Kev vam meej tau ua nyob rau hauv txoj kev kawm ntawm ultrafast motion ntawm Weil quasiparticles tswj los ntawmlasers
Nyob rau hauv xyoo tas los no, theoretical thiab kev sim tshawb fawb ntawm topological quantum xeev thiab topological quantum cov ntaub ntawv tau dhau los ua lub ntsiab lus kub nyob rau hauv lub teb ntawm condensed teeb meem physics.Raws li lub tswv yim tshiab ntawm kev faib cov teeb meem, kev txiav txim topological, zoo li symmetry, yog ib lub tswv yim tseem ceeb hauv cov teeb meem physics.Kev nkag siab tob ntawm topology muaj feem xyuam nrog cov teeb meem hauv cov teeb meem condensed physics, xws li cov qauv hluav taws xob hauv tsev.quantum theem, quantum theem hloov thiab excitation ntawm ntau yam immobilized nyob rau hauv quantum theem.Hauv cov ntaub ntawv topological, kev sib txuas ntawm ntau qib ntawm kev ywj pheej, xws li electrons, phonons thiab spin, plays lub luag haujlwm txiav txim siab hauv kev nkag siab thiab tswj cov khoom siv.Lub teeb excitation tuaj yeem siv los txiav txim siab qhov sib txawv ntawm kev sib cuam tshuam thiab tswj lub xeev ntawm cov teeb meem, thiab cov ntaub ntawv hais txog cov khoom siv lub cev lub cev, kev hloov pauv ntawm cov qauv, thiab cov xeev quantum tshiab tuaj yeem tau txais.Tam sim no, kev sib raug zoo ntawm tus cwj pwm macroscopic ntawm cov ntaub ntawv topological uas tau tsav los ntawm lub teeb teb thiab lawv cov qauv microscopic atomic thiab cov khoom hluav taws xob tau dhau los ua lub hom phiaj tshawb fawb.
Lub photoelectric teb tus cwj pwm ntawm cov ntaub ntawv topological yog ze ze rau nws cov qauv hluav taws xob microscopic.Rau topological semi-hlau, cov cab kuj excitation nyob ze ntawm lub band kev sib tshuam yog heev rhiab heev rau lub yoj nta ntawm lub system.Txoj kev tshawb no ntawm nonlinear optical phenomena nyob rau hauv topological semi-hlau yuav pab tau kom peb to taub zoo dua lub cev lub zog ntawm lub siab lub xeev ntawm lub system, thiab nws xav tias cov teebmeem no yuav siv tau nyob rau hauv lub tsim ntawmcov khoom siv kho qhov muagthiab tsim cov hnub ci hlwb, muab cov kev siv tau zoo rau yav tom ntej.Piv txwv li, nyob rau hauv ib tug Weyl semi-hlau, absorbing ib tug photon ntawm ncig polarized lub teeb yuav ua rau lub kiv tig, thiab nyob rau hauv thiaj li yuav ua tau raws li kev txuag ntawm angular momentum, lub electron excitation ntawm ob sab ntawm lub Weyl cone yuav asymmetrically faib raws. cov kev taw qhia ntawm lub voj voog polarized lub teeb propagation, uas yog hu ua chiral xaiv txoj cai (Daim duab 1).
Txoj kev kawm theoretical ntawm nonlinear optical phenomena ntawm cov ntaub ntawv topological feem ntau siv cov txheej txheem ntawm kev sib txuas cov kev suav ntawm cov khoom hauv av hauv lub xeev cov khoom thiab symmetry tsom xam.Txawm li cas los xij, txoj kev no muaj qee qhov tsis xws luag: nws tsis muaj cov ntaub ntawv tseem ceeb ntawm lub sijhawm tiag tiag ntawm cov neeg nqa khoom zoo siab hauv qhov chaw nrawm thiab qhov chaw tiag tiag, thiab nws tsis tuaj yeem tsim kom muaj kev sib piv ncaj qha nrog lub sijhawm daws teeb meem kev sim ntsuas.Kev sib txuas ntawm electron-phonons thiab photon-phonons tsis tuaj yeem xav txog.Thiab qhov no yog qhov tseem ceeb rau qee theem kev hloov pauv tshwm sim.Tsis tas li ntawd, qhov kev soj ntsuam theoretical no raws li perturbation theory tsis tuaj yeem cuam tshuam nrog cov txheej txheem ntawm lub cev nyob rau hauv lub teeb pom kev zoo.Lub sij hawm-dependent density functional molecular dynamics (TDDFT-MD) simulation raws li thawj lub hauv paus ntsiab lus yuav daws tau cov teeb meem saum toj no.
