Ukuziphatha kwemigqa ye-Mohr namabhande ayisicaba kusayensi yesayensi ne-quantum physics ebizwa ngokuthi “I-Magic Angle” twisted bilayer graphene (TBLG) idonse isasasa elikhulu kososayensi, nakuba izakhiwo eziningi zibhekene nenkulumompikiswano eshubile. Ocwaningweni olusha olushicilelwe kujenali ye-Science Progress, u-Emilio Colledo kanye nososayensi eMnyangweni Wesayensi Yefiziksi Nezinto Zokusebenza e-United States nase-Japan babone ukusebenza kahle okukhulu nesifaniso ku-bilayer graphene esontiwe. I-Mott insulator state ine-engeli yokusonta ecishe ibe ngu-0.93 degrees. Le engeli incane ngo-15% kune-engeli “yomlingo” (1.1°) ebalwe ocwaningweni lwangaphambilini. Lolu cwaningo lubonisa ukuthi ububanzi "be-magic angle" ye-graphene ye-bilayer esontekile bukhulu kunalokho obekulindelwe ngaphambilini.
Lolu cwaningo lunikeza ingcebo yolwazi olusha lokucacisa izenzakalo eziqinile ze-quantum ku-bilayer graphene esontiwe ukuze kusetshenziswe ku-quantum physics. Izazi zefiziksi zichaza "i-Twistronics" njenge-engeli yokusonta ehlobene phakathi kwezingqimba eziseduze ze-van der Waals ukukhiqiza amabhendi e-moiré nama-flat ku-graphene. Lo mqondo usuphenduke indlela entsha neyingqayizivele yokushintsha kakhulu nokwenza ngendlela oyifisayo izakhiwo zedivayisi ngokusekelwe ezintweni ezinezinhlangothi ezimbili ukuze kuzuzwe ukugeleza kwamanje. Umthelela omangalisayo we-“Twistronics” waboniswa emsebenzini wokuphayona wabacwaningi, okubonisa ukuthi uma izendlalelo ezimbili ze-graphene zongqimba olulodwa zipakishwe “nge-magic angle” yokusonta engu-θ=1.1±0.1°, kuvela ibhande eliyisicaba kakhulu. .
Kulolu cwaningo, ku-twisted bilayer graphene (TBLG), isigaba sokuvikela se-microstrip yokuqala (isici sesakhiwo) se-superlattice "ku-magic angle" sigcwaliswe kancane. Ithimba labacwaningi linqume ukuthi lena i-Mott insulator (i-insulator enezakhiwo ze-superconducting) ebonisa ukusebenza kahle kakhulu kumazinga e-doping aphakeme kancane naphansi. Umdwebo wesigaba ubonisa izinga lokushisa eliphezulu eliphakeme phakathi kwezinga lokushisa lokushintsha kwe-superconducting (Tc) nezinga lokushisa le-Fermi (Tf). Lolu cwaningo luholele ekuthakaseleni okukhulu kanye nenkulumompikiswano yethiyori ngesakhiwo sebhendi ye-graphene, i-topology kanye nezinhlelo ezengeziwe ze-“Magic Angle” semiconductor. Uma kuqhathaniswa nombiko wetiyori wokuqala, ucwaningo lokuhlola aluvamile futhi lusanda kuqala. Kulolu cwaningo, ithimba lenze izilinganiso zokudlulisela "ku-magic angle" twisted bilayer graphene ebonisa izifunda ezifanele zokuvinjelwa kwe-insulating ne-superconducting.
I-engeli ehlanekezelwe ngokungalindelekile engu-0.93 ± 0.01, encane ngo-15% kune-"Magic Angle" esunguliwe, nayo incane kakhulu ebikiwe kuze kube manje futhi ikhombisa izakhiwo ze-superconducting. Le miphumela ibonisa ukuthi isimo esisha sokuhlobana singavela “Ku-Magic Angle” esontekile i-bilayer graphene, ngaphansi “ku-engeli yomlingo” eyinhloko, ngale kwe-microstrip yokuqala ye-graphene. Ukwakha lawa madivayisi e-bilayer e-bilayer asontekile, ithimba lisebenzise indlela "yokudabula nesitaki". Isakhiwo esiphakathi kwezingqimba ze-boron nitride (BN) ene-hexagonal sifakiwe; iphethini yejiyomethri ye-Hall rod enezintambo eziningi ezihlanganiswe no-Cr/Au (chromium/igolide) onqenqemeni loxhumana nabo. Yonke idivayisi ye-"Magic Angle" esontekile ye-bilayer ye-graphene yenziwe phezulu kwesendlalelo se-graphene esisetshenziswa njengesango elingemuva.
