Nonlinear nanoelectrodynamics of a Weyl metal
Yinming Shao, Ran Jing, Sang Hoon Chae, Chong Wang, Zhiyuan Sun, Eve Emmanouilidou, Suheng Xu, Dorri Halbertal, Baichang Li, Anjaly Rajendran, Francesco L. Ruta, Lin Xiong, Yinan Dong, Alexander McLeod, Sai Sunku, James Hone, Joel E. Moore, Joe Orenstein, James G. Analytis, Andrew J. Millis, Ni Ni, Di Xiao, D. N. Basov
Abstract
Significance Nonlinear optics in topological semimetals is a burgeoning field of research with an expanding list of new materials but limited choice of probes. We devised, modeled, and implemented an approach for investigating nonlinear optics at the nanoscale with a metallic tip. Far-field nonlinear optics are diffraction-limited and probe the in-plane response only. Our tip-based approach circumvents the diffraction limit and provides strong field enhancement for both in-plane and out-of-plane fields. We therefore gain access to complete nonlinear tensors including components not attainable before. One immediate application of our approach is the separation of surface state and bulk nonlinear responses in Weyl semimetals. Applying near-field probes to topological semimetals constitutes a new paradigm of research on nanoscale nonlinearity.