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Topological Singularity Induced Chiral Kohn Anomaly in a Weyl Semimetal



Thanh Nguyen, Fei Han, Nina Andrejevic, Ricardo Pablo-Pedro, Anju Apte, Yoichiro Tsurimaki, Zhiwei Ding, Kunyan Zhang, Ahmet Alatas, Ercan E. Alp, Songxue Chi, Jaime Fernandez-Baca, Masaaki Matsuda, David Alan Tennant, Yang Zhao, Zhijun Xu, Jeffrey W. Lynn, Shengxi Huang, Mingda Li


The electron-phonon interaction (EPI) is instrumental in a wide variety of phenomena in solid state physics, such as electrical resistivity in metals [1], carrier mobility, optical transition and polaron effects in semiconductors [2,3], lifetime of hot carriers [4–6], transition temperature in BCS superconductors [7], and even spin relaxation in diamond nitrogen-vacancy centers for quantum information processing [8–10]. However, due to the weak EPI strength, most phenomena have focused on electronic properties rather than on phonon properties. One prominent exception is the Kohn anomaly, where phonon softening can emerge when the phonon wavevector nests the Fermi surface of metals [11]. Here we report the discovery of a new class of Kohn anomaly in a topological Weyl semimetal (WSM), through inelastic scattering experiments on the WSM tantalum phosphide (TaP) and field-theoretical calculations. Compared to the conventional Kohn anomaly, the Fermi surface in a WSM is degenerated into multiple topological singularities of Weyl nodes, leading to a distinct nesting condition with chiral selection, a power-law divergence, and a non-negligible dynamical effect. Our work brings the concept of Kohn anomaly into WSMs and sheds light on elucidating the EPI mechanism in emergent topological materials.
Physical Review Letters


Electron-phonon interaction, Kohn Anomaly, Topological Weyl Semimetal, Inelastic Neutron Scattering


Nguyen, T. , Han, F. , Andrejevic, N. , Pablo-Pedro, R. , Apte, A. , Tsurimaki, Y. , Ding, Z. , Zhang, K. , Alatas, A. , Alp, E. , Chi, S. , Fernandez-Baca, J. , Matsuda, M. , Tennant, D. , Zhao, Y. , Xu, Z. , Lynn, J. , Huang, S. and Li, M. (2020), Topological Singularity Induced Chiral Kohn Anomaly in a Weyl Semimetal, Physical Review Letters, [online], (Accessed October 24, 2021)
Created June 10, 2020, Updated October 12, 2021