Evidence for the heavy-fermion normal state of high-temperature superconductors from the theory of spectroscopy

We show that recent angle-resolved photoemission and inverse photoemission spectra of ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_8$ agree well with a numerical theory with no adjustable parameters based on the heavy-fermion normal state. The band structure deduced from the angle-resolved photoemission is in essential accord with the calculation. The three most obvious features of the inverse photoemission spectrum, the Fermi edge, the large width of the empty portion of the band, and the satellite at 2–3 eV are in agreement with the calculation. These agreements support the heavy-fermion state as the normal state of this material.