The BEM combined with the time-stepping scheme is employed in the fully nonlinear numerical calculation of 2-D free surface flow generated by large amplitude oscillation of rocker flap wavemaker. Special consideratio...The BEM combined with the time-stepping scheme is employed in the fully nonlinear numerical calculation of 2-D free surface flow generated by large amplitude oscillation of rocker flap wavemaker. Special consideration is paid on the compatibility of free surface and body surface conditions at the intersection point. In the case study of weakly nonlinear regular wave, the comparison of elevations and hydrodynamic moments acting on the flap from the fully nonlinear calculation,second-order calculation in frequency domain and linear calculation in time domain is made, and the agreement indicates the feasibility of the numerical approach of the fully nonlinear calculation.展开更多
It is well-known that exciton effects are determinant to understanding the optical absorption spectrum of low-dimensional materials.However,the role of excitons in nonlinear optical responses has been much less invest...It is well-known that exciton effects are determinant to understanding the optical absorption spectrum of low-dimensional materials.However,the role of excitons in nonlinear optical responses has been much less investigated at the experimental level.Additionally,computational methods to calculate nonlinear conductivities in real materials are still not widespread,particularly taking into account excitonic interactions.We present a methodology to calculate the excitonic second-order optical responses in 2D materials relying on:(i)ab initio tight-binding Hamiltonians obtained by Wannier interpolation and(ii)solving the Bethe-Salpeter equation with effective electron-hole interactions.Here,in particular,we explore the role of excitons in the shift current of monolayer materials.Focusing on MoS_(2)and GeS monolayer systems,our results show that 2p-like excitons,which are dark in the linear response regime,yield a contribution to the photocurrent comparable to that of 1s-like excitons.Under radiation with intensity~104W/cm2,the excitonic theory predicts in-gap photogalvanic currents of almost~10 nA in sufficiently clean samples,which is typically one order of magnitude higher than the value predicted by independent-particle theory near the band edge.展开更多
文摘The BEM combined with the time-stepping scheme is employed in the fully nonlinear numerical calculation of 2-D free surface flow generated by large amplitude oscillation of rocker flap wavemaker. Special consideration is paid on the compatibility of free surface and body surface conditions at the intersection point. In the case study of weakly nonlinear regular wave, the comparison of elevations and hydrodynamic moments acting on the flap from the fully nonlinear calculation,second-order calculation in frequency domain and linear calculation in time domain is made, and the agreement indicates the feasibility of the numerical approach of the fully nonlinear calculation.
基金support from the Spanish MICINN(grants nos.PID2019-109539GB-C43,TED2021-131323B-I00,and PID2022-141712NB-C21)the María de Maeztu Program for Units of Excellence in R&D(grant no.CEX2018-000805-M)+2 种基金the Comunidad Autónoma de Madrid through the Recovery,Transformation and Resilience Plan from Spain,the NextGenerationEU plan from the European Union(MAD2D-CM-UAM7)the Generalitat Valenciana through Programa Prometeo(2021/017)The authors thankfully acknowledge RES resources provided by Universidad de Málaga in Picasso to FI-2024-2-0016.M.A.García-Blázquez acknowledges financial support from Universidad Autónoma de Madrid through an FPI-UAM grant.M.C.-G.is grateful to the Azrieli Foundation for the award of an Azrieli International Postdoctoral Fellowship.Additional computational resources were provided by the Weizmann Institute of Science at Chemfarm.M.C.-G.thanks Tonatiuh Rangel for providing the initial geometries of bulk and monolayer GeS.
文摘It is well-known that exciton effects are determinant to understanding the optical absorption spectrum of low-dimensional materials.However,the role of excitons in nonlinear optical responses has been much less investigated at the experimental level.Additionally,computational methods to calculate nonlinear conductivities in real materials are still not widespread,particularly taking into account excitonic interactions.We present a methodology to calculate the excitonic second-order optical responses in 2D materials relying on:(i)ab initio tight-binding Hamiltonians obtained by Wannier interpolation and(ii)solving the Bethe-Salpeter equation with effective electron-hole interactions.Here,in particular,we explore the role of excitons in the shift current of monolayer materials.Focusing on MoS_(2)and GeS monolayer systems,our results show that 2p-like excitons,which are dark in the linear response regime,yield a contribution to the photocurrent comparable to that of 1s-like excitons.Under radiation with intensity~104W/cm2,the excitonic theory predicts in-gap photogalvanic currents of almost~10 nA in sufficiently clean samples,which is typically one order of magnitude higher than the value predicted by independent-particle theory near the band edge.
