Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session Y1: Invited Session: New Perspectives on Kondo Systems |
Hide Abstracts |
Sponsoring Units: DCMP Chair: David Goldhaber-Gordon, Stanford University Room: Ballroom I |
Friday, March 22, 2013 8:00AM - 8:36AM |
Y1.00001: Frustration & Order in Kondo Lattice Systems Invited Speaker: Meigan Aronson |
Friday, March 22, 2013 8:36AM - 9:12AM |
Y1.00002: Visualizing heavy fermions emerging in a quantum critical Kondo lattice Invited Speaker: Pegor Aynajian In solids containing elements with $f$ orbitals, the interaction between $f$-electron spins and those of itinerant electrons leads to the development of low-energy fermionic excitations with a heavy effective mass. These excitations are fundamental to the appearance of unconventional superconductivity and non-Fermi-liquid behavior observed in actinide- and lanthanide-based compounds. We use spectroscopic mapping with the scanning tunneling microscope to detect the emergence of heavy excitations with lowering of temperature in a prototypical family of cerium-based heavy-fermion compounds. We demonstrate the sensitivity of the tunneling process to the composite nature of these heavy quasiparticles, which arises from quantum entanglement of itinerant conduction and $f$ electrons. Scattering and interference of the composite quasiparticles is used to resolve their energy--momentum structure and to extract their mass enhancement, which develops with decreasing temperature. The lifetime of the emergent heavy quasiparticles reveals signatures of enhanced scattering and their spectral lineshape shows evidence of energy--temperature scaling. These findings demonstrate that proximity to a quantum critical point results in critical damping of the emergent heavy excitation of our Kondo lattice system. [Preview Abstract] |
Friday, March 22, 2013 9:12AM - 9:48AM |
Y1.00003: Observation of Majorana-like Behavior at the Quantum Critical Point in a Resonant Level Coupled to a Dissipative Environment Invited Speaker: Gleb Finkelstein We investigate tunneling through a resonant level embedded in a dissipative environment, which suppresses tunneling rates at low temperatures. Specifically, the resonant level is formed in a carbon nanotube quantum dot, and the dissipative environment is realized by fabricating resistive leads. For the symmetric coupling of the resonant level to the two leads, we find that the resonant peak reaches the unitary conductance $e^2/h$ despite the presence of dissipative modes. Simultaneously, the width of the resonance tends to zero as a non-trivial power of temperature. We draw a connection between our system and a resonant tunneling in a Luttinger liquid and interpret the observed unitary resonance of vanishing width in terms of a quantum critical point (QCP). We further investigate an exotic state of electronic matter obtained by fine-tuning the system exactly to the QCP and report on several transport scaling laws both near and far from equilibrium. Particularly striking is a quasi-linear non-Fermi liquid scattering rate found at the QCP, interpreted in terms of a model with Majorana modes at the resonant level. Although unlikely to be practical for fault-tolerant quantum computing, our device constitutes a viable alternative to topological superconductors as a platform for studying strong correlation effects within Majorana physics. [Preview Abstract] |
Friday, March 22, 2013 9:48AM - 10:24AM |
Y1.00004: Nonequilibrium Kondo model: Real-time RG study of crossover from weak to strong coupling Invited Speaker: Mikhail Pletyukhov We analyze the nonequilibrium Kondo model at finite voltage and temperature by using a new formulation [1] of the real-time renormalization group [2] with the Laplace variable as the flow parameter. We evaluate the energy-dependent spin relaxation rate and nonlinear conductance, and derive an approximate form for the universal line shape for the latter in the whole crossover regime from weak to strong coupling (that is, from high to low energy scales). The results are shown to agree well with exact methods and the numerical renormalization group in equilibrium, Fermi liquid theory, weak-coupling expansions, and recent experiments [3].\\[4pt] References:\\[0pt] [1] M. Pletyukhov and H. Schoeller, Phys. Rev. Lett. 108, 260601 (2012).\\[0pt] [2] H. Schoeller, Eur. Phys. J. Special Topics 168, 179 (2009); H. Schoeller and F. Reininghaus, Phys. Rev. B 80, 045117 (2009).\\[0pt] [3] A. V. Kretinin, H. Shtrikman, D. Goldhaber-Gordon, M. Hanl, A. Weichselbaum, J. von Delft, T. Costi, and D. Mahalu, Phys. Rev. B 84, 245316 (2011); A. V. Kretinin, H. Shtrikman, and D. Mahalu, Phys. Rev. B 85, 201301(R) (2012). [Preview Abstract] |
Friday, March 22, 2013 10:24AM - 11:00AM |
Y1.00005: Quantum quench of Kondo correlations in optical absorption Invited Speaker: Andreas Weichselbaum Absorption spectra of individual semiconductor quantum dots tunnel-coupled to a degenerate electron gas in the Kondo regime have recently become accessible to the experiment [1]. The absorption of a single photon leads to an abrupt change in the system Hamiltonian, which can be tailored such that it results in a quantum quench of the Kondo correlations. This is accompanied by a clear signature in the form of an Anderson orthogonality catastrophe, induced by a vanishing overlap between initial and final many-body wave functions and with power-law exponents that can be tuned by an applied magnetic field. We have modeled the experiment in terms of an Anderson impurity model undergoing an optically induced quench, and studied this \emph{Kondo exciton} in detail using both analytical methods and the Numerical Renormalization Group (NRG). Our NRG results reproduce the measured absorption line shapes very well, showing that NRG is ideally suited for the study of Kondo excitons. In summary, the experiments demonstrate that optical measurements on single artificial atoms offer new perspectives on many-body phenomena previously studied using transport spectroscopy only. \\[4pt] [1] Latta et al, Nature {\bf 474} 627 (2011). \\[0pt] [2] T{\"u}reci et al, Phys. Rev. Lett {\bf 106}, 107402 (2011). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700