MPLSUSTech
中文

Physics primers

If you are new to mesoscopic physics, start with three questions. How small is the device? What do its electrodes measure? Which physical effects can you identify in those signals? Read in order or go directly to a concept in the paper you are studying.

  1. How small is mesoscopic?

    The same small metal ring can show a different resistance trace when it is cooled and a magnetic field is swept. Its diameter stays fixed. What can change is the distance over which electrons retain phase information.

  2. Four-terminal transport: why use four wires?

    Two contacts carry current into and out of a sample. A separate pair measures the voltage between two points along it. This selects the part of the sample of interest and greatly reduces the contribution from the current leads and contacts.

  3. The Hall effect and quantized plateaus

    Send a current along a narrow sample and connect a voltmeter across its width. Why does a perpendicular magnetic field produce a voltage there? And why, in some samples, does that voltage stay constant over a range of fields?

  4. Detecting superconductivity in a thin crystal

    Cool a crystal and its resistance may drop sharply over a small temperature interval. To interpret the drop, it helps to know how resistance is measured, which point defines the transition temperature, and what a magnetic measurement can tell us.

  5. Photocurrent: what changes when the light turns on?

    Hold the voltage across a device fixed and switch the light on and off. The change in current is the photocurrent. To find out what produced it, compare measurements at different wavelengths, biases or optical powers.