Researchers from the High Magnetic Field Laboratory at the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, in collaboration with Nanjing University and Yanshan University, have directly observed the Meissner effect in two-dimensional (2D) superconductors using a high-sensitivity magnetic measurement technique.
Their findings have been published in Advanced Materials.
Two-dimensional van der Waals superconductors have emerged as a frontier in condensed matter physics due to their rich low-dimensional quantum phenomena and unconventional properties. However, their extremely small volume and ultralow magnetic signals have made it challenging to directly observe the Meissner effect, one of the two fundamental hallmarks of superconductivity. As a result, superconductivity in these systems has long been inferred primarily from zero-resistance transport measurements, limiting a comprehensive understanding of their intrinsic properties.
In this study, the research team developed a high-sensitivity magnetic measurement method and theoretical framework tailored for anisotropic superconducting systems. This approach is based on a compact dynamic cantilever magnetometry technique previously developed by the team. It enables the quantitative extraction of key physical quantities, including magnetization, magnetic susceptibility, and diamagnetic screening efficiency.
The method is much more sensitive than conventional approaches for detecting magnetic signals. It achieves a magnetic moment sensitivity of approximately 1.1×10-17 A·m2@1T and an AC susceptibility sensitivity of 9.4×10-17 A·m2/T@1T, exceeding the detection limits of existing techniques.
Using 2M-WS2, a specific structural phase of layered tungsten disulfide, as a model system, the researchers observed clear magnetic hysteresis loops for the first time in microscale, hundred-nanometer-thick 2D superconducting samples, directly revealing the characteristic behavior of type-II superconductors. In addition, in ultrathin samples down to 4 nm thickness, they achieved precise measurements of magnetic susceptibility and diamagnetic screening efficiency, providing direct experimental evidence of the Meissner effect in 2D superconductors.
This work addresses a key challenge in detecting magnetic signatures of superconductivity in low-dimensional systems and provides a general platform for high-sensitivity magnetic characterization, according to the team.
Ultrasensitive detection of the Meissner effect in two-dimensional superconductors (Image by WANG Kang)
