Laboratoire Léon Brillouin,CEA Saclay,91191 Gif sur Yvette,France

报告摘要：

The kagome metal, CsV₃Sb₅, exhibits both a charge density wave phase below 94K with a 2x2 doubling of the unit cell and a superconducting phase below 2.5K. These materials also show strong anomalous Hall effect, but no spin ordering has been found in these materials both by muon spin spectroscopy and neutron diffraction. To explain this without relying on spins, the possibility of an orbital magnetism coming from a loop current phase, emerging alongside the charge density wave, has been theoretically predicted. This phase exhibits some similarities with the current loop phase predicted and observed in cuprates. To check for the presence of this loop current phase in kagome materials, we carried out polarized neutron diffraction experiments on the IN22 (CRG-CEA) triple-axis spectrometer located at ILL-Grenoble. This measurement was experimentally challenging and went close to the limit in accuracy obtainable with polarised neutron diffraction in a reasonable time. Most models predict loop currents to produce magnetic intensity at M₁ = [1/2 0 L] or M₂ = [1/2 1/2 L] reciprocal space positions with L = {0,1/2}. We investigated both momentum positions. For the first one, no magnetic signal was observed ruling out the possibility of having a magnetic moment larger than 0.01 μB by vanadium atoms. However, measurements at M₂ do not exclude the possibility of a magnetic signal, suggesting a moment of only 0.02 ± 0.01 μB per unit cell. This shows that current models have to be refined whether toward a lowering of the expected magnetic moment or toward a different loop current pattern giving rise to magnetic intensity at different reciprocal space positions to be compatible with our measurements [1].

[1] William Liege et al.,Phys. Rev. B 110,195109 (2024).

报告人简介：

William Liege made his master graduation in 2023 at the Grenoble University. He is doing now a PhD at Laboratoire Leon Brillouin with Philippe Bourges about loop currents in cuprates and kagome superconductors. His talk will be about the kagome superconductor,CsV₃Sb₅.

联系人：李源 研究员