Tunneling spectroscopy of quantum point contacts

A tunneling current flowing through a thin sidewall of quantum point contacts is calculated using a mode-matching technique. When the width of the construction is varied, successive peaks in the tunneling probability, which are synchronized with the quantized steps in the point-contact current, are observed due to the one-dimensional density of states in the constriction sweeping through the Fermi level. The modulation structure depends on the side-barrier potential. A resonant structure due to multiple reflections between sharp edges at the end of the point contact is superposed on the modulation if the point contact is sufficiently long compared with the wavelength. We find that a sharp peak occurs in the tunneling probability when the Fermi level coincides with a quasi-bound-state level in the constriction.