title: Twisting phonons in complex crystals with quasi-one-dimensional substructures.
abstract: A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such complex crystals. Here we employ inelastic neutron scatting measurements and density functional theory calculations to show that numerous low-energy optical vibrational modes exist in higher manganese silicides, an example of such crystals. These optical modes, including unusually low-frequency twisting motions of the Si ladders inside the Mn chimneys, provide a large phase space for scattering acoustic phonons. A hybrid phonon and diffuson model is proposed to explain the low and anisotropic thermal conductivity of higher manganese silicides and to evaluate nanostructuring as an approach to further suppress the thermal conductivity and enhance the thermoelectric energy conversion efficiency. This discovery offers new insights into the structure-property relationships of a broad class of materials with quasi-one-dimensional substructures for various applications.
authors: Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA.
authors: Xi
authors: X
authors: Chen
authors: Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
authors: Annie
authors: A
authors: Weathers
authors: Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les Nanomatériaux, Commissariat à l'Énergie Atomique Grenoble, Grenoble 38054, France.
authors: Jesús
authors: J
authors: Carrete
authors: Cornell Nanoscale Facility, Cornell University, Ithaca, New York 14853, USA.
authors: Saikat
authors: S
authors: Mukhopadhyay
authors: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Olivier
authors: O
authors: Delaire
authors: Cornell Nanoscale Facility, Cornell University, Ithaca, New York 14853, USA.
authors: Derek A
authors: DA
authors: Stewart
authors: Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les Nanomatériaux, Commissariat à l'Énergie Atomique Grenoble, Grenoble 38054, France.
authors: Natalio
authors: N
authors: Mingo
authors: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors: Steven N
authors: SN
authors: Girard
authors: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Jie
authors: J
authors: Ma
authors: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Douglas L
authors: DL
authors: Abernathy
authors: 1] Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA [2] Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Jiaqiang
authors: J
authors: Yan
authors: Laboratoire d'Innovation pour les Technologies des Energies Nouvelles et les Nanomatériaux, Commissariat à l'Énergie Atomique Grenoble, Grenoble 38054, France.
authors: Raman
authors: R
authors: Sheshka
authors: Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
authors: Daniel P
authors: DP
authors: Sellan
authors: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors: Fei
authors: F
authors: Meng
authors: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors: Song
authors: S
authors: Jin
authors: Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA.
authors: Jianshi
authors: J
authors: Zhou
authors: 1] Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA [2] Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
authors: Li
authors: 0000000254016839
authors: L
authors: Shi