paper

Search for magnetic field expulsion in optically driven K $_{3}$ C $_{60}$

arXiv:2502.20276

Abstract

Photoexcited K $_{3}$ C $_{60}$ displays several properties reminiscent of equilibrium superconductivity, including transient optical spectra, pressure dependence, and I-V characteristics. However, these observations do not decisively establish non-equilibrium superconductivity, which would be conclusively evidenced by transient Meissner diamagnetism, as shown recently in driven YBa $_{2}$ Cu $_{3}$ O $_{6.48}$ . Here, we search for transient magnetic field expulsion in K $_{3}$ C $_{60}$ by measuring Faraday rotation in a magneto-optic material placed in its vicinity. Unlike in the case of homogeneous, insulating YBa $_{2}$ Cu $_{3}$ O $_{6.48}$ , inhomogeneous, metallic K $_{3}$ C $_{60}$ powders reduce the size of the effect. With the $\sim 50$ nT magnetic field resolution achieved in our experiments, we provide an upper limit for the photo-induced diamagnetic volume susceptibility ( $I ¨ _{v} > - 0.1$ ). On this basis, we conclude that the photo-induced phase has weaker diamagnetism than superconducting K $_{3}$ C $_{60}$ at zero temperature. Yet, from recent nonlinear transport measurements in this granular material, we expect a light-induced state similar to the equilibrium superconductor near 0.8 T $_{c}$ , for which $I ¨ _{v} > - 0.1$ . A definitive conclusion on the presence or absence of Meissner diamagnetism cannot be made for K $_{3}$ C $_{60}$ with the current resolution.

3 figures, 42 pages, including supplementary information. arXiv admin note: text overlap with arXiv:2408.05153

Search for magnetic field expulsion in optically driven K3​C60​

Abstract

Search for magnetic field expulsion in optically driven K $_{3}$ C $_{60}$