Quantum fluctuations in empty space enhance superconductivity

Summary

USTC researchers have demonstrated for the first time that quantum vacuum fluctuations engineered in a dark cavity within the terahertz range can enhance superconductivity in NbSe2. This method raises the critical temperature by up to 5.4% without any external energy input.

Why it matters

This provides the first experimental evidence that the quantum vacuum can be treated not as a passive background, but as an active control knob. This opens a new pathway for tuning the quantum states of matter without physical contact. If the effect can be scaled, it could offer a fundamental approach for designing superconductors and other quantum materials without direct electrical or optical driving.

Highlights

• A 5.4% increase in critical temperature in six-layer NbSe2; critical current and critical field also strengthened in the region near the transition point
• A terahertz split-ring resonator (dark cavity) reshapes the electromagnetic environment, amplifying vacuum fluctuations that are otherwise negligible
• A resonance-like amplification peak dependent on the cavity's photonic frequency; ruling out explanations based on strain, disorder, or metallic screening

Critical take

While a 5.4% shift in critical temperature in a single, carefully tuned NbSe2/cavity geometry serves as a convincing proof of concept, it remains a modest practical gain. The paper provides no evidence that this effect can be transferred to high-temperature or bulk superconductors. Furthermore, the strong dependence of the effect on a specific dark cavity resonance leaves a significant question mark regarding its broad applicability.