Kondo Effect — Spin-Flip Scattering

A magnetic impurity in a metal causes resistance to increase logarithmically as temperature drops — a many-body effect where conduction electrons screen the impurity spin.

Exchange J/D0.15

Impurity spin SS=½

Phonon α0.020

T_min (mK)1.0

ρ(T) = ρ₀[1 − 2JS(S+1)·ln(T/D)] + αT⁵ + ρ_phonon

Left: Resistance vs temperature showing the Kondo minimum — competition between logarithmic rise (magnetic scattering) and T⁵ phonon suppression. Right: Scattering cross-section near the Kondo resonance. Kondo temperature: T_K ≈ D·exp(−1/2JS).