Kupita patsogolo kwachitika pakuphunzira za kuyenda mofulumira kwambiri kwa ma quasiparticles a Weil omwe amalamulidwa ndima laser
M'zaka zaposachedwapa, kafukufuku wa chiphunzitso ndi zoyeserera pa topological quantum states ndi topological quantum materials wakhala nkhani yofunika kwambiri pankhani ya condensed matter physics. Monga lingaliro latsopano la kugawa zinthu, topological order, monga symmetry, ndi lingaliro lofunikira mu condensed matter physics. Kumvetsetsa kwakukulu kwa topology kumakhudzana ndi mavuto oyambira mu condensed matter physics, monga kapangidwe ka zamagetsi kamagawo a kwantamu, kusintha kwa gawo la quantum ndi kusonkhezera kwa zinthu zambiri zosayenda bwino mu magawo a quantum. Mu zinthu za topological, kulumikizana pakati pa madigiri ambiri a ufulu, monga ma elekitironi, ma phononi ndi kuzungulira, kumakhala ndi gawo lofunika kwambiri pakumvetsetsa ndikuwongolera katundu wa zinthu. Kusonkhezera kwa kuwala kungagwiritsidwe ntchito kusiyanitsa pakati pa kuyanjana kosiyana ndikusintha momwe zinthu zilili, ndipo chidziwitso chokhudza katundu woyambira wa zinthuzo, kusintha kwa gawo la kapangidwe kake, ndi momwe zinthu zatsopano za quantum zimakhalira chingapezeke. Pakadali pano, ubale pakati pa machitidwe a macroscopic a zinthu za topological zomwe zimayendetsedwa ndi gawo la kuwala ndi kapangidwe kake ka atomu kakang'ono komanso katundu wamagetsi wakhala cholinga chofufuza.
Kachitidwe ka photoelectric ka mayankho a zinthu za topological kamagwirizana kwambiri ndi kapangidwe kake ka microscopic electronic. Pa topological semi-metals, carrier excitation pafupi ndi malo olumikizirana a band imakhudzidwa kwambiri ndi mawonekedwe a mafunde a dongosololi. Kuphunzira za zochitika zosakhala za mzere mu topological semi-metals kungatithandize kumvetsetsa bwino za thupi la zinthu zosangalatsidwa za dongosololi, ndipo akuyembekezeka kuti zotsatirazi zitha kugwiritsidwa ntchito popangazipangizo zowunikirandi kapangidwe ka maselo a dzuwa, zomwe zingathandize mtsogolo. Mwachitsanzo, mu Weyl semi-metal, kuyamwa fotoni ya kuwala kozungulira kozungulira kudzapangitsa kuti kuzungulira kutembenuke, ndipo kuti kukwaniritse kusungidwa kwa angular momentum, kusuntha kwa ma electron mbali zonse ziwiri za Weyl cone kudzagawidwa mozungulira motsatira njira yofalikira kwa kuwala kozungulira kozungulira, komwe kumatchedwa chiral selection rule (Chithunzi 1).
Kafukufuku wa chiphunzitso cha zinthu zosawoneka bwino za zinthu za topological nthawi zambiri amagwiritsa ntchito njira yophatikiza kuwerengera kwa zinthu zomwe zili pansi ndi kusanthula kwa symmetry. Komabe, njira iyi ili ndi zolakwika zina: ilibe chidziwitso cha nthawi yeniyeni cha zinthu zonyamula zinthu zomwe zimakhudzidwa mu malo a momentum ndi malo enieni, ndipo singathe kufananiza mwachindunji ndi njira yoyesera yodziwira nthawi. Kulumikizana pakati pa ma electron-phonons ndi ma photon-phonons sikungaganizidwe. Ndipo izi ndizofunikira kwambiri kuti kusintha kwina kwa gawo kuchitike. Kuphatikiza apo, kusanthula kwa chiphunzitso kumeneku kozikidwa pa chiphunzitso cha perturbation sikungathe kuthana ndi njira zakuthupi pansi pa mphamvu ya kuwala. Kuyerekeza kwa nthawi komwe kumadalira kuchuluka kwa mphamvu yamagetsi (TDDFT-MD) kutengera mfundo zoyambirira kumatha kuthetsa mavuto omwe ali pamwambapa.
Posachedwapa, motsogozedwa ndi wofufuza Meng Sheng, wofufuza wa postdoctoral Guan Mengxue ndi wophunzira wa udokotala Wang En wa SF10 Group of the State Key Laboratory of Surface Physics of the Institute of Physics of the Chinese Academy of Sciences/Beijing National Research Center for Concentrated Matter Physics, mogwirizana ndi Pulofesa Sun Jiatao wa Beijing Institute of Technology, adagwiritsa ntchito pulogalamu yodzipangira yokha ya excited state dynamics simulation TDAP. Makhalidwe a yankho la quastiparticle excitation ku ultrafast laser mu mtundu wachiwiri wa Weyl semi-metal WTe2 akufufuzidwa.
