STANDARD SPIN-1 2 QUANTUM KICKED ROTOR IN THE INHOMOGENEOUS MAGNETIC-FIELD/

The problem of anti-unitary symmetry breaking in the model of a standa rd spin-1/2 quantum kicked rotor in an inhomogeneous magnetic field is examined in relation to the localization properties. It is shown that the functional form of the spin-dependent term in the kicking potenti al (not the anti-unitary symmetries) is responsible for localization l ength changes. Our numerical results for the proposed functional form yield evidence of an anomalous and continuous growth of the localizati on length with an increase in the magnitude of the magnetic field.