials: KY
authors.lastname: Choi