Integrated Calendar

The nuclear neutron-proton contact is introduced, generalizing Tan's work, and evaluated from medium energy nuclear photodisintegration experiments.
To this end we reformulate the quasi-deuteron model of nuclear photodisintegration and establish the bridge between the Levinger constant and the contact. Using experimental evaluations of Levinger's constant we extract the value of the neutron-proton contact in finite nuclei and in symmetric nuclear matter. Assuming isospin symmetry we propose to evaluate the neutron-neutron contact
through measurement of photonuclear spin correlated neutron-proton pairs.

Topological insulators (TIs) are novel materials that do not conduct elec-tricity in their bulk but possess exceptional conducting electronic states on their surface. These surface electrons have a number of highly unusu-al characteristics: (i) they behave like massless relativistic particles similar to photons (ii) their spin is locked perpendicular to their momentum and (iii) this state is robust against moderate disorder. Understanding and characterizing unique properties of these materials can lead to novel ap-plications such as current induced magnetization or extremely robust quantum memory bits. In this talk, I will first give a brief introduction to these materials and then describe our recent experiments in which we used ultrashort laser pulses to probe and control properties of the topo-logical surface states. Utilizing the short duration of these pulses, we suc-ceeded in capturing femtosecond movies of the electronic energy bands in a three dimensional manner. These movies reveal an exotic hybrid state between electrons and light which was predicted theoretically but has never been observed in solids before.