Quantum Hall ferromagnets: Induced topological term and electromagnetic interactions

Article

关键词: 2-DIMENSIONAL ELECTRON-GAS;    HOPF TERM;    PHASE;    STATISTICS;    SKYRMIONS;    SOLITONS;    SPIN;   

DOI  :  10.1103/PhysRevB.60.14154

来源: SCIE

【 摘 要 】

The nu=1 quantum Hall ground state in materials such as GaAs is well known to be ferromagnetic in nature. The exchange part of the Coulomb interaction provides the necessary attractive force to align the electronic spins spontaneously. The gapless Goldstone modes are the angular deviations of the magnetization vector from its fixed ground-state orientation. Furthermore, the system is known to support electrically charged spin skyrmion configurations. It has been claimed in the literature that these skyrmions are fermionic owing to an induced topological Hopf term in the effective action governing the Goldstone modes. However, objections have been raised against the method by which this term has been obtained from the microscopics of the system. in this paper, we use the technique of the derivative expansion to derive, in an unambiguous manner, the effective action of the angular degrees of freedom, including the Hopf term. Furthermore, we have coupled perturbative electromagnetic fields to the microscopic fermionic system in order to study their effect on the spin excitations. We have obtained an elegant expression for the electromagnetic coupling of the angular variables describing these spin excitations. [S0163-1829(99)02240-7].

【 授权许可】

Free