Angle-resolved Photoemission Spectroscopy Line Shapes Research Articles

Mobile small polarons and the Peierls transition in the quasi-one-dimensional conductorK0.3MoO3

High-resolution angle-resolved photoemission spectroscopy (ARPES) on the quasi-one-dimensional Peierls system K0.3MoO3 reveals a hidden open Fermi surface and band features displaying the symmetry properties of the underlying lattice. However, the ARPES line shapes and optical data suggest that the corresponding quasiparticles are heavily renormalized by strong electron-phonon interactions. The temperature dependence of the leading edge of the mostly incoherent spectrum bears signatures of the Peierls transition at T-P=180 K and of pretransitional fluctuations.

Theoretical photoemission line shapes and many body correlations

Angle resolved photoemission spectroscopy (ARPES) of high temperature superconductors has revealed an unusual behavior of line width and line shape, which has been interpreted as an indication for a Fermi liquid like ground state. The prototype for investigations of such ARPES line shapes in normal conductors is the isolated, strong and nearly non-dispersive Ti-3d derived emission near the Fermi level of the quasi twodimensional, metallic layer compound TiTe 2[1,2]. Comparing experimental photoemission data only with the initial states spectral density, a decision in favor of a Fermi liquid is not fully conclusive. Furthermore, that comparison shows a deviation from the Fermi liquid behavior in the vicinity of the M point, because of neglecting band structure effects. In order to clarify this problem we performed full theoretical calculations of photoemission spectra within the onestep model. For the initial states standard parametrizations of the Fermi liquid selfenergy were chosen. The resulting energy distribution curves for several angles of emission are reported. In addition many body effects in the final states were considered by properly calculating the optical potential in the GW-approximation.

Fermi-liquid line shapes measured by angle-resolved photoemission spectroscopy on 1-T-TiTe2.

We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) on the layered compound 1-T-${\mathrm{TiTe}}_{2}$, whose low-energy properties are those of a normal metal, and analyzed the experimental line shapes in terms of the Fermi-liquid self-energy. We find excellent agreement between the measured and theoretical spectral weight distribution, while line profiles expected for other theoretical models such as the marginal Fermi liquid clearly fail to reproduce the experimental spectra. This demonstrates that ARPES line shapes are able to reflect the nature of an interacting electron system.