Ososayensi basebenzisa izindlela zokukhiya ezijwayelekile zamanje (DC) kanye nezishintshanisayo zamanje (AC) ukuze balinganise amadivayisi kuma-cryostats e-HE4 ampontshiwe kanye ne-HE3. Ithimba lirekhode ubudlelwano phakathi kokumelana ne-longitudinal yedivayisi (Rxx) kanye ne-voltage yesango enwetshiwe (VG) laphinde labala inkambu kazibuthe B ezingeni lokushisa elingu-1.7K. I-asymmetry encane ye-electron-hole ibonwe njengempahla yemvelo yedivayisi ye-graphene ye-bilayer “Magic Angle”. Njengoba kuphawulwe emibikweni edlule, ithimba lirekhode le miphumela futhi lachaza kabanzi ngemibiko ebilokhu yenza i-superconducting kuze kube manje. Isici esithi "I-Angle Yomlingo" sisonta i-engeli encane ye-torsion yedivayisi ye-bilayer graphene. Ngokuhlolisisa ishadi labalandeli be-Landau, abacwaningi bathole izici ezithile eziphawulekayo.
Isibonelo, ukuphakama ekugcwaliseni uhhafu kanye nokuwohloka okuphindwe kabili kweleveli ye-Landau kuhambisana nezimo zokuvala ezibonwa ngaphambilini ezifana ne-Moment. Ithimba libonise ikhefu ku-symmetry ye-spin valley SU(4) kanye nokwakheka kwendawo entsha ye-quasi-particle Fermi. Nokho, imininingwane idinga ukuhlolwa okuningiliziwe. Ukubukeka kwe-superconductivity kwabuye kwabonwa, okwandisa i-Rxx (ukumelana ne-longitudinal), efana nezifundo zangaphambilini. Iqembu libe selihlola izinga lokushisa elibucayi (Tc) lesigaba se-superconducting. Njengoba kungekho datha etholakele ye-doping ephelele yama-superconductors kuleli sampula, ososayensi bacabangele izinga lokushisa elibucayi elifinyelela ku-0.5K. Kodwa-ke, lawa madivayisi awasebenzi kuze kube yilapho esekwazi ukuthola idatha ecacile evela ku-superconducting state. Ukuze baqhubeke baphenye isimo se-superconducting, abacwaningi balinganise izici ezine-terminal voltage-current (VI) zedivayisi ngokuminyana kwenkampani yenethiwekhi.
Ukumelana okutholiwe kubonisa ukuthi i-super current ibonwa phezu kwebanga elikhulu lokuminyana futhi ikhombisa ukucindezelwa kwamandla amakhulu uma kusetshenziswa inkambu kazibuthe ehambisanayo. Ukuze bathole ukuqonda ngokuziphatha okubonwe ocwaningweni, abacwaningi babale ukwakheka kwebhendi ye-Moir yedivayisi ye-graphene esontekile ye-bilayer ye-bilayer isebenzisa imodeli ye-Bistritzer-MacDonald namapharamitha athuthukisiwe. Uma kuqhathaniswa nokubala kwangaphambilini kwe-engeli "Yomlingo", ibhendi ye-Moire yamandla aphansi ebaliwe ayihlukanisiwe nebhendi yamandla aphezulu. Nakuba i-engeli yokusonta yedivayisi incane kune-engeli “yomlingo” ebalwa kwenye indawo, idivayisi ine-engeli ehlobene kakhulu nezifundo zangaphambilini (I-Mort insulation and superconductivity), izazi zefiziksi ezizithole zingalindelekile futhi zingenzeka.
Ngemva kokuhlola okwengeziwe ukuziphatha ekuminyaniseni okukhulu (inani lezifunda ezitholakala kumandla ngamunye), izici ezibonwa ososayensi zibangelwa yizifunda ezisanda kuvela ezihlotshaniswayo zokuhlanganisa. Ngokuzayo, ucwaningo olunemininingwane eminingi lokuminyana kwezifunda (DOS) luzokwenziwa ukuze kuqondwe isimo esiyinqaba sokwahlukanisa futhi kunqunywe ukuthi zingahlukaniswa yini njengoketshezi lwe-quantum spin. Ngale ndlela, ososayensi babone i-superconductivity eduze nesimo sokuvikela esifana ne-Mox kudivayisi ye-graphene ye-bilayer esontekile ene-engeli encane yokusonta (0.93°). Lolu cwaningo lubonisa ukuthi ngisho nakuma-engeli amancane kanye nokuminyana okuphezulu, umphumela wokuhlanganiswa kwe-electron ezindaweni ze-moiré uyafana. Esikhathini esizayo, izigodi ze-spin zesigaba se-insulating zizofundwa, futhi isigaba esisha se-superconducting sizofundwa ekushiseni okuphansi. Ucwaningo lokuhlola luzohlanganiswa nemizamo yethiyori ukuze kuqondwe umsuka walokhu kuziphatha.
Isikhathi sokuthumela: Oct-08-2019