Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session T37: Quantum geometric advantage in opto-electronics
11:30 AM–2:30 PM,
Thursday, March 9, 2023
Room: Room 233
Sponsoring
Unit:
DCMP
Chair: Mark Rudner, University of Washington
Abstract: T37.00002 : Moiré quantum geometry: from fundamentals to intelligent sensing*
12:06 PM–12:42 PM
Presenter:
Fan Zhang
(UT Dallas)
Author:
Fan Zhang
(UT Dallas)
First, I will introduce that the superlattice gap of twisted bilayer graphene is associated with unusual Z2 band topology originating from the (single-state) quantum metric instead of (abelian) Berry curvature, by using K-theory, nonlocal transport, and superconducting quantum interferometry. This resolves the puzzle of flat-band superfluid weight in the magic-angle limit. Further, I will show that for graphene moiré systems the linear resonant optical responses and second-order bulk photovoltaic effects (BPVE), as manifestations of the Hermitian (double-state) metric and connection, are particularly strong and tunable in the infrared range. In the BPVE rendered by moiré quantum geometry, not only are the phase and amplitude of the photovoltage substantially dependent on the excitation light polarization, but they are also highly tunable by external electric fields. This has enabled us to utilize the BPVE as an encoder and a convolutional neural network as a decoder to achieve full-Stokes polarimetry together with wavelength and power detections simultaneously using only one single moiré device with a subwavelength footprint of merely 3 × 3 μm2 .
These results not only reveal the significant roles of moiré engineered quantum geometry in strongly correlated phases and in tunable light–matter interactions but also identify a pathway for future intelligent quantum geometric sensing technologies in an extremely compact, on-chip manner across a broad spectral range.
*F.Z. acknowledges the Texas Advanced Computing Center (TACC) for providing resources that have contributed to the research results. F.Z. acknowledges support by the Army Research Office under grant number W911NF-18-1-0416 and by the National Science Foundation under grant numbers DMR-1945351 through the CAREER program, DMR-1921581 through the DMREF program, and DMR-2105139 through the CMP program.
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