Phason and Amplitudon in the Charge-Density-Wave Phase of One-Dimensional Charge Stripes in $\mathrmLa_2-x\mathrmSr_x\mathrmCuO_4$
The present systematic Raman scattering experiments reveal the phason and amplitudon of the charge density wave (CDW) mode in the charge stripes of La2-xSrxCuO4. Only about 15% of the electronic density of states condenses into the CDW state. The symmetries of the CDW modes change by the rotation of the stripes at the insulator-metal transition. The energy of the phason is finite at 0.06≤x≤0.1 and zero at x=0.035 and 0.115≤x≤0.135, which suggests that the CDW is commensurate at 0.06≤x≤0.1 and incommensurate otherwise. The zero-energy phason seems to reduce Tc at x=1/8.