Difference: QuantizedConductance (6 vs. 7)

Revision 72018-04-12 - JinHe

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 Lab Assignment: Quantized Conductance Lab
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 Please read the references(see the three attachments at the bottom of this page) to understand the quantized conductance through classical Physics (Drude model) and Quantum Physics.

Quantum conductance can also refer to Wikipedia: https://en.wikipedia.org/wiki/Conductance_quantum
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+You can also read refs about quantum tunneling.
  Setup and calibration 

Before the experiment, you need to understand the theory and principle of the experiment.
 You will learn:
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+. How to prepare sharp gold tip and clean both gold tip and gold substrate
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+. How to prepare sharp(a few nanometer at the tip) gold tip and clean both gold tip and gold substrate
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+. How the experimental setup works.
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+. How the experimental setup works (electric circuit, noise reduction...).
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+. How to repeatedly acquire the conductance-distance data.
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+. Data acquisition using DAQ card (from national instrument) and customed labview programs
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+. Data acquisition using NI DAQ and labview programs
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+. How to repeatedly acquire a large number of the conductance-distance (I-d) curves.
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+. Statistical data analysis, build histogram, perform Gaussian fits to the histogram.
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+. Statistical data analysis, build histogram, perform Gaussian fits to the histogram.
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+. Develop understanding of quantum mechanics
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+. Develop understanding of quantum mechanics
  Part A: Data Collection 

Observe quantum steps in the current vs distance (I-d) curve. You should be able to see at least one conductance (conductance=current/voltage) step at G0=2e^2/h=77.5 microsiemen (uS) or R0=1/G0=12.9 kohm, There are typically more than 1 steps, appearing at 1G0, 2G0, 3G0...
 Collect about 200 withdraw conductance curves (more is better) at different biases, 0.05V, 0.1V, 0.2V.
 Part B: Data Analysis
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+You will use the labview programs to build histograms from your hundreds of conductance curves (conductance vs. distance). You need to understand how to covert individual conductance curves to conductance histograms. After buding conductance histograms, you will perform Gaussian fits to the conductance peaks in the histograms. You will discuss the goodness of fit using reduced chi-square.
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+You will use the labview programs to build conductance histograms from hundreds of I-d curves you collected. You need to understand how to covert the current unit Amper to quantume conductance unit G0 and how to convert individual I-d curves to G-d curves, then to a conductance histogram (pay attention to the bin size). After buding conductance histograms, you will perform Gaussian fits to the conductance peaks in the histograms. You will discuss the goodness of fit using reduced chi-square.
  Materials and Equipment: 

The list of necessary equipment is:
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+ Current amplifier for small current measurement
  Stepper motor for low precision movement of gold tip.
  Piezo driver and piezo actuator to control the high precision movement of gold tip.
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+ Current amplifier for small current measurement (understand pA, nA and uA current scales)
  Stepper motor for low precision movement of gold tip (about 100 nm resolution).
  Piezo driver and piezo actuator to control the high precision movement of gold tip (about 0.1 nm resolution).
  Data acquisition setup, labview program to control the hardware
  Electrical and Mechanical noise reduction setup
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+Write Up
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+Write Up
 You need to explain the experiment principle and theory.
 Other interesting discovers in your experiments.
 Comments
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+  (Edit - Preview)
 
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 .4765331-Quantum_step_ref1.pdf: ref 1
 
 

 Quantized_Conductance_ref_2.pdf: ref 2

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