Scaling theory of electric-field-assisted tunnelling

Source abstract

Recent experiments report the current ( I ) versus voltage ( V ) characteristics of a tunnel junction consisting of a metallic tip placed at a distance d from a planar electrode, d varying over six orders of magnitude, from few nanometres to few millimetres. In the ‘electric-field-assisted’ (or ‘field emission’) regime, as opposed to the direct tunnelling regime used in conventional scanning tunnelling microscopy, all I – V curves are found to collapse onto one single graph when d is suitably rescaled, suggesting that the current I = I ( V , d ) is in reality a generalized homogeneous function of one single variable, i.e. I = I ( V ⋅ d − λ ) , where λ being some characteristic exponent and I ( x ) being a scaling function. In this paper, we provide a comprehensive explanation—based on analytical arguments, numerical simulations and further experimental results—for the scaling behaviour that we show to emerge for a variety of tip–plane geometries and thus seems to be a general feature of electric-field-assisted tunnelling.