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Title: Weak coupling of pseudoacoustic phonons and magnon dynamics in the incommensurate spin-ladder compound S r 14 C u 24 O 41

Abstract

Intriguing lattice dynamics have been predicted for aperiodic crystals that contain incommensurate substructures. Here we report inelastic neutron scattering measurements of phonon and magnon dispersions in Sr 14Cu 24O 41, which contains incommensurate one-dimensional (1D) chain and two-dimensional (2D) ladder substructures. Two distinct pseudoacoustic phonon modes, corresponding to the sliding motion of one sublattice against the other, are observed for atomic motions polarized along the incommensurate axis. In the long wavelength limit, it is found that the sliding mode shows a remarkably small energy gap of 1.7–1.9 meV, indicating very weak interactions between the two incommensurate sublattices. The measurements also reveal a gapped and steep linear magnon dispersion of the ladder sublattice. The high group velocity of this magnon branch and weak coupling with acoustic and pseudoacoustic phonons can explain the large magnon thermal conductivity in Sr 14Cu 24O 41 crystals. In addition, the magnon specific heat is determined from the measured total specific heat and phonon density of states and exhibits a Schottky anomaly due to gapped magnon modes of the spin chains. Furthermore, these findings offer new insights into the phonon and magnon dynamics and thermal transport properties of incommensurate magnetic crystals that contain low-dimensional substructures.

Authors:
 [1];  [2];  [1];  [2];  [2];  [1];  [3];  [1]
  1. The Univ. of Texas at Austin, Austin, TX (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Duke Univ., Durham, NC (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1337851
Alternate Identifier(s):
OSTI ID: 1329503
Grant/Contract Number:  
AC05-00OR22725; SC0016166
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 13; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Chen, Xi, Bansal, Dipanshu, Sullivan, Sean, Abernathy, Douglas L., Aczel, Adam A., Zhou, Jianshi, Delaire, Olivier A., and Shi, Li. Weak coupling of pseudoacoustic phonons and magnon dynamics in the incommensurate spin-ladder compound Sr14Cu24O41. United States: N. p., 2016. Web. doi:10.1103/PhysRevB.94.134309.
Chen, Xi, Bansal, Dipanshu, Sullivan, Sean, Abernathy, Douglas L., Aczel, Adam A., Zhou, Jianshi, Delaire, Olivier A., & Shi, Li. Weak coupling of pseudoacoustic phonons and magnon dynamics in the incommensurate spin-ladder compound Sr14Cu24O41. United States. doi:10.1103/PhysRevB.94.134309.
Chen, Xi, Bansal, Dipanshu, Sullivan, Sean, Abernathy, Douglas L., Aczel, Adam A., Zhou, Jianshi, Delaire, Olivier A., and Shi, Li. Fri . "Weak coupling of pseudoacoustic phonons and magnon dynamics in the incommensurate spin-ladder compound Sr14Cu24O41". United States. doi:10.1103/PhysRevB.94.134309. https://www.osti.gov/servlets/purl/1337851.
@article{osti_1337851,
title = {Weak coupling of pseudoacoustic phonons and magnon dynamics in the incommensurate spin-ladder compound Sr14Cu24O41},
author = {Chen, Xi and Bansal, Dipanshu and Sullivan, Sean and Abernathy, Douglas L. and Aczel, Adam A. and Zhou, Jianshi and Delaire, Olivier A. and Shi, Li},
abstractNote = {Intriguing lattice dynamics have been predicted for aperiodic crystals that contain incommensurate substructures. Here we report inelastic neutron scattering measurements of phonon and magnon dispersions in Sr14Cu24O41, which contains incommensurate one-dimensional (1D) chain and two-dimensional (2D) ladder substructures. Two distinct pseudoacoustic phonon modes, corresponding to the sliding motion of one sublattice against the other, are observed for atomic motions polarized along the incommensurate axis. In the long wavelength limit, it is found that the sliding mode shows a remarkably small energy gap of 1.7–1.9 meV, indicating very weak interactions between the two incommensurate sublattices. The measurements also reveal a gapped and steep linear magnon dispersion of the ladder sublattice. The high group velocity of this magnon branch and weak coupling with acoustic and pseudoacoustic phonons can explain the large magnon thermal conductivity in Sr14Cu24O41 crystals. In addition, the magnon specific heat is determined from the measured total specific heat and phonon density of states and exhibits a Schottky anomaly due to gapped magnon modes of the spin chains. Furthermore, these findings offer new insights into the phonon and magnon dynamics and thermal transport properties of incommensurate magnetic crystals that contain low-dimensional substructures.},
doi = {10.1103/PhysRevB.94.134309},
journal = {Physical Review B},
number = 13,
volume = 94,
place = {United States},
year = {Fri Oct 21 00:00:00 EDT 2016},
month = {Fri Oct 21 00:00:00 EDT 2016}
}

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Works referenced in this record:

Quasicrystals: A New Class of Ordered Structures
journal, December 1984


Van der Waals heterostructures
journal, July 2013

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