Measurement of the surface susceptibility and the surface conductivity of atomically thin MoS2\rm MoS_2 by spectroscopic ellipsometry

We show how to correctly extract from the ellipsometric data the surface susceptibility and the surface conductivity that describe the optical properties of monolayer $\rm MoS_2$. Theoretically, these parameters stem from modelling a single-layer two-dimensional crystal as a surface current, a truly two-dimensional model. Currently experimental practice is to consider this model equivalent to a homogeneous slab with an effective thickness given by the interlayer spacing of the exfoliating bulk material. We prove that the error in the evaluation of the surface susceptibility of monolayer $\rm MoS_2$, owing to the use of the slab model, is at least 10% or greater, a significant discrepancy in the determination of the optical properties of this material.Comment: Keywords: Ellipsometry, graphene, MoS2, two dimensional crystals, optical contrast, absorption, transition metal dichalcogenide monolayer

Measurements of the surface susceptibility and conductivity of atomically thin MoS2 and WS2 by spectroscopic ellipsometry

The optical properties of a monolayer MoS2 or WS2 are described in literature by a bulk dielectric function. The material is modelled as a homogeneous medium with an effective thickness given by the interlayer spacing of the exfoliating bulk material. This model has been considered equivalent to the surface current model where the monolayer material is described as a truly two-dimensional system. Here we prove experimentally that for a monolayer MoS2 and WS2 the two models are not equivalent. We show how to correctly extract from the experimental data the surface susceptibility and the surface conductivity that describe the optical properties of a monolayer MoS

Five-body calculation of s-wave n-4He scattering at next-to-leading order pionless effective field theory

We present the first five-body calculations of s-wave n-4He scattering within leading order and next-to-leading order (NLO) pionless effective field theory (π̸EFT). Using an harmonic oscillator trap technique and π̸EFT fitted to just six well-established experimental parameters, we predict the s-wave n-4He phase shifts, scattering length an4He1/2(NLO)=2.47(4num.)(17theor.)fm, and effective range rn4He1/2(NLO)=1.384(3num.)(211theor.)fm in agreement with experiment. The apparent cutoff independence of our results is used to estimate the theoretical errors coming as an integral part of our final results

Effective field theory analysis of the Coulomb breakup of the one-neutron halo nucleus 19 C

We analyse the Coulomb breakup of 19 C measured at 67A MeV at RIKEN. We use the Coulomb-Corrected Eikonal (CCE) approximation to model the reaction and describe the one-neutron halo nucleus 19 C within Halo Effective Field Theory (Halo EFT). At leading order we obtain a fair reproduction of the measured cross section as a function of energy and angle. The description is insensitive to the choice of optical potential, as long as it accurately represents the size of 18 C. It is also insensitive to the interior of the 19 C wave function. Comparison between theory and experiment thus enables us to infer asymptotic properties of the ground state of 19 C: these data put constraints on the one-neutron separation energy of this nucleus and, for a given binding energy, can be used to extract an asymptotic normalisation coefficient (ANC). These results are confirmed by CCE calculations employing next-to-leading order Halo EFT descriptions of 19 C: at this order the results for the Coulomb breakup cross section are completely insensitive to the choice of the regulator. Accordingly, this reaction can be used to constrain the one-neutron separation energy and ANC of 19 C.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effective field theory analysis of the Coulomb breakup of the one-neutron halo nucleus 19^{19}C

International audienceWe analyse the Coulomb breakup of 19C measured at 67A MeV at RIKEN. We use the Coulomb-Corrected Eikonal (CCE) approximation to model the reaction and describe the one-neutron halo nucleus 19C within Halo Effective Field Theory (EFT). At leading order we obtain a fair reproduction of the measured cross section as a function of energy and angle. The description is insensitive to the choice of optical potential, as long as it accurately represents the size of 18C. It is also insensitive to the interior of the 19C wave function. Comparison between theory and experiment thus enables us to infer asymptotic properties of the ground state of 19C: these data put constraints on the one-neutron separation energy of this nucleus and, for a given binding energy, can be used to extract an asymptotic normalisation coefficient (ANC). These results are confirmed by CCE calculations employing next-to-leading order Halo EFT descriptions of 19C: at this order the results for the Coulomb breakup cross section are completely insensitive to the choice of the regulator. Accordingly, this reaction can be used to constrain the one-neutron separation energy and ANC of 19C