arXiv subjects

Jessica L. McChesney

Publications and source records attributed to Jessica L. McChesney.

22 records · Page 2Linked to original sources

arXiv2008

Van Hove Singularity and Apparent Anisotropy in the Electron-Phonon Interaction in Graphene

We show that the electron-phonon coupling strength obtained from the slopes of the electronic energy vs. wavevector dispersion relations, as often done in analyzing angle-resolved photoemission data, can differ substantially from the actual electron-phonon coupling strength due to the curvature of the bare electronic bands. This effect becomes particularly important when the Fermi level is close to a van Hove singularity. By performing {\it ab initio} calculations on doped graphene we demonstrate that, while the apparent strength obtained from the slopes of experimental photoemission data is highly anisotropic, the angular dependence of the actual electron-phonon coupling strength in this material is negligible.

cond-mat.mtrl-sci↗

arXiv2007

Scanning tunneling spectroscopy of inhomogeneous electronic structure in monolayer and bilayer graphene on SiC

We present a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface. Low voltage topographic images reveal fine, atomic-scale carbon networks, whereas higher bias images are dominated by emergent spatially inhomogeneous large-scale structure similar to a carbon-rich reconstruction of SiC(0001). STS spectroscopy shows a ~100meV gap-like feature around zero bias for both monolayer and bilayer graphene/SiC, as well as significant spatial inhomogeneity in electronic structure above the gap edge. Nanoscale structure at the SiC/graphene interface is seen to correlate with observed electronic spatial inhomogeneity. These results are important for potential devices involving electronic transport or tunneling in graphene/SiC.

cond-mat.str-el↗

arXiv2007

Symmetry Breaking in Few Layer Graphene Films

Recently, it was demonstrated that the quasiparticle dynamics, the layer-dependent charge and potential, and the c-axis screening coefficient could be extracted from measurements of the spectral function of few layer graphene films grown epitaxially on SiC using angle-resolved photoemission spectroscopy (ARPES). In this article we review these findings, and present detailed methodology for extracting such parameters from ARPES. We also present detailed arguments against the possibility of an energy gap at the Dirac crossing ED.

cond-mat.str-el↗

arXiv2007

Massive enhancement of electron-phonon coupling in doped graphene by an electronic singularity

The nature of the coupling leading to superconductivity in layered materials such as high-Tc superconductors and graphite intercalation compounds (GICs) is still unresolved. In both systems, interactions of electrons with either phonons or other electrons or both have been proposed to explain superconductivity. In the high-Tc cuprates, the presence of a Van Hove singularity (VHS) in the density of states near the Fermi level was long ago proposed to enhance the many-body couplings and therefore may play a role in superconductivity. Such a singularity can cause an anisotropic variation in the coupling strength, which may partially explain the so-called nodal-antinodal dichotomy in the cuprates. Here we show that the topology of the graphene band structure at dopings comparable to the GICs is quite similar to that of the cuprates and that the quasiparticle dynamics in graphene have a similar dichotomy. Namely, the electron-phonon coupling is highly anisotropic, diverging near a saddle point in the graphene electronic band structure. These results support the important role of the VHS in layered materials and the possible optimization of Tc by tuning the VHS with respect to the Fermi level.

cond-mat.str-el↗