Charge-4e and charge-6e flux quantization and higher charge superconductivity in kagome superconductor ring devices

TL;DR

This study reports experimental evidence of multi-charge flux quantization, including h/4e and h/6e, in kagome superconductor ring devices, revealing higher-charge superconductivity and new quantum states.

Contribution

First experimental observation of multi-charge flux quantization in kagome superconductor devices, indicating higher-charge superconductivity beyond conventional charge-2e pairing.

Findings

Observation of h/2e flux quantization at low temperatures

Suppression of h/2e oscillations with increasing temperature

Emergence of h/6e flux quantization at higher temperatures

Abstract

The flux quantization is a key indication of electron pairing in superconductors. For example, the well-known h/2e flux quantization is considered strong evidence for the existence of the charge-2e, two-electron Cooper pairs. Here we report evidence for multi-charge flux quantization in mesoscopic ring devices fabricated using the transition-metal kagome superconductor CsV3Sb5. We perform systematic magneto-transport 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 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 multi-charge 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.