Semiclassical analysis of edge state energies in the integer quantum Hall effect
Abstract
Analysis of edge-state energies in the integer quantum Hall effect is carried out within the semiclassical approximation. When the system is wide so that each edge can be considered separatly, this problem is equivalent to that of a one dimensional harmonic oscillator centered at x=xc and an infinite wall at x=0, and appears in numerous physical contexts. The eigenvalues En(xc) for a given quantum number n are solutions of the equation S(E,xc)=π [n+ γ(E,xc)] where S is the WKB action and 0<γ<1 encodes all the information on the connection procedure at the turning points. A careful implication of the WKB connection formulae results in an excellent approximation to the exact energy eigenvalues. The dependence of γ [En(xc),xc] γc (xc) on xc is analyzed between its two extreme values 1/2 as xc goes to -infinity far inside the sample and 3/4 as xc goes to infinity far outside the sample. The edge-state energies En(xc) obey an almost exact scaling law of the form En(xc)=4 [n+γn(xc)] f(xc/4 n +3) and the scaling function f(y) is explicitly elucidated