synack

First video of LK-99 Full Levitation, aka flux-pinning This video was just posted to the Chinese video-sharing site BiliBili and claims to be a highly pure synthesized sample of LK-99. What is the physical phenomenon behind this and what does it mean? Levitation of superconducting materials is a phenomenon unique to what is called Type-II superconductors, and is an effect whereby magnetic field lines becomes 'trapped' as it passes through the material, providing the force needed to levitate. These are the popular images and videos of cryogenically-cooled discs floating above a magnet frequently seen online and in the pinned post on my profile. You can think of this like strands of hair being caught in gum - the gum is suspended in mid-air by adhering strongly to the hair as the hair passes through it. The hair in this case is magnetic field lines and the gum is the Type-II superconductor. Just like hair comes in individual strands, or in other words hair is 'quantized' or 'discrete', so is the flux trapped at the 'pinning centers' quantized in what are called 'magnetic vortices' - the quantization of pinned flux lines is a key property and distinguishing characteristic of Type-II superconductors (although technically can occur in Type-I superconductors if the material thickness is smaller than the London penetration depth, which is indeed very small - specifics for the physics nerds out there). Flux-pinning is entirely unique to superconductors and is also wholly distinct from the Meissner effect. It is not a property of diamagnets or diamagnetism. At @TRIUMFLab I contributed to flux-pinning studies in Niobium crystal superconducting radio-frequency cavities used for particle acceleration. In that application, trapped flux poses an issue by increasing the remnant surface resistivity of the cavity, which has the effect of decreasing its effective quality factor or Q-factor, which is a measurement of a resonators efficiency. SRF cavities typically have Q-factors of 10E10 and trapped flux at pinning centers reduces the maximum effective accelerating electric field used to drive charged particle bunches close to the speed of light. Flux pinning is thought to arise in some Type-II superconductors by small imperfections in the crystal, also called volume defects, that enable flux to penetrate the material. In SRF cavities an issue that arises is any magnetic field that is passing through the material, e.g. by the Earth's background field, can become pinned or trapped inside the cavity as it transitions into a superconducting state. See some attached plots in the comments from a study showing how the surface resistivity of SRF cavities increases the more there is a background field as the cavity transitions into superconducting state. This is the first video I am aware of that claims to show the flux-pinned levitation of a LK-99 sample. If this is in fact what is happening, then it is a very unique and promising finding of this new materials properties and potential for future study. If this is real then it is truly ground-breaking

Three more replications of diamagnetism in LK-99 A re-cap of who they are and where to find them: @andrewmccalip working out of the @VardaSpace laboratories has replicated the apparent diamagnetic properties of LK-99 in the video attached. He did so following the recipe originally published by the Korean team using tools like a blowtorch and oven. Here you can see a fuller clip he has uploaded to youtube and also posted to his twitter / X account: youtube.com/watch?v=K7jk7r-t…… @szacilow in Poland has also claimed replication of diamagnetic properties although a write-up is forthcoming, see photo in the comments. A team of Hao Wu, Li Yang, Bichen Xiao, Haixin Chang at the Huazhong University of Science and Technology have claimed successful replication of diamagnetism in a sample of LK-99 with a more extended write-up which is available on arxiv: arxiv.org/abs/2308.01516, with photos attached in comments below. This comes in addition to the first reported replication of diamagnetism which to the best of my knowledge belongs to @iris_IGB , in addition to now several others at Chinese research universities. ~~~~~~~~ An emerging interpretation of this physical phenomenon of partial levitation is that the superconducting pathways inside the material are one-dimensional, and so do not fully support levitation in all three dimensions. Normally in a Type-II superconductor current can flow and be conducted internally in different directions however the magnetic field might induce it, as well as trap or pin magnetic flux lines internally, thus the Meissner effect might be considered the combination of several phenomenon and properties at once. Notably, replications of this partial levitation / diamagnetism have been accompanied with photos of it NOT being attracted to a magnet, showing that this is not simply a magnetized flake of material. The speed and ease of replicating the diamagnetism of LK-99 is profound - normally in preparing these materials there is an extensive amount of artisinal expertise and practical know-how required to get the recipe just right. Things are definitely getting interesting here folks