9 research outputs found
Tailoring the thermal Casimir force with graphene
The Casimir interaction is omnipresent source of forces at small separations between bodies, which is difficult to change by varying external conditions. Here we show that graphene interacting with a metal can have the best known force contrast to the temperature and the Fermi level variations. In the distance range 50–300 nm the force is measurable and can vary a few times for graphene with a bandgap much larger than the temperature. In this distance range the main part of the force is due to the thermal fluctuations. We discuss also graphene on a dielectric membrane as a technologically robust configuration
Competition between excitonic gap generation and disorder scattering in graphene
We study the disorder effect on the excitonic gap generation caused by strong
Coulomb interaction in graphene. By solving the self-consistently coupled
equations of dynamical fermion gap and disorder scattering rate ,
we found a critical line on the plane of interaction strength and
disorder strength . The phase diagram is divided into two regions: in the
region with large and small , and ; in the
other region, and for nonzero . In particular, there
is no coexistence of finite fermion gap and finite scattering rate. These
results imply a strong competition between excitonic gap generation and
disorder scattering. This conclusion does not change when an additional contact
four-fermion interaction is included. For sufficiently large , the
growing disorder may drive a quantum phase transition from an excitonic
insulator to a metal.Comment: 8 pages, 1 figur
Electron-Phonon Coupling in Highly-Screened Graphene
Photoemission studies of graphene have resulted in a long-standing
controversy concerning the strength of the experimental electron-phonon
interaction in comparison with theoretical calculations. Using high-resolution
angle-resolved photoemission spectroscopy we study graphene grown on a copper
substrate, where the metallic screening of the substrate substantially reduces
the electron-electron interaction, simplifying the comparison of the
electron-phonon interaction between theory and experiment. By taking the
nonlinear bare bandstructure into account, we are able to show that the
strength of the electron-phonon interaction does indeed agree with theoretical
calculations. In addition, we observe a significant bandgap at the Dirac point
of graphene.Comment: Submitted to Phys. Rev. Lett. on July 20, 201
Effect of Coulomb interactions on the physical observables of graphene
We give an update of the situation concerning the effect of electron-electron
interactions on the physics of a neutral graphene system at low energies. We
revise old renormalization group results and the use of 1/N expansion to
address questions of the possible opening of a low-energy gap, and the
magnitude of the graphene fine structure constant. We emphasize the role of
Fermi velocity as the only free parameter determining the transport and
electronic properties of the graphene system and revise its renormalization by
Coulomb interactions in the light of recent experimental evidence.Comment: Proceedings of the Nobel Symposium on graphene 2010, to appear as a
special issue in Physica Script
Electron-Electron Interactions in Graphene: Current Status and Perspectives
We review the problem of electron-electron interactions in graphene. Starting
from the screening of long range interactions in these systems, we discuss the
existence of an emerging Dirac liquid of Lorentz invariant quasi-particles in
the weak coupling regime, and strongly correlated electronic states in the
strong coupling regime. We also analyze the analogy and connections between the
many-body problem and the Coulomb impurity problem. The problem of the magnetic
instability and Kondo effect of impurities and/or adatoms in graphene is also
discussed in analogy with classical models of many-body effects in ordinary
metals. We show that Lorentz invariance plays a fundamental role and leads to
effects that span the whole spectrum, from the ultraviolet to the infrared. The
effect of an emerging Lorentz invariance is also discussed in the context of
finite size and edge effects as well as mesoscopic physics. We also briefly
discuss the effects of strong magnetic fields in single layers and review some
of the main aspects of the many-body problem in graphene bilayers. In addition
to reviewing the fully understood aspects of the many-body problem in graphene,
we show that a plethora of interesting issues remain open, both theoretically
and experimentally, and that the field of graphene research is still exciting
and vibrant.Comment: Review Article to appear in Reviews of Modern Physics. 62 pages, 44
figure
Emergent spin liquids in the hubbard model on the anisotropic honeycomb lattice
10.1209/0295-5075/95/47013EPL954