Quantum Dots – Past, Present and Open Questions Yigal Meir Department of Physics & The Ilse Katz Center for Meso- and Nano-scale Science and Technology Beer Sheva, ISRAEL
Quantum dot – an artificial device, small enough so that quantization of energy levels and electron charge are important
vertical quantum dots Single molecules
Tarucha et al.
VgVg LL RR Transmission resonance when
Example: 2d harmonic oscillator
Coulomb Blockade charging of a capacitor
Coulomb blockade peaks Single electron transistor Kastner et al.
Now include quantum effects: energies wavefunctions The peak amplitude depends on the wavefunction the electron tunnels into
n=1 n=0 Example - Quantum Hall effect: All states within a landau level are degenerate, except edge states, E n =(n+1/2)h c The radii are quantized r 2 =n 0 (n – Landau level index)
McEuen et al.
Spin flips Kouwenhoven et al.
Level statistics and random matrix theory
Artificial molecules Dynamics
RR LL Probes the excited states Nonlinear transport
Foxman et al.
Correlation between excited state of N electrons and the ground states of N+1 electrons Marcus et al.
B
Is transport through a quantum dot coherent ? Yacoby, Heiblum
Checking quantum measurement theory Aleiner, Wingreen, Meir
Buks et al.
The Kondo effect
Relevant to transport through quantum dots Ng and Lee Glazman and Raikh
chemical potential Conductance (2e 2 /h)
Goldhaber-Gordon, Kastner (1998) Cronenwett et al. (1998)
Kouwenhoven et al.
Temperature [K] Kondo scaling Goldhaber-Gordon et al.
The Kondo effect out of equilibrium Meir, Wingreen, Lee
The two-impurity Anderson model Georges & Meir chang
Kondo vs. RKKY Marcus et al.
The two-channel Kondo effect Non- Fermi liquid ground state
Oreg & Goldhaber-Gordon
More open questions Phase of transmission amplitude Heiblum
eV= E Inelastic process ? Ensslin
Noise measurements and electron bunching Heiblum
Thomas et al. (1996,1998,2000) The “0.7 anomaly”
Rejec and Meir
conclusions Quantum dots are controllable miniaturized devices, which can be instrumental in our understanding of mesoscopic and strongly correlated systems. May be the basic ingredient in applications of quantum computing. In spite of their apparent simplicity, still many open questions.
P. A. LeeP. NordlanderM. Kastner N. S. WingreenM. PustilnikU. Meirav J. KinaretA. GolubP. McEuen B. L. AltshulerY. AvishaiE. Foxman X.-G. WenA. AuerbachD. Goldhaber-Gordon A.-P. JauhoP. RojtL. Kouwenhoven A. L. AleinerO. Entin-WohlmanR. Ashoori E. ShopenA. AharonyM. Heiblum A. GeorgesT. AonoA. Yacoby D. C. LangrethY. DubiC. Marcus K. HiroseT. RejecK. Ensslin Y. GefenT. Ihn Theory:Experiment: