The charge of protons, neutrons and electrons are different from each other. This is the origin of various chemical elements and all the matter around us. The electrons with negative charge form orbitals around a nucleus and then attract another nucleus.

All the electrons have the same character; there is no difference between them. However, once the Coulomb interaction works between the electric charges, diverse characters of materials appear.

Interesting properties of metallic, insulating, magnetic, and superconducting states, etc. are generally originated from quantum many body interactions. To understand the fundamental properties of solid state materials we are developing new theoretical concepts and computational methodologies. Solving quantum many body problems is the heart of solid state physics.