Tsis ntev los no, raws li kev taw qhia los ntawm tus kws tshawb fawb Meng Sheng, postdoctoral researcher Guan Mengxue thiab tus kws kho mob tub ntxhais kawm Wang En ntawm SF10 Group ntawm lub xeev tseem ceeb Laboratory ntawm Surface Physics ntawm lub koom haum ntawm Physics ntawm Suav Academy ntawm Sciences / Beijing National Research Center for Concentrated Matter Physics, koom tes nrog Xib Fwb Sun Jiatao ntawm Beijing Institute of Technology, lawv tau siv tus kheej tsim kev zoo siab rau lub xeev kev ua haujlwm simulation software TDAP.Cov yam ntxwv teb ntawm quastiparticle excitation rau ultrafast laser nyob rau hauv ob hom Weyl semi-hlau WTe2 raug soj ntsuam.
Nws tau raug pom tias kev xaiv excitation ntawm cov neeg nqa khoom ze ntawm Weyl taw tes yog txiav txim siab los ntawm atomic orbital symmetry thiab txoj cai kev hloov pauv, uas txawv ntawm txoj cai xaiv spin xaiv rau chiral excitation, thiab nws txoj kev excitation tuaj yeem tswj tau los ntawm kev hloov cov kev taw qhia polarization. ntawm linearly polarized lub teeb thiab photon zog (Daim duab 2).
Lub asymmetric excitation ntawm cov neeg nqa khoom induces photocurrents nyob rau hauv sib txawv cov lus qhia nyob rau hauv tiag tiag qhov chaw, uas cuam tshuam rau cov kev taw qhia thiab symmetry ntawm lub interlayer plam ntawm lub system.Txij li thaum cov khoom topological ntawm WTe2, xws li cov naj npawb ntawm Weyl cov ntsiab lus thiab cov degree ntawm kev sib cais nyob rau hauv lub momentum qhov chaw, yog heev nyob rau hauv lub symmetry ntawm lub system (Daim duab 3), asymmetric excitation ntawm cov cab kuj yuav ua rau txawv tus cwj pwm ntawm Weyl. quastiparticles nyob rau hauv lub zog ntawm qhov chaw thiab hloov pauv nyob rau hauv lub topological zog ntawm lub system.Yog li, txoj kev tshawb no muab ib daim duab qhia meej rau theem phototopological hloov pauv (Daim duab 4).
Cov txiaj ntsig tau pom tias chirality ntawm cov cab kuj excitation ze Weyl point yuav tsum tau them nyiaj mloog mus rau, thiab lub atomic orbital zog ntawm yoj muaj nuj nqi yuav tsum tau soj ntsuam.Cov teebmeem ntawm ob yog qhov zoo sib xws tab sis cov txheej txheem yog qhov sib txawv, uas muab lub hauv paus rau kev piav qhia txog cov ntsiab lus ntawm Weyl cov ntsiab lus.Tsis tas li ntawd, txoj kev xam pom uas tau txais los ntawm txoj kev tshawb no tuaj yeem nkag siab tob txog kev sib cuam tshuam thiab kev coj cwj pwm tsis zoo ntawm qib atomic thiab hluav taws xob hauv lub sijhawm nrawm nrawm, nthuav tawm lawv cov txheej txheem microphysical, thiab xav tias yuav yog lub cuab yeej muaj zog rau kev tshawb fawb yav tom ntej ntawm nonlinear optical phenomena nyob rau hauv cov ntaub ntawv topological.
Cov txiaj ntsig yog nyob rau hauv phau ntawv Journal Nature Communications.Kev tshawb fawb ua haujlwm tau txais kev txhawb nqa los ntawm National Key Research thiab Development Plan, National Natural Science Foundation thiab Strategic Pilot Project (Category B) ntawm Suav Academy of Sciences.
FIG.1.a.Txoj cai xaiv chirality rau Weyl cov ntsiab lus nrog qhov zoo chirality kos npe (χ=+1) nyob rau hauv lub voj voog polarized;Kev xaiv excitation vim atomic orbital symmetry ntawm Weyl point ntawm b.χ = + 1 hauv on-line polarized teeb
FIG.2. Atomic qauv daim duab ntawm a, Td-WTe2;b.Band qauv ze ntawm Fermi nto;(c) Band qauv thiab cov txheeb ze koom nrog ntawm atomic orbitals faib raws cov kab sib luag siab hauv cheeb tsam Brillouin, cov xub (1) thiab (2) sawv cev rau kev zoo siab nyob ze lossis deb ntawm Weyl cov ntsiab lus, feem;d.Amplification ntawm band qauv raws Gamma-X kev taw qhia
FIG.3.ab: Tus txheeb ze interlayer txav ntawm linearly polarized lub teeb polarization kev taw qhia raws A-axis thiab B-axis ntawm cov siv lead ua, thiab cov qauv txav sib thooj yog qhia;C. Kev sib piv ntawm theoretical simulation thiab sim soj ntsuam;de: Symmetry evolution ntawm lub system thiab txoj hauj lwm, tus naj npawb thiab degree ntawm kev sib cais ntawm ob qhov ze tshaj Weyl ntsiab lus nyob rau hauv lub kz = 0 dav hlau
FIG.4. Phototopological theem hloov nyob rau hauv Td-WTe2 rau linearly polarized lub teeb photon zog (?) ω) thiab polarization kev taw qhia (θ) nyob ntawm theem daim duab
Post lub sij hawm: Sep-25-2023