Fig. 1: Sketch of Anderson transition in an impurity band.
From: Anderson transition in stoichiometric Fe2VAl: high thermoelectric performance from impurity bands
When the number of randomly distributed impurities in a peridocally ordered crystal increases, the impurity electrons remain localised below a threshold value due to Anderson localisation. At the Anderson transition, the critical density of impurities allows for delocalisation of an infinitely narrow energy region of extended states inside the localised impurity states. The delocalised impurity band is marked by two mobility edges \({E}_{{{{{{{{{\rm{c}}}}}}}}}_{1,2}}\), which are critical energies that separate the localised from delocalised states.
