Low-Field Anomaly in 2D Hopping Magnetoresistance Caused by Spin-Orbit Term in the Energy Spectrum

We demonstrate that a k-linear spin-orbit term ^HSO in the Hamiltonian of a 2D electron, causing a minimum in the energy spectrum at finite k=k₀, changes the low-field dependence of magnetoresistance from δR(B)∝-|B| to δR(B)∝-1/2(|B-B₀|+|B+B₀|-2B₀), where B₀=k₀²Φ₀π is an effective field generated by ^HSO. The anomaly is suppressed by orienting electron spins in the plane with a strong parallel magnetic field.