EPFL, Switzerland

报告摘要:

In few-layer 2D semiconductors, the spin, valley, energy, and spatial wavefunctions of Coulomb bound electrons and holes can be widely engineered to form the emerging layer-hybrid excitons. In the first part, I will discuss the ground (1s) and excited state (2s) momentum direct (K-K) hybrid dipolar excitons (IX) in bi- and tri-layer 2H-MoSe₂, which exhibit the layer engineered static dipole as well as the exciton g-factor, and their coupling with the intralayer exciton states. Moreover, we report the coexisting dipolar and quadrupolar exciton (QX) states in bilayer MoSe₂. The QX shows a distinct quadratic Stark shift with unique magneto-optical properties, in consistence with the 4-particle picture of coupled spin-triplet IXs with opposite permanent dipole moments.

In the second part I will present an ambipolar excitonic transistor based on momentum indirect (K-Λ) hybrid IX in bilayer WSe₂. We achieved the in-plane field-controlled lateral drag of layer-hybridized trions, characterized by PL and spatial imaging. We exploit the vertical field induced switch of IX transitions to enhance their lateral field-induced drag. Moreover, we unveil the different transport mobilities of positive and negative trions. Our results, supported by microscopic theories, promote the few-layer 2D semiconductors as promising platform to study the electrically controlled many-body physics as well as to develop novel excitonic and photonic devices.

[1] Shun Feng, et. al, Highly Tunable Ground and Excited State Excitonic Dipoles in Multilayer 2H-MoSe₂, Nat. Commun. 15, 4377 (2024).

[2] Shun Feng, et. al, Quadrupolar and Dipolar Excitons in Bilayer 2H-MoSe₂, Submitted, 2024.

[3] Shun Feng, et. al, Field-effect directional transport of layer-hybridized trions in a bilayer semiconductor, Submitted, 2024.

报告人简介:

Dr. Shun FENG received his doctorate in Physics from Nanyang Technological University in 2019 (supervisor: Ting Yu). After graduation, he worked as a postdoctoral researcher in the quantum materials optics group (2020-2023, supervisor: Brian Gerardot at Heriot-Watt University, UK) and nanoelectronics group (2023-now, supervisor: Andras Kis at EPFL, Switzerland). His main research direction is manipulating the optical and optoelectronic properties of 2D materials. He realized the modulation in the excitonic luminescence, absorption, transport, photocurrent, and valleytronic properties of 2D materials through electric fields, physical/chemical doping, and layer engineering. In the past five years, he published as the first author in journals such as Nat. Commun. (x2), Small, Adv. Opt. Mater, etc. During his PhD, he won several national conference awards, and during his postdoctoral training he was awarded the prestigious EU Marie Curie Individual Fellowship, and managed funding of more than 200,000 Euros.

邀请人：杜罗军（82647052）