Imyitwarire y'imirongo ya Mohr n'imikandara igororotse mu bumenyi bwa siyansi na fiziki ya kwantumu yitwa "Magic Angle" twisted bilayer graphene (TBLG) yakuruye amatsiko menshi y'abahanga mu bya siyansi, nubwo imiterere myinshi ihura n'ibiganiro bikomeye. Mu bushakashatsi bushya bwasohotse mu kinyamakuru Science Progress, Emilio Colledo n'abahanga mu ishami rya fiziki n'ibikoresho muri Leta Zunze Ubumwe za Amerika no mu Buyapani babonye superconductivity na asparations muri twisted bilayer graphene. State ya Mott insulator ifite inguni ya twist ya dogere 0.93. Iyi nguni ni ntoho 15% ugereranyije na inguni ya "magic angle" (1.1°) yabazwe mu bushakashatsi bwabanje. Ubu bushakashatsi bwerekana ko "magic angle" ya twisted bilayer graphene ni nini kuruta uko byari byitezwe mbere.
Ubu bushakashatsi butanga amakuru mashya menshi yo gusobanura ibintu bikomeye bya quantum muri graphene ya bilayer ihindagurika mu mikoreshereze muri fiziki ya quantum. Abahanga mu bya fiziki basobanura "Twistronics" nk'inguni ihindagurika hagati y'ibice byegeranye bya van der Waals kugira ngo hakorwe imigozi ya moiré n'ibice bigororotse muri graphene. Iki gitekerezo cyabaye uburyo bushya kandi budasanzwe bwo guhindura no guhindura imiterere y'ibikoresho bishingiye ku bikoresho bifite imiterere ibiri kugira ngo hagerwe ku muvuduko w'amashanyarazi. Ingaruka zitangaje za "Twistronics" zagaragajwe mu murimo w'abashakashatsi, bigaragaza ko iyo ibice bibiri bya graphene bifite urwego rumwe bishyizwe hamwe ku nguni ya "magic angle" ya θ = 1.1 ± 0.1 °, hagaragara umugozi ugororotse cyane.
Muri ubu bushakashatsi, muri graphene ya bilayer ya twisted (TBLG), igice cyo gukingira cy’umuyoboro wa mbere wa microstrip (imiterere) ya superlattice ku "nguni y’ubumaji" cyari cyuzuyemo ibice bibiri. Itsinda ry’ubushakashatsi ryasanze iyi ari Mott insulator (insulator ifite ubushobozi bwo gukwirakwiza superconducting) igaragaza superconductivity ku rwego rwo hejuru gato no hasi rw’ingufu zikoreshwa mu gukwirakwiza doping. Imbonerahamwe y’icyiciro igaragaza superconductor y’ubushyuhe bwinshi hagati y’ubushyuhe bw’impinduka ya superconducting (Tc) n’ubushyuhe bwa Fermi (Tf). Ubu bushakashatsi bwatumye habaho amatsiko menshi n’impaka ku miterere ya graphene band, topology n’izindi sisitemu za semiconductor za "Magic Angle". Ugereranyije na raporo y’umwimerere y’ubushakashatsi, ubushakashatsi bw’igerageza ni gake kandi butangiye. Muri ubu bushakashatsi, itsinda ryakoze ibipimo byo kohereza kuri "nguni y’ubumaji" ya bilayer twisted bilayer igaragaza imiterere ijyanye no gukwirakwiza no gukwirakwiza superconducting.
Inguni yahinduwe mu buryo butunguranye ya 0.93 ± 0.01, ikaba ari ntoya kuri 15% ugereranyije na "Magic Angle" yashyizweho, nayo niyo ntoya cyane kugeza ubu kandi igaragaza imiterere ya superconducting. Ibi byavuye mu bushakashatsi bigaragaza ko imiterere mishya y'isano ishobora kugaragara muri "Magic Angle" twisted bilayer graphene, iri munsi y'"inguni y'ubumaji" y'ibanze, inyuma ya microstrip ya mbere ya graphene. Kugira ngo hubakwe ibi bikoresho bya "magic horn" twisted bilayer graphene, itsinda ryakoresheje uburyo bwa "tear and stack". Imiterere iri hagati y'ibice bya hexagonal boron nitride (BN) ifunze; ishushanyije mu ishusho ya Hall rod geometry ifite insinga nyinshi zifatanye n'imigozi ya Cr/Au (chromium/gold). Igikoresho cyose cya "Magic Angle" twisted bilayer graphene cyakozwe hejuru y'urwego rwa graphene rwakoreshejwe nk'irembo ry'inyuma.
Abahanga mu bya siyansi bakoresha uburyo busanzwe bwo gufunga umuyoboro w’amashanyarazi ugororotse (DC) n’uburyo bwo gufunga umuyoboro w’amashanyarazi usimburana (AC) kugira ngo bapime ibikoresho muri pompe ya HE4 na HE3 cryostats. Itsinda ryanditse isano iri hagati y’ubudahangarwa bw’igikoresho (Rxx) n’umuvuduko wa voltage yagutse y’irembo (VG) kandi ryabaruye imbaraga za rukuruzi B ku bushyuhe bwa 1.7K. Ubusumbane bw’umwobo muto wa electron-hole bwagaragaye ko ari umwihariko w’igikoresho cya “Magic Angle” twisted bilayer graphene. Nkuko byagaragaye muri raporo zabanje, itsinda ryanditse ibi bisubizo kandi risobanura raporo zimaze igihe kinini zikora cyane kugeza ubu. “Magic Angle” iranga ihindura inguni ntoya ya torsion y’igikoresho cya bilayer graphene. Basuzumye neza imbonerahamwe y’abafana ba Landau, abashakashatsi babonye ibintu bimwe na bimwe bizwi.
Urugero, uburebure bw'umuvuduko ku gice cya kabiri cy'umuvuduko n'ubushyuhe bubiri bw'urwego rwa Landau bihuye n'imiterere y'ubushyuhe bwagaragaye mbere. Itsinda ryagaragaje ko hari icyuho mu buryo bungana bwa SU (4) ya spin valley ndetse no kurema ubuso bushya bwa Fermi. Ariko, ibisobanuro birambuye bisaba igenzura rirambuye. Isura ya superconductivity nayo yagaragaye, byatumye Rxx (ubudahangarwa bw'igihe kirekire), nk'uko byakozwe mbere. Itsinda ryasuzumye ubushyuhe bw'ingenzi (Tc) bw'icyiciro cya superconductivity. Kubera ko nta makuru yabonetse yo gukoresha superconductors neza muri iki cyitegererezo, abahanga batekereje ubushyuhe bw'ingenzi bugera kuri 0.5K. Ariko, ibi bikoresho ntibikora kugeza igihe bishoboye kubona amakuru asobanutse neza aturutse muri superconductor. Kugira ngo barusheho gukora ubushakashatsi ku miterere ya superconductor, abashakashatsi bapimye imiterere ya voltage-current (VI) y'igikoresho ku bucucike butandukanye bw'umuvuduko.
Ubudahangarwa bwabonetse bwerekana ko imbaraga zidasanzwe zigaragara ku rugero runini rw’ubucucike kandi bwerekana ko imbaraga zidasanzwe zigabanuka iyo ingufu zidasanzwe zikoreshejwe. Kugira ngo bamenye neza imyitwarire yagaragaye muri ubu bushakashatsi, abashakashatsi babaze imiterere y’icyuma cya Moir cy’igikoresho cya “Magic Angle” twisted bilayer graphene bakoresheje icyitegererezo cya Bistritzer-MacDonald ndetse n’ibipimo byanoze. