1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
2. State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, P.R. China
3. MajuLab, CNRS-UCA-SU-NUS-NTU
International Joint Research Unit, UMI 3654, Singapore 639798
4. Laboratoire Pierre Aigrain, Département de physique de l’ENS, Ecole normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Paris 75005, France
5. NOVITAS, Nanoelectronics Center of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798