Someone says The fractional quantum Hall effect is an incompressible quantum liquid, what's the meaning?
"Incompressible" refers to the property of a material or system to resist changes in its density or volume. In the context of FQHE, it describes the behavior of a quantum fluid at extremely low temperatures and high magnetic fields, where the fluid becomes highly resistant to changes in its density.
The incompressibility of a quantum fluid is a crucial factor in the fractional quantum Hall effect (FQHE). In order for the FQHE to occur, the quantum fluid must be in an incompressible state where its density remains constant even under an applied magnetic field. This allows for the formation of fractional charges and excitations, which are the hallmark of the FQHE.
Some examples of incompressible quantum fluids include electron and hole gases in semiconductors, as well as helium-3 and helium-4 at low temperatures. These materials exhibit the FQHE phenomenon when subjected to extreme conditions of low temperatures and high magnetic fields.
In FQHE experiments, the incompressibility of a quantum fluid is typically measured by observing the resistance of the fluid to changes in its density. This is done by applying a magnetic field and varying the density of the fluid, and then measuring the resulting voltage or current. A highly incompressible fluid will exhibit a plateau in its resistance, indicating the presence of the FQHE.
Yes, the incompressibility of a quantum fluid can be manipulated or controlled through various means, such as changing the temperature, pressure, or magnetic field. In addition, researchers are exploring ways to engineer materials with specific properties that could enhance the incompressibility of quantum fluids, potentially leading to new applications in quantum computing and other fields.