Two pseudogaps with different energy scales at the antinode of the high-temperature Bi2Sr2CuO6 superconductor using angle-resolved photoemission spectroscopy

We performed high-resolution angle-resolved photoemission spectroscopy on single-layered cuprate Bi2Sr2CuO6 to clarify the origin of the pseudogap. By using various photon energies, we succeeded in directly observing two different pseudogaps with two different energy scales which coexist in the antinodal region: one reflects the d(x2-y2)-wave pairing strength while the other has a larger energy scale suggesting an origin distinct from superconductivity. The observed two-pseudogap behavior provides a key to fully understanding the pseudogap phenomena in cuprates.