Opening a nodal gap by fluctuating spin-density-wave in lightly doped   La$_{2-x}$Sr$_x$CuO$_4$
  We investigate whether the spin or charge degrees of freedom are responsible for the nodal gap in underdoped cuprates by performing inelastic neutron scattering and x-ray diffraction measurements on La$_{2-x}$Sr$_x$CuO$_4$, which is on the edge of the antiferromagnetic phase. We found that fluctuating incommensurate spin-density-wave (SDW) with a the bottom part of an hourglass dispersion exists even in this magnetic sample. The strongest component of these fluctuations diminishes at the same temperature where the nodal gap opens. X-ray scattering measurements on the same crystal show no signature of charge-density-wave (CDW). Therefore, we suggest that the nodal gap in the electronic band of this cuprate opens due to fluctuating SDW with no contribution from CDW. 
Itzik Kapon, David S. Ellis, Gil Drachuck, Galina Bazalitski, Eugen   Weschke, Enrico Schierle, J\"org Strempfer, Christof N...
cond-mat.supr-con