Topological effects of charge density waves in ring-shaped crystals of NbSe₃

We studied the differences of the charge density wave (CDW) dynamics in closed-ring and open-ring topologies by measuring the frequency-dependent resistance in the radio-frequency range. We performed a two-probe ac resistance measurement for a ring-shaped crystal of niobium triselenide (NbSe₃) in the 300 kHz to 1.3 GHz frequency range. We compared the frequency dependence of the resistance of closed-ring and open-ring crystals and found that the pinning potential in the former is smaller than that in the latter. The open-ring crystal was obtained by changing of the topology of the closed-ring crystal. We believe that the reduction in the pinning effect is caused by a CDW circulating current in the closed-ring topology.