Quantum Dots: a Doorway to Nanoscale Physics ppt

[...]... 172 A Guide for the Reader Quantum dots, often denoted artificial atoms, are the exquisite tools by which quantum behavior can be probed on a scale appreciably larger than the atomic scale, that is, on the nanometer scale In this way, the physics of the devices is closer to classical physics than that of atomic physics but they are still sufficiently small to clearly exhibit quantum phenomena The present... forty years ago The Andreev reflection at a superconductor modifies the excitation spectrum of a quantum dot The difference between a chaotic and integrable billiard (quantum dot) is discussed and relevant classical versus quantum time scales are given The results are a challenge to experimental physicists as they are not confirmed as yet The Renormalization Group Approach – From Fermi Liquids to Quantum. .. 113-0033, Japan NTT Basic Research Laboratories, Atsugi-shi, Kanagawa 243-0129, Japan The spin of an electron placed in a magnetic field provides a natural twolevel system suitable as a qubit in a quantum computer [1] In this work, we describe the experimental steps we have taken towards using a single electron spin, trapped in a semiconductor quantum dot, as such a spin qubit [2] The outline is as follows... off, causing the BCS instability This is the reason the V ’s are not a part of Landau theory, which assumes we have no phase transitions This is also a nice illustration of what was stated earlier: one could begin with a large positive coupling, say v3 and a tiny negative coupling v5 After much renormalization, v3 would shrink to a tiny value and v5 would dominate 10 R Shankar 3 Large-N Approach to. .. devoted to some of these fascinating aspects In the first contribution general theoretical aspects of Fermi liquids are addressed, in particular, the renormalization group approach The choice of appropriate variables as a result of averaging over “unimportant” variables is presented This is then aptly applied to large quantum dots The all important scales, ballistic dots and chaotic motion are discussed... lectures are based on a collaborative effort of research groups in the Netherlands and in Japan The last two contributions are again theoretical in nature and address particular aspects relating to quantum dots In the third lecture series, mechanisms of low-temperature electronic transport through a quantum dot – weakly coupled to two conducting leads – are reviewed In this case transport is dominated by... enters at a subdominant level inside the action, which makes it hard to predict the exact shape of the critical fan The bottom line is that we can see the critical point at finite 1/g In addition one can also raise temperature or bias voltage to see the critical fan Subsequent work has shown, in more familiar examples that Landau interactions, that the general picture depicted here is true in the large... 0, as are negative initial values as long as um (t = 0) ≥ u∗ = ˜ m −1/ ln 2 Thus, the Fermi liquid parameters are irrelevant for this range of starting values Recall that setting all um = 0 for m = 0 results in the Universal Hamiltonian Thus, the range um ≥ u∗ is the basin of attraction m of the Universal Hamiltonian On the other hand, for um (t = 0) ≤ u∗ results m in a runaway flow towards large negative... a new phase (in contrast to transitions wherein temperature T is the control parameter) Figure 6 shows what happens in a generic situation On the x-axis a variable (um in our case) along which the quantum phase transition occurs Along y is measured a new variable, usually temperature T Let us consider that case first If we move from right to left at some value of T , we will first encounter physics. .. The general rule is that whenever a momentum label corresponding to an internal line in the diagram (here µ and ν) is forced to become equal to a momentum label corresponding to an external disorder label (here α, β, γ, or δ), the diagram is down by 1/g, exactly as in the 1/N expansion The fact that 1/g plays the role of 1/N was first realized by Murthy and Shankar [24] Not only did this mean that the . 172 A Guide for the Reader Quantum dots, often denoted artificial atoms, are the exquisite tools by which quantum behavior can be probed on a scale appr eciably larger than the atomic scale, that. (Ed.) Quantum Dots: a Doorway to Nanoscale Physics 123 Editor W. Dieter Heiss University of Stellenbosch Department of Physics MATIELAND 7602 South Africa W. Dieter Heiss (Ed.), Quantum Dots: a Doorway. Tarucha ERATO Mesoscopic Correlation Project, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan NTT Basic Research Laboratories, Atsugi-shi, Kanagawa 243-0129, Japan L.M.K. Vandersypen Kavli