Evidence of electron fractionalization from photoemission spectra in the high temperature superconductors

In the normal state of the high temperature superconductors Bi2Sr2CaCu2O8+delta and La2-xSrxCuO4, and in the related "stripe ordered" material, La1.25Nd0.6Sr0.5CuO4 there is sharp structure in the measured single hole spectral function, A(<)((k) over right arrow, omega), considered as a function of (k) over right arrow at fixed small binding energy omega. At the same time, as a function of w at fixed k on much of the putative Fermi surface, any structure in A(<)((k) over right arrow, omega), other than the Fermi cutoff. is very broad. This is characteristic of the situation in which there are no stable excitations with the quantum numbers of the electron, as is the case in the one-dimensional electron gas.