Date: 2020-7-3

Time: 14:00-15:00

Venue: Tencent Meeting

Speaker: Dr  Deepak Bahadur Karki (Division of Quantum State of Matter)

Abstract:

A multi-orbital quantum impurity connected to several reservoirs of conduction electrons can lead to a Kondo effect exhibiting multi-stage screening. While the single-stage Kondo paradigm is more or less well understood, the multi-stage version of Kondo effects is at the focus of present research in the field of strongly correlated systems. Theoretically understanding the transport properties of the strong-coupling regime resulting from the multi-stage mechanism had been an open problem for more than two decades, because, in contrast to standard impurity models, not one but many non-trivial phase shifts are involved. Recently, we developed a multi-stage transport formalism based on a local Fermi liquid theory in combination with the non-equilibrium Keldysh technique and conformal field theory. In this talk, I will introduce, pedagogically, the multi-color Fermi liquid theory of quantum transport through multi-level Kondo impurity. As an application of our theory, the transport properties of single channel SU(N) and two-stage Kondo effects will be discussed. In addition, the application parts of multi-color theory will be focused for the resolution of the longstanding experimental puzzle of the thermotransport through the Kondo impurity at the strong coupling regime.

About the speaker:

Dr. Deepak Karki received his postgraduate diploma in Condensed Matter and Statistical Physics from the Abdus Salam International Centre for Theoretical Physics (ICTP), Italy in 2015. Subsequently, he joined to the Condensed Matter Theory section of the International School for Advanced Studies (SISSA), Italy for his PhD and defended his thesis on Multi-stage Kondo effects at the end of 2019.Deepak’s research mainly focuses on the efficient control of transport behavior through nano-sized quantum  devices in the presence of strong electron-electron interactions and resonance scattering such as the Kondo correlated systems. His main expertise are analytical calculations using in- and out-of-equilibrium many-body quantum field theory techniques such as scattering theory, renormalization group, Bethe Ansatz, Green-Kubo formalism, conformal field theory, bosonization and Keldysh formulation.