Muon Spectroscopy Investigation of the Kagome Lattice

Abstract

In this thesis we use Muon Spin Rotation, Relaxation and Resonance (μSR) to probe the magnetic nature of the Kagome metal systems CsV3Sb5−xSnx (x = 0, 0.03, 0.10, 0.35), and YCr6Ge6. We obtained samples of CsV3Sb5−xSnx from colab- orators at UCSB and grew YCr6Ge6 at McMaster using the flux growth technique. We use direct current (DC) susceptibility, and x-ray diffraction techniques for ini- tial characterization of samples. Using DC susceptibility we verify CsV3Sb5−xSnx (x = 0, 0.03, 0.10, 0.35) shows superconductivity across all doping levels and CDW only when x = 0, 0.03. Our μSR examination of these materials shows evidence of multigap superconductivity in the first superconducting dome (x = 0, 0.03) and single gap superconductivity in the second dome (x = 0.1, 0.35). Additional zero field (ZF) measurements of the superconducting state show no evidence of time reversal symmetry breaking (TRSB) associated with the superconducting state. We also show evidence of a spontaneous change in the field distribution across all doping levels indicating an effect that is not associated with the bulk CDW transition. In DC susceptibility measurements of YCr6Ge6 we find evidence of a small magnetic effect at ≈ 1 K. Further investigation of this effect was carried out using μSR showing no evidence of a magnetic effect indicating that there was likely a dilute magnetic impurity. iii