CAREER: GHz imaging of strongly correlated and topological phenomena in moire materials

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Nontechnical abstract: A major thrust of condensed matter physics concerns the discovery of new electronic states in emerging quantum materials. A prominent example is the rapidly expanding class of topological insulators, which are characterized by conductive edges that enclose an insulating interior. This project sheds light on exotic phenomena that can arise from the interplay of correlations and topology in two-dimensional (2D) materials and harnesses these novel phases to build the next generation of quantum devices. The key to our approach is use of a novel low temperature imaging technique, which detects the unique fingerprint of the conducting edge currents at high frequencies and spatially disentangles them from trivial states in the interior of the material. Emerging topological states in 2D materials could potentially be harnessed in the future to enable new quantum technologies, including exceptionally robust forms of quantum computing in which environmental noise is strongly suppressed. To train the next generation of scientists and engineers, this project also develops a new Quantum Materials and Devices teaching module, which equips students with an interdisciplinary toolbox spanning materials and device preparation, measurements in a cryogenic environment, data analysis, and technical writing skills. To integrate research and outreach, the principal investigator aims to organize a science-themed public art exhibit, which presents the microscopy of quantum materials as an exciting new frontier for scientific exploration.Technical abstract: The aim of this project is to investigate the microscopic nature of collective phenomena arising from the interplay of interactions and topology in van der Waals (vdW) heterostructures and magnetic topological insulators. By pushing the frontiers of microwave impedance microscopy (MIM) to ultra-low temperatures, this research strives to detect the unique signature of plasmonic excitations in magnetic topological insulators and construct a microscopic picture of dissipation along the edge. Building upon recent developments on the materials front, a complementary thrust focuses on engineering correlated topological states in vdW heterostructures by tuning the angular rotation between layers and the electrostatic environment. In particular, the project features a focused investigation of Moire superlattices in twisted bi-layer MoTe2, in which narrow bands are predicted to give rise to a family of many-body states, including quantum anomalous Hall and antiferromagnetic insulators. These experiments utilize electronic transport and microwave imaging methods to construct a comprehensive phase diagram of ordered states, shedding light on the key symmetry-breaking mechanisms. This research builds the foundation for GHz characterization of topological states in emerging quantum materials; it complements the materials discovery effort in the synthesis community by enabling fast characterization of chiral edge states in thin films, multi-domain systems, and devices. In the future, this milliKelvin imaging capability could potentially be used for local readout of topological states in device platforms for quantum computing applications.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.