STUDY OF ELECTRONIC STRUCTURES AND CORRELATIONS IN GRAPHENE USING OPTICAL SPECTROSCOPIES

Abstract

In this thesis we have explored graphene optical properties using various experimental techniques namely spectroscopic ellipsometry, vacuum ultraviolet reflectivity and ultrafast pump-probe technique. The main emphasis has been to study the optical conductivity (from infrared to vacuum ultraviolet) which gives information about graphene electronic structures as well as correlation effects present. Graphene samples on different substrates with varying dielectric constants as well as band-gaps are studied experimentally using the techniques mentioned. Our results show anomalous screening of many-body effects in graphene on a metal substrate as compared to the case of graphene on quartz. Another new and intriguing observation has been the nearly full transparency of graphene in ultraviolet region possibly due to Fano anti-resonance. Similarly, observation of a high energy resonant exciton in epitaxial graphene is another highlight which underlies the crucial role many-body effects play in graphene optical properties.