Unoccupied surface band tuning

抄録

It is interesting to see how surface modification or reconstruction can be used to manipulate the physical properties and electronic properties of unoccupied states on solid surfaces. An important representative of unoccupied surface states is the image potential state. This state exhibits unique characteristics, such as long lifetime and strong confinement near the surface, making it valuable for understanding the forces experienced by the electron in the vicinity of the metal.

In condensed matter physics, the periodicity of atoms results in the opening of bandgaps, a common occurrence. However, the image potential state has not shown bandgap opening due to the long-range periodic potential within the material. Nevertheless, surface reconstruction, such as the formation of a (5x1) superstructure with Iridium (Ir), can potentially affect the image potential state by introducing additional confinement and modifying electron wavefunctions.

In this study, we have employed two-photon photoemission (2PPE) spectroscopy to investigate the states above the Fermi level. Our observations revealed that the Ir(001)-(5x1) reconstructed surface exhibits a band gap, which arises from the surface reconstruction, whereas such a band gap is not seen on Ir(001)-(1x1) surface. This difference can be attributed to the distinct surface reconstructions of the two structures. This study of the Ir system with surface reconstructions, such as the (5x1) superstructure, offers a platform to investigate electronic properties and phenomena associated with confined electron dynamics.