11 research outputs found
Ultrafast measurements of mode-specific deformation potentials of BiTe and BiSe
Quantifying electron-phonon interactions for the surface states of
topological materials can provide key insights into surface-state transport,
topological superconductivity, and potentially how to manipulate the surface
state using a structural degree of freedom. We perform time-resolved x-ray
diffraction (XRD) and angle-resolved photoemission (ARPES) measurements on
BiTe and BiSe, following the excitation of coherent A
optical phonons. We extract and compare the deformation potentials coupling the
surface electronic states to local A-like displacements in these two
materials using the experimentally determined atomic displacements from XRD and
electron band shifts from ARPES.We find the coupling in BiTe and
BiSe to be similar and in general in agreement with expectations from
density functional theory. We establish a methodology that quantifies the
mode-specific electron-phonon coupling experimentally, allowing detailed
comparison to theory. Our results shed light on fundamental processes in
topological insulators involving electron-phonon coupling
Method for Accurate Determination of the Electron Contribution: Specific Heat of Ba0.59K0.41Fe2As2
Physical properties and electronic structure of a new barium titanate suboxide Ba1+δTi13−δO12 (δ = 0.11)
The structure, transport, thermodynamic properties, x-ray absorption spectra (XAS), and electronic structure of a new barium titanate suboxide, Ba1+δTi13−δO12 (δ = 0.11), are reported. It is a paramagnetic poor metal with hole carriers dominating the transport. Fermi liquid behavior appears at low temperature. The oxidization state of Ti obtained by the XAS is consistent with the metallic Ti2+ state. Local density approximation band structure calculations reveal the material is near the Van Hove singularity. The pseudogap behavior in the Ti-d band and the strong hybridization between the Ti-d and O-p orbitals reflect the characteristics of the building blocks of the Ti13 semi-cluster and the TiO4 quasi-squares, respectively
Spin-polarized surface resonances accompanying topological surface state formation.
Topological insulators host spin-polarized surface states born out of the energetic inversion of bulk bands driven by the spin-orbit interaction. Here we discover previously unidentified consequences of band-inversion on the surface electronic structure of the topological insulator Bi2Se3. By performing simultaneous spin, time, and angle-resolved photoemission spectroscopy, we map the spin-polarized unoccupied electronic structure and identify a surface resonance which is distinct from the topological surface state, yet shares a similar spin-orbital texture with opposite orientation. Its momentum dependence and spin texture imply an intimate connection with the topological surface state. Calculations show these two distinct states can emerge from trivial Rashba-like states that change topology through the spin-orbit-induced band inversion. This work thus provides a compelling view of the coevolution of surface states through a topological phase transition, enabled by the unique capability of directly measuring the spin-polarized unoccupied band structure
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Bogoliubov quasiparticle on the gossamer Fermi surface in electron-doped cuprates
Fermi surface reconstruction in electron-doped cuprates without antiferromagnetic long-range order
Ultrafast Measurements of Mode-Specific Deformation Potentials of Bi₂Te₃ and Bi₂Se₃
Quantifying electron-phonon interactions for the surface states of topological materials can provide key insights into surface-state transport, topological superconductivity, and potentially how to manipulate the surface state using a structural degree of freedom. We perform time-resolved x-ray diffraction (XRD) and angle-resolved photoemission (ARPES) measurements on Bi₂Te₃ and Bi₂Se₃, following the excitation of coherent A_1g optical phonons. We extract and compare the deformation potentials coupling the surface electronic states to local A_1g-like displacements in these two materials using the experimentally determined atomic displacements from XRD and electron band shifts from ARPES. We find the coupling in Bi₂Te₃ and Bi₂Se₃ to be similar and in general in agreement with expectations from density functional theory. We establish a methodology that quantifies the mode-specific electron-phonon coupling experimentally, allowing detailed comparison to theory. Our results shed light on fundamental processes in topological insulators involving electron-phonon coupling.ISSN:2160-330