Voltage-Induced Rearrangements in Atomic-Size Contacts

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Atomic contacts exhibit voltage-induced conductance changes.
• Understanding these changes is crucial for nanoscale electronic devices.

Purpose of the Study:

• To investigate voltage-induced conductance changes in Pb, Au, Al, and Cu atomic contacts.
• To determine the material dependence of switching voltages and currents.
• To theoretically model the underlying mechanism driving atomic rearrangements.

Main Methods:

• Experiments using mechanically controllable break junctions in vacuum at low temperatures.
• Determination of switching histograms (voltage and current distributions) versus conductance.
• Theoretical modeling using density functional theory and a generalized Langevin equation.

Main Results:

• Observed clear material dependence in switching voltages.
• Gold (Au) showed high, conductance-independent switching voltage; Aluminum (Al) showed low, conductance-dependent switching voltage.
• Identified a 'runaway voltage' from theoretical calculations where phonon pumping destabilizes atomic arrangements.

Conclusions:

• Phonon pumping is a relevant mechanism explaining voltage-induced rearrangements in atomic contacts.
• Theoretical 'runaway voltage' qualitatively agrees with experimental switching voltages.
• Material properties significantly influence the behavior of atomic contacts under voltage stress.