Dear Friends, On Thursday, January 31st, there will be an ITAMP topical lunch discussion. Tea Room (P-226) @ CfA (60 Garden Street) Time: 12:00-1:30 As always pizza will be served. Speaker: Matthias Punk Title: Mobile impurity near the superfluid-Mott insulator transition in two dimensions Abstract: In this talk I'm going to discuss transport properties of an impurity atom coupled to bosons in a 2d optical lattice at integer filling near the superfluid-Mott insulator transition. Calculating transport coefficients near quantum critical points remains a challenging problem in theoretical condensed matter physics, and I will start the talk by giving an overview of the basic problems and open questions in this field. After that I'm going to focus on the impurity diffusion constant, which can be measured directly in experiments with quantum gas microscopes, and which exhibits some unexpected properties near the superfluid-Mott insulator critical point. Looking forward to seeing you there, Charles Mathy