Gauge field, Aharonov-Bohm flux, and high-Tcsuperconductivity

In a spin-1/2 Heisenberg model with short-range antiferromagnetic order, a hole making a closed loop on one sublattice is subject to a slowly varying spin-quantization axis and picks up a phase equal to half the solid angle subtended by the spin orientation around the loop. The phase can be represented by an Aharonov-Bohm flux resulting in a U(1) gauge theory. For a finite hole density this model leads to superconductivity even in the presence of Coulomb repulsion. The gauge field also enhances low-energy particle-hole excitations, leading to a $T^{4/3}$ law for the normal-state resitivity.