XXXIV International School on the Physics of Semiconducting ...

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EF2DEG propertiesFree electrons in 2D with a reduced mass2 2kF1= = m v*2m2 ** 2F= 0.067meLow (tunable) electron density and long Fermi wavelength2π2π11 2λ = = 39nm n = = 4.2×10 / cmFk FHigh mobility and long elastic mean free pathµ = 1.0 x 10 6 cm 2 */V s = vmµ e=11µmλF2FmGood review article for basics about 2DEG and quantum point contactsBeenakker and van Houten, Solid State Physics 44 1 (1991) (cond-mat/0412664)
Page 1: Imaging Coherent Electron FlowBrian
Page 5: Two-dimensional electron gasQuantum
Page 9 and 10: EF+ δµJn = e ∫ ρn( E)vndEEFCur
Page 11 and 12: Quantum point contacts-modesConduct
Page 13 and 14: Quantum point contact-energy levels
Page 15 and 16: Liquid helium temperature scanningp
Page 17 and 18: Liquid helium temperature scanning
Page 19 and 20: Weak ScattererImaging mechanismNo B
Page 21 and 22: Electrostatic simulationn ⎛sV ⎞
Page 23 and 24: Importance of depletion regionV tip
Page 25 and 26: Outline• Introduction• Measurem
Page 27 and 28: Coherent fringesConstructive & Dest
Page 29 and 30: Heating electronsSmall Bias Voltage
Page 31 and 32: Modal summaryExperimentTheory1st Mo
Page 33 and 34: Electron-wave flow through 2DEG“I
Page 35 and 36: Modal patterns far away from QPC1st
Page 37 and 38: Unexpectedly high resolution100nmTi
Page 39 and 40: Quantum and classical simulations0.
Page 41 and 42: QPC Location shifts by 20 nmMoving
Page 43 and 44: Mapping 2DEG potentialTip Locations
Page 45 and 46: Outline• Introduction• Measurem
Page 47 and 48: Coherent fringesConstructive & Dest
Page 49 and 50: Thermal smearing (continued)Now sup
Page 51 and 52: Fringe persistence1D model of fring
Page 53 and 54: Backscattering from Tip and Impurit
Page 55 and 56: Fringe persistence far from the QPC
Page 57 and 58:
ReflectorVoltageFringe strength ana
Page 59 and 60:
Single BounceFringe movementDouble
Page 61 and 62:
Heating electrons1.7KQPC GatesRefle
Page 63 and 64:
Interference fringesSpaced by half
Page 65 and 66:
Therefore want a local probe of den
Page 67 and 68:
Changing Fermi energyEffect of redu
Page 69 and 70:
Measuring local electron densityDen
Page 71 and 72:
Mapping electron density∆G(e 2 /h
Page 73 and 74:
Outline• Introduction• Measurem
Page 75 and 76:
Electron optics theoryAnalog to Opt
Page 77 and 78:
Electron optics element - ballBall
Page 79 and 80:
Electron opticsImaged electrons tra
Page 81 and 82:
InteractionsTo design devices relyi
Page 83 and 84:
Voltage applied across QPC0.0 meV A
Page 85 and 86:
Measuring electron energyFringe spa
Page 87 and 88:
Differential conductance vs. excess
Page 89 and 90:
Signal Vs. excess energySignal deca
Page 91 and 92:
ExperimentAcknowledgementsHarvard U
Page 93 and 94:
Current workCombined scanning tunne
Page 95:
Imaging with AC voltage on tipTip V
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