Observation of conductance quantization of ballistic metallic point contacts at room temperature

We show here that the room-temperature conductance of the contacts formed with an ultrahigh vacuum scanning tunneling microscope by repeatedly pressing the tip into the clean and well-ordered Au(001) sample is sometimes but certainly not always equal to integer multiples of 2(Formula presented)/h, while the frequency distribution of conductance obtained from numerous such contacts has major peaks at and only at integer multiples of 2(Formula presented)/h, thereby providing direct evidence of conductance quantization of the room temperature ballistic metallic point contacts.