Rydberg Exciton in Atomically Thin Semiconductor for On-chip Quantum Optoelectronics

Rydberg atom refers to a high energy atom with a size much larger than the atom at its lowest energy state. The large size of the Rydberg atoms enables strong interactions among themselves that can be exploited for quantum information science. Light excitation of semiconductors can generate positive and negative charges bound together, known as excitons.

The tightly bound exciton at the high energy state, known as Rydberg exciton, is an analogue to the Rydberg atom and shares many superior properties, such as the strong interaction. Rydberg excitons in traditional semiconductors are either not stable enough or difficult to be patterned and controlled. The atomically thin semiconductors known as transitional metal dichalcogenides (TMDCs), however, host robust excitons and usher in an exciting platform of manipulating Rydberg excitons in two-dimension (2D).

The Rydberg exciton in TMDCs also has a new quantum degree of freedom. We have recently developed a new measurement technique with high sensitivity to probe the largest 2D Rydberg exciton ever reported. In this proposal, we will pattern the atomically thin semiconductor so that we can control the in-plane electric field and study its interaction with the 2D Rydberg excitons.

We will also probe the strong interaction between Rydberg excitons, which will pave the way for a new platform for quantum information science. The integrated education components train the next generation workforce for semiconductors, nanoscale technology, optical science and engineering through research opportunities, curriculum development, and outreach activities, with a particular emphasis on educating and recruiting under-represented groups.

Both existing programs at Rensselaer Polytechnic Institute and newly developed outreach programs will be utilized to encourage K-12 students to study in the field of quantum information science and engineering.

Technical Description: Rydberg atoms refer to the atoms with the outer electron occupying the highly excited state with a very large principal quantum number n. The strong interaction between Rydberg atoms leads to nonlinear effects such as the Rydberg blockade, providing a promising route for quantum computing and simulation. Rydberg exciton, an excited state of the optically excited electron-hole pair, is a condensed matter analogue of the Rydberg atom and can be directly used for optoelectronic devices thanks to mature fabrication and control technologies of semiconductors.

Although high-order Rydberg excitons have been extensively studied in Cu2O crystals, it is difficult to pattern and control the Rydberg exciton in bulk semiconductors. Atomically thin semiconductors host robust exciton with large binding energy, which can also be efficiently controlled electrostatically, thereby opening doors to exciting opportunities for quantum optoelectronics.

Here we propose to construct high-quality monolayer transitional metal dichalcogenides (TMDCs) devices in which we fabricate an on-chip p-n junction. We also propose to probe and control the Rydberg excitons through our recently developed photocurrent spectroscopy techniques, with which we have shown unprecedented high order Rydberg excitons in monolayer WSe2 with n = 11.

We will investigate the Rydberg exciton’s sensitive response to the external electric and magnetic fields. We will also explore nonlinear effects and try to demonstrate the 2D Rydberg exciton blockade for the first time. This proposal will not only directly demonstrate a prototype of a quantum sensing device based on 2D Rydberg excitons but also paves the way for a ground-breaking platform to manipulate highly tunable 2D Rydberg excitons for quantum information science and engineering.

The closely integrated research and education components provide training opportunities for graduate, undergraduate, and K-12 students on advanced optical spectroscopy, nanoscale device fabrication, and quantum materials, with special emphasis on recruiting under-represented groups. This proposal also includes outreach programs for K-12 students, such as working with Troy Boys and Girls Club.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.