Weak coupling of pseudoacoustic phonons and magnon dynamics in incommensurate spin ladder compound Sr14Cu24O41

Abstract

Intriguing lattice dynamics has 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. These findings offer new insights into the phonon and magnon dynamics and thermal transport properties of incommensurate magnetic crystals that contain low-dimensional substructures.

References in corpus (14)

• Van der Waals heterostructures
• Mantid - Data Analysis and Visualization Package for Neutron Scattering and $\mu SR$ Experiments
• Surprises on the Way from 1D to 2D Quantum Magnets: the Novel Ladder Materials
• Glass-like phonon scattering from a spontaneous nanostructure in AgSbTe2
• Magnon Heat Transport in (Sr,La)_14Cu_24O_41
• The Spin Dynamics of the Spin Ladder, Dimer Chain Material Sr14Cu24O41
• Spin Dynamics in the Magnetic Chains Arrays of Sr14Cu24O41: a Neutron Inelastic scattering Investigation
• Quasi-two-dimensional hole ordering and dimerized state in the CuO2-chain layers in Sr14Cu24O41
• Optical Properties of the Spin-Ladder Compound Sr_{14}Cu_{24}O_{41}
• Magnetic excitations and structural change in the S=1/2 quasi-one-dimensional magnet Sr_{14-x}Y_{x}Cu_{24}O_{41} (0<x<1)
• Phononic gaps in the charged incommensurate planes of Sr14Cu24O41
• Spin gap evolution upon Ca doping in the spin ladder series $S{r}_{14-x}C{a}_{x}C{u}_{24}{O}_{41}$ by inelastic neutron scattering
• Macroscopic Quantum Coherence of the Spin Triplet in the Spin-Ladder Compound Sr14Cu24O41
• Sound modes in composite incommensurate crystals

Cited by in corpus (7)

• Magnon and Phonon Dispersion, Lifetime and Thermal Conductivity of Iron from Spin-Lattice Dynamics Simulations
• Simplest phonons and pseudo-phonons in field theory
• Effects of Grain Boundaries and Defects on Anisotropic Magnon Transport in Textured Sr14Cu24O41
• Glass-Like Thermal Conductivity in Nanostructures of a Complex Anisotropic Crystal
• Excess speicific heat of the gapped sliding phonons in the incommensurate composite crystal Sr${}_{14}$Cu${}_{24}$O${}_{41}$
• Interplay between trimer structure and magnetic ground state in Ba5Ru3O12 probed by Neutron and muSR techniques
• Effects of Ca substitution on quasi-acoustic sliding modes in Sr${}_{14-x}$Ca${}_x$Cu${}_{24}$O${}_{41}$