JQI Seminar - Michael Knap

Title:  Strongly Correlated Quantum States in Moiré Heterostructures

Abstract:  Recent experimental progress in realizing and controlling two-dimensional semiconductors has enabled the investigation of a vast class of strongly correlated states of matter, including correlated insulators and fractional quantum anomalous Hall states. Such states have been found in twisted moiré heterostructures of Transition Metal Dichalcogenides (TMD). In this talk, we discuss how excitons—bound states of electrons and holes—in TMD heterostructures can be used as in-situ probes of a periodic charge modulation of correlated insulators [1]. We analyze the dressing of excitons by electronic environments in the moiré lattice, leading to moiré polarons [2]. We investigate their renormalization in the vicinity of correlated insulators, where a giant enhancement of exciton diffusivity has been observed experimentally [3]. We then propose multilayer moiré structures in strong external magnetic fields as a novel platform for realizing highly tunable, frustrated Hubbard physics with topological order [4]. We show that these systems realize an exotic topological phase transitions from a bilayer integer quantum Hall state to a chiral spin liquid. The chiral spin liquid is encoded in the moiré layer acting as a pseudo spin degree of freedom. We show that an external magnetic field acts as an orbital field which explicitly breaks time reversal symmetry and thus stabilizes the chiral spin liquid. We discuss experimental signatures in the exciton response, and predict dynamical spectral functions that can be measured for example with scanning tunneling spectroscopy or quantum twisting microscopes. As the magnetic flux can be easily tuned in moiré systems, our approach provides a promising route toward the experimental realization and control of topologically ordered phases of matter. 

 

[1] Shimazaki, Kuhlenkamp, Schwartz, Smolenski, et al. Phys. Rev. X 11, 021027 (2021)

[2] Pichler, et al. [arXiv:2503.07712]

[3] Upadhyay, Suárez-Forero, Huang, et al. [arXiv:2409.18357]

[4] Kuhlenkamp, et al. Phys. Rev. X 14, 021013 (2024)

 

 

*You will need to bring your cell phone, so you can sign in using the QR code outside of ATL 2400.  You will need to submit your first and last name, email, and affiliation on the form by 11:15am to be able to get lunch after the seminar.  Lunch is first come, first served.*
 
At 4pm, there will be a tea in ATL 2117 for our speaker and students/postdocs - this is a chance to ask questions directly to our speaker. Refreshments will be served.