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

Jun Ge, Pinyuan Wang+7 more|arXiv (Cornell University)|Jan 25, 2022

Physics of Superconductivity and Magnetism35 references22 citations

TL;DR

The paper reports magneto-transport evidence for multi-charge flux quantization (h/2e, h/4e, h/6e) in CsV3Sb5 kagome superconductor rings, indicating higher-charge superconductivity.

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.

Motivation & Objective

• Motivate flux quantization as a signature of electron pairing and explore multi-charge states in kagome superconductors.
• Demonstrate higher-charge superconductivity (beyond charge-2e) in mesoscopic ring devices.
• Identify conditions under which h/4e and h/6e flux quanta emerge in CsV3Sb5.
• Characterize the temperature dependence of flux-quantized oscillations and associated electronic order.

Proposed method

• Fabricate mesoscopic ring devices from the kagome superconductor CsV3Sb5.
• Perform systematic magneto-transport measurements to detect magnetoresistance oscillations.
• Analyze oscillation periods to identify flux quanta corresponding to h/2e, h/4e, and h/6e.
• Study temperature dependence to observe suppression and emergence of different charge quanta.
• Interpret results as evidence for multi-charge flux quantization and higher-charge superconductivity.

Experimental results

Research questions

• RQ1 Do kagome superconductors support flux quantization beyond h/2e in mesoscopic rings?
• RQ2 Under what conditions do h/4e and h/6e oscillations appear in CsV3Sb5 rings?
• RQ3 How does temperature influence the observed flux quanta and related electronic order?

Key findings

• At low temperatures, magnetoresistance oscillations with period h/2e are observed.
• As temperature increases, h/2e oscillations are suppressed and h/4e oscillations become dominant.
• With further temperature increase, robust oscillations with h/6e periodicity emerge.
• The results provide the first experimental evidence for multi-charge flux quanta and higher-charge superconductivity in a kagome superconductor.
• The study reveals insights into intertwined and vestigial electronic order in CsV3Sb5.