Search for orbital magnetism in the kagome superconductor CsV3Sb5 using neutron diffraction

As many kagome metals, the topological superconductor AV3Sb5 with (A = K,Rb,Cs) hosts a charge density wave. A related chiral flux phase that breaks the time-reversal symmetry has been further theoretically predicted in these materials. The flux phase is associated with loop currents that produce ordered orbital magnetic moments, which would occur at the momentum points, M, characterizing the charge-density wave state. Polarized neutron-diffraction experiments have been performed on an assembly of single crystals of CsV3Sb5 to search for such orbital magnetic moments. No evidence for the existence of a three-dimensionally ordered moment is found at any temperature at the first M1 = (1/2,0,0) point in the Brillouin zone within an excellent experimental uncertainty, i.e., m = 0 +/- 0.01 mu B per vanadium atom. However, the data might be suggestive of a putative magnetic orbital moment in the second Brillouin zone at M2 = (1/2,1/2,0) at the detection limit of the experiment. Some loop currents patterns flowing only on vanadium triangles are able to account for this finding suggesting an ordered orbital magnetic moment of, at most, <^>0.02 +/- 0.01 mu B per vanadium triangle.