Atomic-scale Imaging of Novel Electronic States in Kagome Superconductors

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Non-technical abstract: The so-called kagome material structure is characterized by the arrangement of atoms residing in the corners of corner-sharing triangles. This structure has emerged as a rich platform to study novel phenomena. Due to the geometry of the kagome structure, electrons in these systems can have distinct characteristics that are rarely found in other materials. However, the underlying physical properties of kagome systems are still poorly understood at a fundamental level. This project aims to understand the exotic properties of a new family of kagome materials. To accomplish this, the researchers employ modern experimental methods of scanning tunneling microscopy and spectroscopy. The project focuses on studying the effects of magnetic field, strain, and chemical composition change on the properties of these systems. The research aims to deepen the fundamental understanding of kagome materials, and establish the foundation for their eventual use and applications in technology. Integrated research and education activities aim to train and educate students via establishing outreach events in local schools, and by giving lab tours. To motivate young students to pursue science careers, the PI provides research opportunities for high-school students and underrepresented groups in his lab. Technical abstract: The kagome lattice of transition metal atoms offers an exciting platform to study electronic correlations in the presence of geometric frustration and nontrivial band topology. The recently discovered class of layered kagome metals AV3Sb5 (A=K, Cs or Rb), composed of a kagome net of Vanadium atoms, has generated significant interest in the community. There has been an avalanche of intriguing theories proposed and experimental phenomena observed, for example the observation of anomalous Hall response, various density waves, and a rare occurrence of superconductivity in a kagome system. This project focuses on using variable-temperature spectroscopic-imaging scanning tunneling microscopy to explore novel electronic phenomena in this new class of materials. Specifically, it aims to: (1) reveal the existence of electronic nematic phase in these materials, (2) uncover what is the spectroscopic origin of the surprising charge stripe phase, (3) provide a comprehensive atomic-scale insight into how the observed density waves and superconductivity evolve as a function of chemical doping, temperature and strain, (4) determine the effect of magnetic field on the electronic band structure to look for signatures of orbital moments, and (5) shed light on the nature of superconductivity and the existence of one-dimensional modes propagating along domain walls. The combination of in situ vector magnet and spectroscopic-imaging scanning tunneling microscopy provides a rare tool for direct band structure mapping as a function of vector magnetic field. The PI’s integrated research and education activities aim to impact a wide range of students via establishing outreach events in local middle and high schools, and giving lab tours. To motivate young students to pursue science careers, the PI provides research opportunities for high-school students and underrepresented groups in his lab.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.