Interaction between phase-slip centers in superconducting indium microbridges

We have studied the electric behavior of phase-slip centers in superconducting indium microbridges of 0.9 µm thickness, 3–4 µm width, and 70–130 µm length. Our measurements were performed in the temperature range 3–10 mK below the critical temperature T_c resulting in relatively large values (about 10–20 µm) of the quasiparticle diffusion length. The temperature dependent Ginzburg-Landau coherence length (T) has been determined for all samples from the measured temperature dependence of the critical current density. The fabrication of two notches in the indium bridge has been found to localize reliably the nucleation site of the first two phase-slip centers. Our measurements quantitatively confirmed the dc interaction predicted by the model of Kadin, Smith, and Skocpol. In addition, for temperatures very close toT_c, an ac interaction has been observed which disappears abruptly for decreasing temperature. No voltage coupling has been detected.