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Why are electron repulsions important?


Title : Why are electron repulsions important?
Speaker : Speaker : Prof. Ramasesha, Indian Institute of Science, Bangalore.
Date : 30/01/2019, 5:30 PM , C.V Raman Hall, Second Floor.


In this talk, I will discuss the failure of molecular orbital theory in simple diatomic molecules. These include the incorrect dissociation of hydrogen molecule, wrong ordering of energy levels in nitrogen molecule to mention a few. I will discuss how incorporating electron correlations leads to the correct picture. I will show how the physics of Mott-Hubbard transition is similar to the physics of dissociation of the hydrogen molecule. I will then discuss the manifestation of electron correlations in polyacetylene, a simple conjugated polymer. I will briefly discuss how spin waves and excitonic states arise in strongly correlated systems.  The rich physics generated by incorporation of electron correlations, correlated electron states of conjugated polymers, importance of energy level ordering and its implications to device physics will be discussed. Model Hamiltonians employed in these studies as well as methods of solving these many-body Hamiltonians will also be touched upon.