Experimental Observation of the Crystallization of a Paired Holon State

An excitation at 201 meV is observed in the doped-hole ladder cuprate Sr(14)Cu(24)O(41), using ultraviolet resonance Raman scattering with incident light at 3.7 eV polarized along the rungs. The excitation is of charge nature, with a temperature independent excitation energy, and can be understood via an intraladder pair-breaking process. The intensity tracks closely the order parameter of the charge density wave in the ladder CDW(L), but persists above its transition temperature T(CDWL), indicating a strong local pairing above the T(CDWL). The 201 meV excitation vanishes in La(6)Ca(8)Cu(24)O(41+delta), and La(5)Ca(9)Cu(24)O(41) which are samples with no holes in the ladders. Our results suggest that the doped holes in the ladder are composite bosons consisting of paired holons that order below T(CDW).