|Practice Talks: Baranger/Finkelstein groups
Filter by: 03-21-2011 03-23-2011 03-24-2011 03-25-2011 clear
||T22.00009 : Mesoscopic Anderson Box: Connecting Weak to Strong Coupling
Dong E. Liu, Sebastien Burdin, Harold U. Baranger, Denis Ullmo
Both the weakly coupled and strong coupling Anderson impurity problem are characterized by a Fermi-liquid theory with weakly interacting quasiparticles. In an Anderson box, mesoscopic fluctuations of the effective single particle properties will be large. We study how the statistical fluctuations in these two problems are connected. We use random matrix theory and the slave boson mean field approximation (SBMF, at low temperature) to address this question, obtaining the following results. First, for a resonant level model such as results from the SBMF approximation, we find the joint distribution of energy levels with and without the resonant level present. Second, if only energy levels within the Kondo resonance are considered, the distribution of perturbed levels collapse to one universal form for both GOE and GUE for all values of the coupling V. Finally, a purely Fermi liquid method is developed for calculating the perturbed levels within the Kondo resonance. Comparing the levels that result to those of the SBMF, we find remarkable agreement.
We fabricate lead (Pb) contacts to graphene that allow us to observe supercurrent in the Pb-graphene-Pb structure up to temperatures of $\sim $3K. The measured critical current is much smaller than a naive expectation based on calculations for a superconductor-insulator-superconductor (S-I-S) junction. Hysteresis is seen in the switching current despite the fact that the junction is made to be overdamped. The behavior of the Pb-graphene-Pb structure is qualitatively explained by considering it as an S-N-S junction.
A27.00005 : Quantum Transport of Strongly-Correlated Photons in Waveguide QED
We present an exact solution of the quantum transport problem of multi-mode photons in a waveguide quantum electrodynamics (QED) system, which may be realized in a variety of circuit-QED, plasmonic, photonic, or cold-atom contexts. The bosonic modes are strongly coupled to a local atomic or qubit system, which can be a two-level, Gamma-type three-level, or N-type four-level system. We show that strong coupling produces dramatic quantum optics effects. In particular, multi-photon bound states emerge in the scattering of two or more photons. Such bound states have a large impact on the transport of coherent-state wave-packets. For a two-level system, the single-photon probability is suppressed while multi-photon probabilities are strongly enhanced, resulting in non-classical statistics. For a three-level system, as one tunes the coupling strength and the control field, the transmitted light can show bunching or antibunching, indicating effective attractive or repulsive interactions. Finally, for a N-type four-level system, we demonstrate that the multi-photon components can be largely suppressed, leading to a potential single-photon filter.
Henok Mebrahtu, Ivan Borzenets,
We study conductance through a resonant level in a single-walled carbon nanotube quantum dot embedded in a dissipative environment. The dissipation is provided by environmental modes in the nanotube leads and the strength of the dissipation is experimentally controlled in several samples. At base temperature, dissipation suppresses the resonant tunneling peak height while maintaining resonant level width. We also observe a regime where the height and the width of a conductance peak demonstrate qualitatively different energy scaling.
X34.00005 : Programmable Nanofabrication of Nanoparticle Assemblies of arbitrarily Shapes on DNA Templates
We present a method for producing metallic structures with nanoscale dimensions and programmable design. Rectangular ``DNA origami'' structures ($\sim $90x70nm) were modified to have uniquely coded binding sites and adsorbed onto silicon dioxide substrates. Gold nanoparticles functionalized with a complimentary DNA sequence were attached to these binding sites in a highly controllable fashion. The seed nanoparticles were then enlarged (and even fused, if desired) by a silver reduction chemistry. Using this method we constructed a variety of metallic structures, including parallel wires, H-shapes, and rings. Due to the flexibility of the design and the multiply parallel nature of the method, these structures may offer great promise for plasmonic applications.