  The ab plane optical spectra of two single crystals of La(2-x)Sr(x)Cu(4), one
overdoped and one underdoped, were investigated. We observe a gap-like
depression of the effective scattering rate below 700 cm(-1) in both systems.
This feature persists up to 300 K in the underdoped sample with the
concentration of Sr x=0.14 but loses prominance at temperatures above 300 K in
the overdoped regime (x=0.22). Below 700 cm(-1) the scattering rate is
temperature dependent and superlinear in frequency for both samples. Above this
frequency the effective scattering rate becomes linear in frequency and is
temperature independent in the case of the underdoped La(1.86)Sr(0.14)CuO(4) up
to 300 K. On the other hand, the overdoped La(1.76)Sr(0.22)CuO(4) shows a
scattering rate temperature dependence above 700 cm(-1) at all temperatures.
This behaviour of the frequency and temperature dependent scattering rates is a
signature of a pseudogap state in other HTSC materials and suggests that both
the under and overdoped single-layer HTSC systems Ls(2-x)Sr(x)CuO(4) have a
pseudogap at temperatures exceeding 300 K.

Superconductivity;Strongly Correlated Electrons