Plasmons, collective excitations of charge density, have attracted much interest in fundamental science and applications. While plasmons have been observed in metal-like phase of high-Tc superconductors, they have not been… Click to show full abstract
Plasmons, collective excitations of charge density, have attracted much interest in fundamental science and applications. While plasmons have been observed in metal-like phase of high-Tc superconductors, they have not been reported in the Mott-insulating form. Here, we report a new quantum correlated plasmons in ambipolar Y1–zLaz(Ba1–xLax)2Cu3Oy and optimal-doped YBa2Cu3O7–x using high-resolution spectroscopic ellipsometry. Interestingly, as functions of hole, electron-doping, and temperature, their dynamical loss-function and dielectric-functions exhibit formation of two plasmons at multiple ordered low- and high-photon energies due to on-site Cu3d Coulomb interaction and antibonding O2p–Cu3d. While the low-energy correlated plasmon transforms into a conventional-plasmon upon doping, the high-energy correlated plasmon remains. The intensity of these plasmons follows a mixture of singlet and triplet with decreasing temperature. Besides, their dephasing time decreases with increasing doping. Our result hig...
               
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