Description of the thesis topic

The PhD fellow will fabricate vertical optical microcavities based on dielectric distributed Bragg reflectors and embedding 2D materials, either as monolayers or building 2D heterostructures. He/she will further implement internal electrical contacts so as to enable an electrostatic control of the exciton-photon interaction. Once fabricated, the PhD fellow will perform the optical characterization of the microcavities in the linear regime in order to determine the coupling strength between the excitonic and photonic resonances, and assess the achievement of the strong-coupling regime. Subsequently, polaritons nonlinearities, generated by pulsed optical pumping, will be harnessed to study polariton hydrodynamics in combination with topological and quantum effects.

The PhD fellow will be physically based in the School of Physical and Mathematical Sciences, at NTU, but will interact weekly with the theoreticians of the project (in Singapore and in France), as well as with experimentalists at the Center for Quantum Technologies (NUS, Singapore) and CRHEA (Univetsité Côte d'Azûr-CNRS, France). The PhD degree will be awarded by the Université Côte d'Azûr, in France.

The PhD fellow will perform the fabrication of the samples either inside glovebox or in a clean-room environment (in one of NTU's clean-rooms). He/she will subsequently characterize the optical properties of the samples by reflectivity, transmission and photoluminescence experiments, both at room- and low-temperature. Finally, the PhD fellow will report the results to the project consortium and will participate in the dissemination of the results through conference presentations and writing and publication of scientific articles.

- Background in condensed-matter physics, quantum optics or materials science will be a plus, though not necessary.
- Hand-on experience in nanofabrication or optical characterization techniques will be a strong plus.
- Knowledge of basic programming will be useful.
- Excellent analytical, organizational, and communication skills.
- Capacity to develop and nurture crossed-disciplinary networks, in particular at international level.
- Creativity and ability to think out of the box.

- Opportunity to work on a strategic project and to play an instrumental role in the structuration of the burgeoning field of quantum communications.
- Opportunity to supervise Final Year students and interns, and freedom to define and execute workplans.
- Active collaborations in France and in Singapore within highly stimulating environments.
- Excellent networking opportunities with leading experts from academia.
- Excellent working conditions with competitive salary and benefits (depending on the origin and background of the candidate).

Work Context

MOIRE++: “Engineering light-matter coupling in TMD-based optical microcavities” is a four-year project funded by the French National Research Foundation (ANR). The main objective of the project is to explore the physics of light-matter coupling between excitons in transition metal dichalcogenides materials and photons confined in optical microcavities, and engineer the coupling therein thanks to an external electrical control knob. From the technological point of view Moiré++ aims to:

O1. Fabricate vertical optical microcavities based on dielectric DBRs and embedding TMDs that display photonic quality factors Qs>3000 in the first year of the project and that attain our final target of Q~10000.

O2. Implement electrical control of polaritons in monolayer TMDs and Moiré superlattices embedded in vertical microcavities. First we will introduce a vertical electrostatic field, which will tune continuously the exciton oscillator strength and, thereby, the Rabi splitting. Second, we will introduce an in-plane electrostatic field to “guide” polaritons electrostatically in TMD heterostructures.

while from the fundamental point of view we plan to demonstrate:

O3. Emergence of quantum correlations from interacting Moiré polaritons. This will require to have very-high quality van der Waals heterostructures to be able to couple a reduced number of excitons to the cavity mode, and to have an optical cavity with a Q better than any TMD-containing optical cavity today.

O4. Study of a nonlinear topological system. The combination of exciton nonlinearities with the topological properties of the cavity photonic mode and of the Moiré electronic band structure will be realized in the same system. Confrontation between theory and experiment will give us hints on the interplay between excitonics and photonics thanks to their effects on spin-valley-optical Hall phenomena.

The consortium gathers MAJULAB (CNRS, Université Côte d'Azûr, Sorbonne Université, NTU and NUS) (Université Côte d'Azûr-CNRS), INSTITUT PASCAL (Université Cerlmont-Auvergne, CNRS) and CRHEA (Université Côte d'Azûr-CNRS).

The teams of Prof. Jesus Zuniga Perez (CNRS) has been working on the field of polaritonics for more than 15 years [1], developing large quality factors microcavities, demonstrating polariton Bose-Einstein condensation at room-temperature [2] and the first polariton lasers based on fast-propagating waveguide polaritons [3,4]. Since 2022, the team of Prof. Jesus Zuniga Perez and of Prof. Weibo Gao have established a collaboration to investigate strong-coupling in microcavities embedding transition metal dichalcogenides, which provide excitons with very large oscillator strengths and binding energies. In this context, they have built a tuneable external microcavity setup at NTU, which will be thoroughly used during the PhD and which is currently managed by a research fellow who will strongly participate in the project.

MajuLab is a joint international lab whose signatory institutions are the French Centre National de la Recherche Scientifique (CNRS), the Universite Cote d'Azur (UCA), Sorbonne Universite (SU), the National University of Singapore (NUS) and the Nanyang Technological University (NTU). Since its creation in 2014, this French-Singaporean photonic and quantum centre has been instrumental in initiating and sustaining long term synergies between the French and the Singaporean ecosystems. The research fellow will be physically based in the School of Physical and Mathematical Sciences, at NTU, but will need to contribute to work at the Center for Quantum Technologies, NUS. He/she will engage in the fast-paced Singaporean ecosystem, a multicultural hub and Asian leader in deep tech.

Constraints and risks

The PhD fellow will carry out much of the work inside an optical laboratory, with a large number of laser sources. Thus, the PhD fellow will need to follow the strict security rules established by NTU concerning the use of laser sources.