- Hofstadter's butterfly
Hofstadter's Butterfly refers to a
fractal discovered byDouglas Hofstadter in his paper "Energy levels andwavefunction s of Bloch electrons in rational and irrationalmagnetic field s." Hofstadter's Butterfly was the first fractal to be formulated in physics.It gives a graphical version of the spectrum of thealmost Mathieu operator for at different frequency.Written while he was at the
University of Oregon , this paper was influential in directing further research. Hofstadter predicted that the allowed energy level values of an electron in this crystal lattice, as a function of a magnetic field applied to the system, formed a fractal set. That is, the distribution of energy levels for large scale changes in the applied magnetic field repeatpattern s seen in the small scale structure. This fractal structure is generally known as "Hofstadter's butterfly", and has recently been confirmed in transport measurements in two-dimensional electron systems with a superimposed nano-fabricated lattice. [ [http://prola.aps.org/abstract/PRB/v14/i6/p2239_1 "Energy levels and wave functions of Bloch electrons in rational and irrational magnetic fields"] , Phys. Rev. B 14, 2239 (1976)] [ [http://physics.technion.ac.il/~odim/hofstadter.html The Hofstadter Butterfly] ]ee also
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