noise in corbino disk: Anisotropic mobility fluctuations?

Suppression of $1/f$ noise in graphene due to non-scalar mobility fluctuations induced by impurity motion

“…When there is full positive (scalar) correlation (χ = 1), the noise vanishes at µ 0 B = 1. With full negative correlation χ = −1, no suppression is seen in the studies for changes in resistance due to reorganization of atoms 39,40,26 and also with noise correlation measurements in semimetallic Bi 41 . According to our own kinetic Monte Carlo simulations (see Methods), the correlation coefficient is χ ≃ −0.7 and −0.4 for k B T E d = 0.3 and at k B T E d = 0.5, respectively; here E d is the energy barrier for hopping between sites.…”

“…For Corbino devices with isotropic (scalar) mobility fluctuations δµ 0 , the current fluctuations should vanish at a sweet spot having µ 0 B = 1. In practice, the sweet spot does not reduce the noise down to zero, but non-idealities/other noise sources will limit the reduction [23][24][25][26][27] . On the other hand, partial correlations between mobility fluctuations in radial δµ r and azimuthal δµ ϕ direction may account for the observed noise reduction.…”

“…This feature means that, if there are isotropic mobility fluctuations (fully correlated in two orthogonal directions) causing 1 f noise, this noise component will be suppressed to zero at µ 0 B = 1 22 ; here µ 0 denotes the mobility at B = 0. This behavior has unsuccessfully been searched for both in two-dimensional electron gas [23][24][25][26] as well as in graphene 27 . Our experimental results display a clear suppression of noise as a function of B, with a minimum around µ 0 B ≃ 1.…”

“…f noise[23][24][25][26][27] . By taking into account s m ∝ 1 1 + (µ 0 B) 2 , our results in Fig.3a yieldχ ≃ −0.5 ± 0.1 away from the Dirac point.…”