Polarization Flipping of Even-Order Harmonics in Monolayer Transition-Metal Dichalcogenides
作者机构：Stanford PULSE InstituteSLAC National Accelerator LaboratoryMenlo ParkCA 94025USA Department of Applied PhysicsStanford UniversityStanfordCA 94305USA Max Planck Institute for the Physics of Complex SystemsNöthnitzer Str.3801187 DresdenGermany Department of Materials Science and EngineeringStanford UniversityStanfordCA 94305USA Department of ChemistryStanford UniversityStanfordCA 94305USA Department of Photon ScienceStanford UniversityStanfordCA 94305USA
出 版 物：《Ultrafast Science》 (超快科学（英文）)
年 卷 期：2021年第1卷第1期
页 面：39-47页
学科分类：080901[工学-物理电子学] 0809[工学-电子科学与技术（可授工学、理学学位）] 08[工学] 080401[工学-精密仪器及机械] 0804[工学-仪器科学与技术] 0803[工学-光学工程] 0702[理学-物理学]
基 金：supported by the US Department of Energy Office of Science Basic Energy Sciences Chemical Sciences Geosciences and Biosciences Division through the AMOS program.F.L.was supported by a Terman Fellowship and startup funds from the Department of Chemistry at Stanford University.Y.K.acknowledges support from the UrbanekChodorow Fellowship from Stanford University.C.H.acknowledges support from the W.M.Keck Foundation and a Humboldt Research Fellowship
主 题：polarization harmonics mirror
摘 要：We present a systematic study of the crystal-orientation dependence of high-harmonic generation in monolayer transition-metal dichalcogenides,WS2 and MoSe2,subjected to intense linearly polarized midinfrared laser *** measured spectra consist of both odd-and even-order harmonics,with a high-energy cutoff extending beyond the 15th order for a laser-field strength around~1 V/*** WS2,we find that the polarization direction of the odd-order harmonics smoothly follows that of the laser field irrespective of the crystal orientation,whereas the direction of the even-order harmonics is fixed by the crystal mirror ***,the polarization of the even-order harmonics shows a flip in the course of crystal rotation when the laser field lies between two of the crystal mirror *** numerically solving the semiconductor Bloch equations for a gapped-graphene model,we qualitatively reproduce these experimental features and find the polarization flipping to be associated with a significant contribution from interband *** contrast,high-harmonic signals from MoSe2 exhibit deviations from the laser-field following of oddorder harmonics and crystal-mirror-plane following of even-order *** attribute these differences to the competing roles of the intraband and interband contributions,including the deflection of the electron-hole trajectories by nonparabolic crystal bands.
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