Fabrication of highly stable configurable metal quantum point contacts

Metal quantum point contacts (MQPCs), with dimensions comparable to the de Broglie wavelength of conducting electrons, reveal ballistic transport of electrons and quantized conductance in units of G₀ = 2e ²/h. While these contacts hold great promise for applications such as coherent controlled devices and atomic switches, their realization is mainly based on the scanning tunneling microscope (STM) and mechanically controlled break junction (MCBJ), which cannot be integrated into electronic circuits. MQPCs produced by these techniques have also limited stability at room temperature. Here we report on a new method to form MQPCs with quantized conductance values in the range of 1-4G₀. The contacts appear to be stable at room temperature for hours and can be deterministically switched between conductance values, or reform in case they break, using voltage pulses. The method enables us to integrate MQPCs within nanoscale circuits to fully harness their unique advantages.