title: Giant suppression of phononic heat transport in a quantum magnet BiCu2PO6.
abstract: Thermal transport of quantum magnets has elucidated the nature of low energy elementary excitations and complex interplay between those excited states via strong scattering of thermal carriers. BiCu2PO6is a unique frustrated spin-ladder compound exhibiting highly anisotropic spin excitations that contain both itinerant and localized dispersion characters along the b- and a-axes respectively. Here, we investigate thermal conductivity κ of BiCu2PO6under high magnetic fields (H) of up to 30 tesla. A dip-feature in κ, located at ~15 K at zero-H along all crystallographic directions, moves gradually toward lower temperature (T) with increasing H, thus resulting in giant suppression by a factor of ~30 near the critical magnetic field of Hc≅ 23.5 tesla. The giant H- and T-dependent suppression of κ can be explained by the combined result of resonant scattering of phononic heat carriers with magnetic energy levels and increased phonon scattering due to enhanced spin fluctuation at Hc, unequivocally revealing the existence of strong spin-phonon coupling. Moreover, we find an experimental indication that the remaining magnetic heat transport along the b-axis becomes almost gapless at the magnetic quantum critical point realized at Hc.
authors.affiliation: CeNSCMR, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: Byung-Gu
authors.initials: BG
authors.lastname: Jeon
authors.affiliation: CeNSCMR, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: B
authors.initials: B
authors.lastname: Koteswararao
authors.affiliation: CeNSCMR, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: C B
authors.initials: CB
authors.lastname: Park
authors.affiliation: Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: G J
authors.initials: GJ
authors.lastname: Shu
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Riggs
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
authors.forename: E G
authors.initials: EG
authors.lastname: Moon
authors.affiliation: Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea.|Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
authors.forename: S B
authors.initials: SB
authors.lastname: Chung
authors.affiliation: Center of Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: F C
authors.initials: FC
authors.lastname: Chou
authors.affiliation: CeNSCMR, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.|Institute of Applied Physics, Seoul National University, Seoul 151-747, Korea.
authors.forename: Kee Hoon
authors.initials: KH
authors.lastname: Kim