Amazing stuff! When will superconductivity finally become more practical and usable!
"... For about 15 years, Kagome materials with their star-shaped structure reminiscent of a Japanese basketry pattern have captivated global researchers. Only since 2018, have scientists been able to synthesize metallic compounds featuring this structure in the lab.
Thanks to their unique crystal geometry, Kagome metals combine distinctive electronic, magnetic, and superconducting properties, making them promising for future quantum technologies. ...
Thomale's theory has now been directly substantiated for the first time in an international experiment, causing a worldwide sensation. This overturns the earlier assumption that Kagome metals could only host uniformly distributed Cooper pairs. ...
Previous research on Kagome metals has demonstrated both superconductivity and the spatial distribution of Cooper pairs. The surprising new finding is that these pairs can be distributed not just evenly, but also in a wave-like pattern within the atomic sublattices, a phenomenon termed "sublattice-modulated superconductivity." ..."
From the abstract:
"Superconductivity involving finite-momentum pairing can lead to spatial-gap and pair-density modulations, as well as Bogoliubov Fermi states within the superconducting gap. However, the experimental realization of their intertwined relations has been challenging. Here we detect chiral kagome superconductivity modulations with residual Fermi arcs in KV3Sb5 and CsV3Sb5 using normal and Josephson scanning tunnelling microscopy down to 30 millikelvin with a resolved electronic energy difference at the microelectronvolt level. We observe a U-shaped superconducting gap with flat residual in-gap states. This gap shows chiral 2a × 2a spatial modulations with magnetic-field-tunable chirality, which align with the chiral 2a × 2a pair-density modulations observed through Josephson tunnelling. These findings demonstrate a chiral pair density wave (PDW) that breaks time-reversal symmetry. Quasiparticle interference imaging of the in-gap zero-energy states reveals segmented arcs, with high-temperature data linking them to parts of the reconstructed vanadium d-orbital states within the charge order. The detected residual Fermi arcs can be explained by the partial suppression of these d-orbital states through an interorbital 2a × 2a PDW and thus serve as candidate Bogoliubov Fermi states. In addition, we differentiate the observed PDW order from impurity-induced gap modulations. Our observations not only uncover a chiral PDW order with orbital selectivity but also show the fundamental space–momentum correspondence inherent in finite-momentum-paired superconductivity."
From the abstract:
"We identify a superconducting order featuring spatial pair modulations on the kagome lattice subject to on-site Hubbard 𝑈 and nearest-neighbor 𝑉 interactions. Within our functional renormalization group analysis, this state appears with a concomitant 𝑑-wave superconducting (SC) instability at zero lattice momentum, where it distinguishes itself through intra-unit-cell modulations of the pairing function thus breaking the discrete space group symmetry. The relative weight of the sublattice modulated superconductor (SMS) and 𝑑-wave SC is influenced by the absolute interaction strength and coupling ratio 𝑉/𝑈. Parametrically adjacent to this domain at weak coupling, we find an intra-unit-cell modulated vestigial charge density wave and an 𝑠-wave SC instability. Our study provides a microscopic setting and thorough description of this novel SMS arising within a translation symmetry broken background."
Würzburg Theory Confirmed: Kagome Superconductor Makes Waves (original press release) "Superconductivity theory proposed by Würzburg physics team validated in international experiment: Cooper pairs display wave-like distribution in Kagome metals, enabling new technological applications like superconducting diodes."
Chiral kagome superconductivity modulations with residual Fermi arcs (no public access)
Sublattice modulated superconductivity in the kagome Hubbard model (no public access)
Figure 1:Kagome Fermiology and extended zone scheme.
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