• Jun 02 2015

    Upcoming theory seminars: "Comments on the scattering equations" by C Kalousios AND "Quantum quench of Kondo correlations in optical absorption" by J. von Delft

    Dear All,

    Next week the The Mandelstam and National Institutes for Theoretical Physics will host two seminars.

    The second seminar will also be of particular interest to colleagues in Experimental Condensed Matter Physics and Optics.

    All are welcome and we look forward to seeing you there.

    Seminar 1:

    Date and Time: Tuesday 2 June, 13:20

    Venue: P216

    Speaker: Chrysostomos Kalousios (ICTP South American Institute for Fundamental Research)

    Title: "Comments on the scattering equations"

    Abstract: I will present the latest developments and ideas in calculating scattering amplitudes of massless theories in arbitrary dimensions using the formalist of the scattering equations.

    Seminar 2:

    Date and Time: Thursday 4 June, 12:00

    Venue: P216

    Speaker: Jan von Delft (LMU, Munich)

    Title: "Quantum quench of Kondo correlations in optical absorption"
    Nature, 2011, 474, 627

    Abstract: The interaction between a single confined spin and the spins of a Fermionic reservoir leads to one of the most spectacular phenomena of many body physics - the Kondo effect. We study how Kondo correlations between the confined and reservoir spins emerge or disappear after a quantum quench. To this end, we consider a single semiconductor quantum dot, tunnel-coupled to a degenerate electron gas, that is subjected to a quantum quench, induced by the sudden creation of an exciton via optical absorption. Depending on initial conditions, the quench can be used to turn the Kondo effect either on or off. The evolution of Kondo correlations after such a quench can be read o ff from the absorption lineshape and understood in terms of the three fixed points of the single-impurity Anderson model. At low temperatures the line-shape is dominated by a power-law singularity, with an exponent that depends on gate voltage and, in a universal, asymmetric fashion, on magnetic eld, indicative of a tunable Anderson orthogonality catastrophe. -- We will also report on the observation of the Kondo effect in optical absorption measurements. By inferring the characteristic power law exponents from the experimental absorption line-shapes, we detect quantitative signatures of the Anderson orthogonality catastrophe that arises when the Kondo effect is turned on and a free Fermi sea evolves to a screened Kondo singlet. Our study demonstrates that optical measurements on single artificial atoms offer new perspectives on many-body phenomena previously studied exclusively using transport spectroscopy.

    Kind regards
    Izak Snyman