Zawonetsedwa kuti kusuntha kwa zinthu zomwe zimanyamula zinthu pafupi ndi malo a Weyl kumatsimikiziridwa ndi lamulo la atomic orbital symmetry ndi transition selection, lomwe ndi losiyana ndi lamulo lachizolowezi la spin selection la chiral excitation, ndipo njira yake yosuntha zinthu imatha kulamulidwa mwa kusintha njira ya polarization ya linearly polarized light ndi photon energy (Chithunzi 2).
Kusakaniza kwa asymmetric kwa onyamula kumayambitsa ma photocurrents m'njira zosiyanasiyana mumlengalenga weniweni, zomwe zimakhudza njira ndi kusinthasintha kwa kutsetsereka kwa interlayer kwa dongosolo. Popeza makhalidwe a topological a WTe2, monga kuchuluka kwa mfundo za Weyl ndi kuchuluka kwa kulekana mumlengalenga, zimadalira kwambiri kusakanikirana kwa dongosolo (Chithunzi 3), kusakaniza kwa asymmetric kwa onyamula kudzabweretsa machitidwe osiyanasiyana a Weyl quastiparticles mumlengalenga ndi kusintha kofanana mu mawonekedwe a topological a dongosolo. Chifukwa chake, kafukufukuyu amapereka chithunzi chomveka bwino cha kusintha kwa gawo la phototopological (Chithunzi 4).
Zotsatira zake zikusonyeza kuti chirality ya carrier excitation pafupi ndi Weyl point iyenera kuganiziridwa, ndipo mphamvu za atomiki zozungulira za ntchito ya mafunde ziyenera kufufuzidwa. Zotsatira za ziwirizi ndizofanana koma njira yake ndi yosiyana, zomwe zimapereka maziko a chiphunzitso pofotokozera kusiyana kwa mfundo za Weyl. Kuphatikiza apo, njira yowerengera yomwe idagwiritsidwa ntchito mu kafukufukuyu imatha kumvetsetsa bwino kuyanjana kovuta ndi machitidwe osinthika pamlingo wa atomiki ndi zamagetsi mwachangu kwambiri, kuwulula njira zawo zazing'ono, ndipo ikuyembekezeka kukhala chida champhamvu chofufuzira mtsogolo pa zochitika zosakhala za mzere m'zinthu za topological.
Zotsatira zake zili mu magazini ya Nature Communications. Ntchito yofufuzayi ikuthandizidwa ndi National Key Research and Development Plan, National Natural Science Foundation ndi Strategic Pilot Project (Gulu B) la Chinese Academy of Sciences.
CHITHUNZI 1.a. Lamulo losankha chirality la ma point a Weyl okhala ndi chizindikiro chabwino cha chirality (χ=+1) pansi pa kuwala kozungulira kozungulira; Kusangalatsa kosankha chifukwa cha kusinthasintha kwa atomiki pa malo a Weyl a b. χ=+1 mu kuwala kozungulira kozungulira
Chithunzi 2. Chithunzi cha kapangidwe ka atomu cha a, Td-WTe2; b. Kapangidwe ka gulu pafupi ndi pamwamba pa Fermi; (c) Kapangidwe ka gulu ndi zopereka za ma orbital a atomu omwe amagawidwa m'mizere yofanana kwambiri m'chigawo cha Brillouin, mivi (1) ndi (2) ikuyimira kusangalatsa pafupi kapena kutali ndi mfundo za Weyl, motsatana; d. Kukulitsa kapangidwe ka gulu motsatira njira ya Gamma-X
CHITHUNZI 3.ab: Kusuntha kwapakati pa zigawo za kuwala kolumikizana mozungulira mozungulira A-axis ndi B-axis ya kristalo, ndi njira yoyendera yofananira ikusonyezedwa; C. Kuyerekeza pakati pa kuyerekezera kwa chiphunzitso ndi kuwona kwa kuyesa; de: Kusintha kwa dongosolo ndi malo, chiwerengero ndi digiri ya kulekanitsidwa kwa mfundo ziwiri zapafupi za Weyl mu ndege ya kz=0
CHITHUNZI 4. Kusintha kwa gawo la Phototopological mu Td-WTe2 kwa mphamvu ya photon yowala mopingasa (?) ω) ndi chithunzi cha gawo lodalira polarization (θ)
Nthawi yotumizira: Sep-25-2023