Zhihui Pan

Coexistence of competing orders with two energy gaps in real and momentum space in the high temperature superconductor Bi2Sr2-xLaxCuO6+δ

Through a combined scanning tunneling microscopy and angle-resolved photoemission spectroscopy study, we report the observation of two distinct gaps (a small and a large gap) that coexist both in real space and in the antinodal region of momentum space, below the superconducting transition temperature (Tc )o fBi2Sr2� xLaxCuO6þ� . We show that the small gap is associated with superconductivity. The largegap persists above Tc, and seems linked to observed charge ordering. We find a strong correlation between the large and small gaps suggesting that they are affected by similar physical processes.

Electronic Structure of Superconducting KC8 and Nonsuperconducting LiC6 Graphite Intercalation Compounds: Evidence for a Graphene-Sheet-Driven Superconducting State

We have performed photoemission studies of the electronic structure in LiC(6) and KC(8), a nonsuperconducting and a superconducting graphite intercalation compound, respectively. We have found that the charge transfer from the intercalant layers to graphene layers is larger in KC(8) than in LiC(6), opposite of what might be expected from their chemical composition. We have also measured the strength of the electron-phonon interaction on the graphene-derived Fermi surface to carbon derived phonons in both materials and found that it follows a universal trend where the coupling strength and superconductivity monotonically increase with the filling of graphene π(*) states. This correlation suggests that both graphene-derived electrons and graphene-derived phonons are crucial for superconductivity in graphite intercalation compounds.

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.

Nature of oxygen dopant-induced states in high-temperature Bi2Sr2CaCu2O8+x superconductors : A photoemission investigation

We have performed an angular-resolved photoemission study of underdoped, optimally doped and overdoped Bi

Evolution of Fermi surface and normal-state gap in the chemically substituted cuprates Bi2Sr2-xBixCuO6+delta

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Fermi Surface Evolution and Luttinger Theorem in NaxCoO2: A Systematic Photoemission Study

Sr

High-energy kink observed in the electron dispersion of high-temperature cuprate superconductors.

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Universal quasiparticle decoherence in hole- and electron-doped high-Tc cuprates

CaCu

Spin resolved photoemission on surface doped topological insulator Bi

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