Workshop "NMR, µSR, Mössbauer spectroscopies in the study of Fe-based and other unconventional high-Tc superconductors"
Determination of muon sites with Density Functional Theory
Pietro Bonfà, Universitá degli Studi di Parma, Italy
Two issues may arise when µSR is used to characterize the magnetic ground state of a sample. One is the determination of the muon stopping site(s). Indeed, a precise knowledge of the muon embedding position in the crystal is essential in order to estimate the magnetic moments of the atoms in the sample. The second concern is related to the local perturbation produced by the muon implantation. While it is usually correct to assume the muon to be a passive probe, there are well know cases in which µSR results may only be understood by considering the muon local modications of the crystalline environment . The use of Density Functional Theory (DFT) to study the muon sites and perturbations caused by muons in a host is rapidly picking up speed [1 - 5]. In this contribution we shall review the approaches and the main results obtained so far. These include the study of F--F centers in fluorides, the identification of muon sites in iron pnictides superconductors, plus the very recent works on MnSi and La2CuO4.
FIG. 1: The muon site in T' La2CuO4 is represented with an isosurface of its probability density.
 F. Bernardini et al., Phys. Rev. B 87, 115148 (2013); J. S. Möller et al., Phys. Rev. B 87, 121108 (2013)
 S. J. Blundell et al., Phys. Rev. B 88, 064423 (2013)
 J. S. Möller et al., Phys. Scr. 88, 068510 (2013)
 R. De Renzi et al., Supercond. Sci. Tech. 25, 084009 (2012)
 M. Bendele et al., Phys. Rev. B 85, 064517 (2012)