Chapter 3. Differential Resistance Through a Quantum Dot
Chapter 3. Differential Resistance Through a Quantum Dot:
Signature of Kondo Correlation
Academic and Research Staff
Professor Patrick A. Lee
Graduate Students
Jari M. Kinaret, Dmitri B. Chklovskii
Technical and Support Staff
Imadiel Ariel
3.1 Project Description
SponsorJoint Services Electronics Program Contract DAAL03-92-C-0001
The behavior of an atomic impurity coupled to con-duction electrons has become one of the paradigms of condensed matter physics. Competition between on-site Coulomb interaction and band hybridization produces the Kondo effect: a crossover from weak to strong coupling between the localized and band electrons below the Kondo temperature, TK. The study of the Kondo effect has been limited, however, by the nature of the impurity system. Since it is a daunting task to drive the host metal out of equilibrium, it is the equilibrium properties of Kondo impurities that have been explored.
In the study of transport through a quantum dot, we have a new Kondo system in which
non-equilibrium--a semiconductor quantum dot weakly coupled to its leads-is routinely achieved. Anderson's model for a Kondo impurity-discrete, interacting levels coupled to a band-also describes quantum dots. The discrete spectrum of a single dot has been probed experimentally by transport and capacitance spectroscopy, and the strong on-site Coulomb interaction is observed in
1 U. Meirav, M. Kastner, and S.J. Wind, "Single-Electron Charging
Lett. 65: 771 (1990).
Coulomb-blockade conductance oscillations.' Anderson's model has provided an excellent theore-tical description of these experiments.2 However, it is only the high temperature regime that has been explored experimentally, while it is below TK that the Kondo effect emerges.
We have previously shown that below TK, the Kondo resonance leads to perfect transparency of the quantum dot at the Fermi energy. This leads to dramatic effects on the lineshape of the conduc-tance peaks as a function of gate voltage.3 We recently realized that a striking signature on the Kondo correlation appears in nonequilibrium proper-ties, such as the differential conductance, even at a temperature higher than TK.4 The requirement is that the temperature must be less than F, the intrinsic line width of the resonant transmission peak. This latter condition is much easier to realize experimentally. We have shown that if the gate voltage is set so that we are on the shoulder of a conductance peak and the source drain voltage VsD
is increased, the differential conductance would exhibit a peak around VSD=O. Furthermore, if a
magnetic field B is applied, the differential conduc-tance peak will split into two peaks centered at the Zeeman energy ± giB1B. We believe that the obser-vation of this conductance peak is a clean signature of the Kondo correlation in the quantum dot system.
and Periodic Resonances in GaAs Nanostructures," Phys. Rev. 2 Y. Meir, N. Wingreen, and P.A. Lee, "Transport Through a Strongly Interacting Electron System," Phys. Rev. Lett. 66: 3048 (1991).
3 T.K. Ng and P.A. Lee, "On-site Coulomb Repulsion and Resonant Tunnelling," Phys. Rev. Lett. 61: 1768 (1988).
4 Y. Meir, N. Wingreen, and P.A. Lee, "Low Temperature Transport Through a Quantum Dot: The Anderson Model Out of Equilibrium," submitted to Phys. Rev. Lett.
Chapter 3. Differential Resistance Through a Quantum Dot
3.2 Publications
Lee, P.A. "Few Electron Nanostructures: A New Laboratory for Studying Strongly Correlated Systems." Proceedings of NATO Workshop,
Nordwig, Netherlands, 1992.
Meir, Y., N. Wingreen, and P.A. Lee. "Low Temper-ature Transport Through a Quantum Dot: The Anderson Model Out of Equilibrium." Submitted to Phys. Rev. Lett.
