Thermal enhancement of interference effects in quantum point contacts

Area of Science:

• Condensed Matter Physics
• Quantum Electronics
• Mesoscopic Physics

Background:

• Electron interferometers utilize quantum point contacts and scanning probe tips.
• Conductance measurements reveal interference fringes spaced by the Fermi wavelength in 2D electron gas.

Purpose of the Study:

• Investigate fringe behavior in electron interferometers with quantized conductance.
• Explain the unusual enhancement of interference fringes at elevated temperatures.

Main Methods:

• Fabrication of an electron interferometer using a quantum point contact and scanning probe tip.
• Measurement of conductance as a function of tip position in a 2D electron gas.
• Analysis of fringe spacing and temperature dependence.

Main Results:

• Observed fringes with spacing equal to half the Fermi wavelength.
• Found fringe enhancement with increasing temperature T for contacts at quantized conductance plateau edges.
• Demonstrated fringe persistence beyond the thermal length l(T).

Conclusions:

• The study explains the unusual temperature-dependent fringe enhancement.
• A simplified model attributes the effect to a contribution vanishing at T→0 with a T-independent decay scale.