Event
Ph.D. Research Proposal Exam: Supratik Sarkar
Monday, August 12, 2024
2:00 p.m.
Atlantic building room# ATL 3332
Maria Hoo
301 405 3681
mch@umd.edu
ANNOUNCEMENT: Ph.D. Research Proposal Exam
Name: Supratik Sarkar
Committee:
Professor Mohammad Hafezi (Chair)
Professor Ronald Walsworth
Professor Carlos A. Rios Ocampo
Date/time: August 12, 2024 at 2pm
Location: Atlantic building room# ATL 3332
Title: Many-body physics in two-dimensional semiconductors
Abstract:
In the last decade two-dimensional semiconductors, in particular transition metal dichalcogenides (TMDs), have seen a major surge in interest due to the possibility of studying a myriad of condensed matter phenomena in such systems. The strong Coulomb interaction, momentum-direct excitons with large binding energy, and spin-valley locking in TMDs combined with the ability to create heterostructures by simply stacking monolayers makes it an ideal test bed to study a plethora of many-body physics. In this thesis proposal, we aim to facilitate the study of many-body physics in such systems using the toolbox of light-matter interaction.
First, we demonstrate the formation of highly compact planar nanocavity using two atomically thin layers of TMD as mirrors [1]. Remarkably, we show how the excitonic nature of the mirrors enables the formation of chiral and tunable optical modes upon the application of an external magnetic field. Moreover, the cavity can be switched on/off by simply applying a gate voltage. Additionally, the cavity also has a flat dispersion, thereby making it robust to the angle of incident light and enhancing light matter interaction. Our work establishes a new regime for engineering intrinsically chiral sub-wavelength optical cavities and opens avenues for realizing spin-photon interfaces and exploring chiral many-body cavity electrodynamics.
Second, we demonstrate the formation of a Mott insulator in a hybrid Bose-Fermi Hubbard model implemented in a type-II TMD moiré heterostructure [2]. We independently tune the bosonic and fermionic population in the resultant moiré lattice and study the optical signatures of the strongly interacting Mott insulating state using traditional reflection, photoluminescence and diffusion measurements. Our system provides a controllable approach to the exploration of quantum many-body effects in the generalized Bose-Fermi Hubbard model.
Third, we demonstrate the formation of superlattices in a monolayer of TMD instead of a moiré heterostructure using a near-field metasurface plasmon polariton (MPP) pump below the diffraction limit [3]. We implement a non-local pump-probe scheme to study the spatially modulated AC Stark shift induced by the MPPs. We show almost two orders of magnitude increased efficiency compared to its free space counterpart and spatial resolution far below the diffraction limit. Our work provides a new platform to study light-induced phenomena in condensed matter systems. Moreover, the nonlocal pump-probe scheme also solves problems like pump-induced noise and thermal effects ubiquitous to traditional pump-probe spectroscopy.
Finally, we propose the optical control of fundamental properties of matter like tunneling strength and exchange interaction using a two-photon Raman process in a type-I TMD heterostructure. Our proposed scheme aims to optically control the tunneling strength, and hence the effective exchange interaction of charges in a TMD bilayer. Moreover, this can allow us to directly measure the interaction strength of individual charges in these systems for the first time. Such a degree of controllability of condensed matter systems will facilitate taking advantage of Floquet engineering for quantum simulation of exotic materials.
[1] Daniel G Suárez-Forero*, Ruihao Ni*, Supratik Sarkar*, Mahmoud Jalali Mehrabad*, Erik Mechtel, Valery Simonyan, Andrey Grankin, Kenji Watanabe, Takashi Taniguchi, Suji Park, Houk Jang, Mohammad Hafezi, You Zhou. Chiral optical nano-cavity with atomically thin mirrors. arXiv:2308.04574 (2023).
[2] Beini Gao*, Daniel G Suárez-Forero*, Supratik Sarkar*, Tsung-Sheng Huang, Deric Session, Mahmoud Jalali Mehrabad, Ruihao Ni, Ming Xie, Jonathan Vannucci, Sunil Mittal, Kenji Watanabe, Takashi Taniguchi, Atac Imamoglu, You Zhou, Mohammad Hafezi. Excitonic mott insulator in a Bose-Fermi-Hubbard system of moiré WS2/WSe2 heterobilayer. Nature Communications, 15(1):2305 (2024).
[3] Supratik Sarkar*, Mahmoud Jalali Mehrabad*, Daniel G. Suárez-Forero*, Liuxin Gu*, Christopher J. Flower, Lida Xu, Kenji Watanabe, Takashi Taniguchi, Suji Park, Houk Jang, You Zhou, Mohammad Hafezi. Sub-wavelength optical lattice in 2D materials. arXiv: 2406.00464 (2024).
