Charge-4e and Charge-6e Flux Quantization and Higher Charge Superconductivity in Kagome Superconductor Ring Devices

The flux quantization is a key indication of electron pairing in superconductors. For example, the wellknown h=2e flux quantization is considered strong evidence for the existence of charge-2e, two-electron Cooper pairs. Here we report evidence for multicharge flux quantization in mesoscopic ring devices fabricated using the transition-metal kagome superconductor CsV3Sb5. We perform systematic magnetotransport measurements and observe unprecedented quantization of magnetic flux in units of h=4e and h=6e in magnetoresistance oscillations. Specifically, at low temperatures, magnetoresistance oscillations with period h=2e are detected, as expected from the flux quantization for charge-2e superconductivity. We find that the h=2e oscillations are suppressed and replaced by resistance oscillations with h=4e periodicity when the temperature is increased. Increasing the temperature further suppresses the h=4e oscillations, and robust resistance oscillations with h=6e periodicity emerge as evidence for charge-6e flux quantization. Our observations provide the first experimental evidence for the existence of multicharge flux quanta and emergent quantum matter exhibiting higher-charge superconductivity in the strongly fluctuating region above the charge-2e Cooper pair condensate, revealing new insights into the intertwined and vestigial electronic order in kagome superconductors.