Disordered Fermi Liquid in Epitaxial Graphene from Quantum Transport Measurements

Abstract

We have performed magnetotransport measurements on monolayer epitaxial graphene and analyzed them in the framework of the disordered Fermi liquid theory. We have separated the electron-electron and weak-localization contributions to resistivity and demonstrated the phase coherence over a micrometer length scale, setting the limit of at least 50 ps on the spin relaxation time in this material.Funding Agencies|Swedish Research Council||Foundation for Strategic Research||UK National Measurement Office||EU|

Weak localization scattering lengths in epitaxial, and CVD graphene

“…For the elastic intervalley scattering term L i , we find a weak trend with carrier density with a negative exponent of −0.173. Previous temperature 9,11 and backgate studies 11 found no strong variation of L i with either temperature or carrier density. Given that L i is due to short range, atomically sharp scatterers and device-edge scattering, it would be expected to be highly dependent on the device characteristics.…”

“…These terms do have a carrier density dependence, however, the fitting parameters were found to vary with carrier density. Lara-Avila et al 9 use an alternative model and find their data to be well modeled by the addition of a electron spin-flip scattering term. This is due to scattering from the localized magnetic moment of spin-carrying defects which is likely to be dependent on the sample preparation method and could mask or dominate underlying trends in the dependence of the phase coherence length on carrier density.…”

“…Previous work has typically found similar values for L ϕ of around 0.6 μm. [9][10][11][12] In Ki et al, 11 there has been some previous work carried out on the carrier density dependence by using a single sample with a backgate. In their work they found a superlinear increase of L ϕ with carrier density.…”

“…(1) and these were converted to scattering lengths using, L ϕ,i, * = τ ϕ,i, * D. Figure 3 shows the extracted scattering lengths, from our data and from the literature. [9][10][11][12] Care was taken to extract all values for as close as possible to the same temperature, in this case 1.5 K. This is done since L ϕ in particular is known to vary strongly with temperature. [9][10][11][12] Fits to the data are made using a simple power law, Bn A , the results of which are shown in Table I.…”

“…Devices are analyzed from graphene produced by epitaxial growth on SiC 7 and chemical vapor deposition (CVD) onto thin metal films. 8 The results are compared with those obtained from the literature [9][10][11][12] and together are used to measure trends in the scattering lengths with carrier density.…”