Question

I have a question regarding the smearing of conductance plateaus of quantum point contacts (QPC). Conductance plateaus smear if the system is at a finite temperature T>0 K. What is the exact mechanism behind it? Does the transmission behavior of the charge carriers change with temperature? Can the plateaus also become smeared when a small source drain ac bias is applied, since the charge carriers receive additional energy from the bias?

Answer 1

Conductance plateaus in quantum point contacts (QPC) smear at finite temperature due to the change in transmission behavior of charge carriers. Applying a small source-drain AC bias can also lead to smear plateaus.

Step-by-step explanation:

Exactly how conductance plateaus smear at finite temperature

The smearing of conductance plateaus in quantum point contacts (QPC) at finite temperature T>0 K is mainly due to the change in transmission behavior of the charge carriers with temperature. At higher temperatures, the thermal energy of the charge carriers increases, which causes them to have more kinetic energy and a larger spread in their momenta. This leads to a broader range of energy states being available for the charge carriers to occupy, resulting in a smearing of the conductance plateaus.

The effect of small source-drain AC bias on plateaus smearing

Applying a small source-drain AC bias to a QPC can also result in the smearing of conductance plateaus. The additional energy provided by the bias can excite the charge carriers and increase their thermal energy, similar to the effect of temperature. This can lead to a broadening of the energy distribution and a smearing of the plateaus.