Abstract
The concept of quasi-particles forms the theoretical basis of our microscopic understanding of emergent phenomena associated with quantum-mechanical many-body interactions. However, the quasi-particle theory in disordered materials has proven difficult, resulting in the predominance of mean-field solutions. Here, we report first-principles phonon calculations and inelastic X-ray and neutron-scattering measurements on equiatomic alloys (NiCo, NiFe, AgPd, and NiFeCo) with force-constant dominant disorder—confronting a key 50-year-old assumption in the Hamiltonian of all mean-field quasi-particle solutions for off-diagonal disorder. Our results have revealed the presence of a large, and heretofore unrecognized, impact of local chemical environments on the distribution of the species-pair-resolved force-constant disorder that can dominate phonon scattering. This discovery not only identifies a critical analysis issue that has broad implications for other elementary excitations, such as magnons and skyrmions in magnetic alloys, but also provides an important tool for the design of materials with ultralow thermal conductivities.
| Original language | English |
|---|---|
| Article number | 4 |
| Journal | npj Computational Materials |
| Volume | 6 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1 2020 |
Funding
This work was supported as part of the Energy Dissipation and Defect Evolution (EDDE), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, and Basic Energy Sciences under contract number DE-AC05-00OR22725. This research used resources of the Advanced Photon Source, a DOE Office of Science User Facility operated by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Beamline support by Ayman Said of the Advanced Photon Source and Songxue Chi of the High Flux Isotope Reactor is acknowledged. This research also used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This research used resources of Oak Ridge National Laboratory’s Compute and Data Environment for Sciences (CADES) and the Oak Ridge Leadership Computing Facility, which is a DOE office of Science User Facility supported under Contract DE-AC05-00OR22725. Work at MPI was supported by Deutsche Forschungsgemeinschaft (Germany) within the priority programme SPP 1599. L.L. and T.B. acknowledge support from the U.S. Department of Energy, Office of Science, Basic Energy Sciences, and Materials Sciences and Engineering Division. B.D. and S.M. acknowledge Dr. Fritz Körmann and Dr. Yuji Ikeda for fruitful discussions. S.M. is grateful to Dr. Xin Huang and Dr. Lisha Fan for graphic support.