Recent Research

Revealing topological surface states via nonlinear and nonreciprocal transport effects

Post Date:2024-02-21

One of the challenging subjects in topological systems is to identify the charge transport signatures associated with the unusual surface states due to nontrivial band topology. In a recent international collaborating work led by Dr. Wei-Li Lee and Prof. Guang-Yu Guo, an unusual large nonreciprocal and nonlinear charge transport effects (NRTE) in both longitudinal and transverse channels were observed in thin films of topological ferromagnetic Weyl metal SrRuO3 (SRO). These behaviors align with a proposed scenario of an effective Berry curvature dipole originating from Fermi-arc surface states accompanied by 1D chiral edge modes, which is supported by electronic band structure calculations. Our findings not only highlight the significance of NRTE as a charge transport probe for topological surface states with a broken inversion symmetry but also feature potential applications in nonreciprocal electronics and nonlinear optics using topological materials. The complete data and analyses have been recently accepted for publication at Physical Review X (
Uddipta kar, Elisha Lu, Akhilesh Singh and P.V. Sreenivasa Reddy are the co-first authors. The SRO thin film growth, device fabrication and transport measurements were carried out by Dr. Wei-Li Lee’s group at IoPAS and Prof. I-Chun Cheng’s group at NTU. The electronic band structure calculations were performed by Prof. Guan-Yu Guo’s group at NTU and Prof. Wei-Cheng Lee’s group at SUNY Binghamton. The optical SHG measurements were performed by Prof. David Hsieh’s group at Caltech. The SRO thin film structural characterizations were performed by Director Chia-Hung Hsu’s group at NSRRC.

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