XXXIV International School on the Physics of Semiconducting ...

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Experimental techniqueAFM CantileverQuantum PointContact (QPC) GateTwo-dimensionalElectron Gas (2DEG)GaAs/AlGaAsheterostructuren-type GaAssubstratePerturbation from tip causes scatteringwhich changes the conductance of the QPCImage obtained by measuring conductancethrough the QPC as a function of tip positionHigh flow High scattering High signalNo flow No scattering No signal
Weak ScattererImaging mechanismNo Backscattering=Conductance UnchangedStrong ScattererBackscattering=Conductance Reduced
Page 1: Imaging Coherent Electron FlowBrian
Page 5 and 6: Two-dimensional electron gasQuantum
Page 8 and 9: Quantum point contactsElectrons flo
Page 10 and 11: Quantum point contacts-quantization
Page 12 and 13: Quantum point contact-energy levels
Page 14 and 15: Outline• Introduction• Measurem
Page 16 and 17: Liquid helium temperature scanning
Page 20 and 21: Effect of tip height10 nm 15 nm 20
Page 22 and 23: Quantum mechanical simulationGatesT
Page 24 and 25: Imaging requirementsPerturbation fr
Page 26 and 27: Topinka, LeRoy et al., Science 289,
Page 28 and 29: Opening QPCNew Modes of current onl
Page 30 and 31: Extracting a modal patternExperimen
Page 32 and 33: Selective mode suppressionNo TipTip
Page 34 and 35: Coherent electron flow through a 2D
Page 36 and 37: Simulated imageDoes the presence of
Page 38 and 39: Unperturbed Currentand Tip Perturba
Page 40 and 41: Formation of CausticsClassical Traj
Page 42 and 43: Shifting QPCUnequal voltage on QPC
Page 44 and 45: Imaging a QPCImaged electron flow n
Page 46 and 47: Interference fringesPresence of int
Page 48 and 49: Finite temperature- thermal smearin
Page 50 and 51: Thermal smearing (continued)As the
Page 52 and 53: Fringe persistenceFringe Size (%)Di
Page 54 and 55: Fringe persistence far from the QPC
Page 56 and 57: Scattering induced fringe enhanceme
Page 58 and 59: Single BounceFringe movementDouble
Page 60 and 61: Fringe amplitudeFringes enhancedRef
Page 62 and 63: Temperature dependenceIncreased tem
Page 64 and 65: Outline• Introduction• Measurem
Page 66 and 67: Electron densityFree electrons in t
Page 68 and 69:
Effect of reducing Fermi energyBack
Page 70 and 71:
Is it really local?Calculate spacin
Page 72 and 73:
Electron densityInterference fringe
Page 74 and 75:
Electron opticsCreate elements to e
Page 76 and 77:
Electron optics element - prism1µm
Page 78 and 79:
Electron optics element - channel
Page 80 and 81:
Outline• Introduction• Measurem
Page 82 and 83:
DC bias techniqueNo Energy LossCond
Page 84 and 85:
Images of electron flow2.74 µm fro
Page 86 and 87:
Measuring e-e scattering lengthElec
Page 88 and 89:
Differential conductance vs. excess
Page 90 and 91:
InteractionsImages are sensitive to
Page 92 and 93:
Image pattern of electronflow from
Page 94 and 95:
Improved fringe resolutionWiggling
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XXXIV International School on the Physics of Semiconducting ...

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