Low-frequency noise in quantum point contacts

The kinetics of electron transport in quantum point contacts has been studied by means of low-frequency noise spectroscopy. The temperature and frequency (Lorentzian of 1/f) dependences of the noise intensity are found to be device specific, in contrast to the conductance dependence, which universally exhibits a strong quantum size effect at low temperatures. The origin of the Lorentzian noise spectrum is electron trapping and release at a single trap close to the point contact, and is connected to random resistance switching in the time domain. The 1/f noise in other point contacts is attributed to a collection of traps in the vicinity of the point contact. A comprehensive model is presented which accounts for the conductance and temperature dependences of the noise in quantum point contacts.