Superconducting phase with fractional vortices in the frustrated kagome wire network at f=1/2 - art. no. 134522

In classical XY kagome antiferromagnets, there can be a low-temperature pha se where (3) = e(i3 theta) has quasi-long-range order but psi is disordered , as well as more conventional antiferromagnetic phases where psi is ordere d in various possible patterns (theta is the angle of orientation of the sp in). To investigate when these phases exist in a physical system. we study superconducting kagome wire networks in a transverse magnetic field when th e magnetic flux through an elementary triangle is a half of a flux quantum. Within Ginzburg-Landau theory, we calculate the helicity moduli of each ph ase to estimate the Kosterlitz-Thouless (KT) transition temperatures. Then at the KT temperatures, we estimate the barriers to move vortices and the e ffects that lift the large degeneracy in the possible psi patterns, The eff ects we have considered are inductive couplings, nonzero wire width, and th e order-by-disorder effect due to thermal fluctuations. The first two effec ts prefer q = 0 patterns, while the last one selects a root3 x root3 patter n of supercurrents. Using the parameters of recent experiments, we conclude that at the KT temperature, the nonzero wire width effect dominates, which stabilizes a conventional superconducting phase with a q = 0 current patte rn. However, by adjusting the experimental parameters, for example by bendi ng the wires a little, it appears that the psi (3) superconducting phase ca n instead be stabilized. The barriers to vortex motion are low enough that the system can equilibrate into this phase.