Detection of precursor charge-density-wave order in 2H-NbSe2 by muSR
We demonstrate the sensitivity of transverse-field muon spin rotation (TF-muSR) to static charge-density-wave (CDW) order in the bulk of 2H-NbSe2. In the presence of CDW order the quadrupolar interaction of the 93Nb nuclei with the local electric-field gradient is modified, and this in turn affects the magnetic dipolar coupling of the positive muon to these nuclei. For a weak magnetic field applied parallel to the c-axis, we observe a small enhancement of the muon depolarization rate at temperatures below the established CDW phase transition. Aligning the applied field perpendicular to the c-axis, we observe a sensivity to static CDW order in regions of the sample extending up to nearly 3 times the CDW transition temperature. The results suggest that the muon is mobile over the temperature range explored above the superconducting transition temperature (Tc), and becomes trapped in the vicinity of defects.