Center for Functional Nanomaterials Seminar

"Microwave Impedance Microscopy at Ultra-Low Temperatures and the Fractional Quantum Anomalous Hall Effect"

Presented by Mark Barber, Stanford University

Friday, June 6, 2025, 2:30 pm — Videoconference / Virtual Event (see link below)

Probing the local electronic landscape of quantum materials with high spatial resolution is essential for understanding and engineering emergent phenomena that underpin future quantum technologies. Microwave Impedance Microscopy (MIM), a scanning probe technique that measures tip-sample admittance in a non-contact geometry at microwave frequencies, can do just that. In this talk, I will outline the working principles of MIM and illustrate how it can be used to study the electronic properties of quantum materials. I will present our recent efforts imaging the newly discovered zero-field fractional Chern insulator (FCI) state in MoTe2, a lattice analog of the fractional quantum Hall effect (FQHE) realized without an external magnetic field. By tuning the carrier density, we observe the evolution between metallic and FCI states. The FCI phase exhibits a gapped, insulating bulk coexisting with a conductive edge, providing the first direct spatial observation of bulk-edge correspondence in a FQHE-like system. I will conclude with a discussion of our ongoing efforts to develop a dry dilution refrigerator-based scanning probe platform for ultra-low temperature, fast-turnaround multi-modal scanning probe microscopy which will open new avenues for studying fragile topological and correlated states of quantum mater.

Hosted by: Dario Stacchiola

Videoconference Instructions

Topic: Mark Barber: Virtual Seminar Time: Jun 6, 2025 02:00 PM Eastern Time (US and Canada) Join ZoomGov Meeting https://bnl.zoomgov.com/j/1612896349?pwd=tn8maFHwnPFnkOC0lUSLmE2cHibyfK.1 Meeting ID: 161 289 6349 Passcode: 790880 —- One tap mobile +16692545252,,1612896349#,,,,*790880# US (San Jose) +16469641167,,1612896349#,,,,*790880# US (US Spanish Line) —- Dial by your location • +1 669 254 5252 US (San Jose) • +1 646 964 1167 US (US Spanish Line) • +1 646 828 7666 US (New York) • +1 669 216 1590 US (San Jose) • +1 415 449 4000 US (US Spanish Line) • +1 551 285 1373 US (New Jersey) Meeting ID: 161 289 6349 Passcode: 790880 Find your local number: https://bnl.zoomgov.com/u/a5SasqebS —- Join by SIP • 1612896349@sip.zoomgov.com —- Join by H.323 • 161.199.138.10 (US West) • 161.199.136.10 (US East) Meeting ID: 161 289 6349 Passcode: 790880

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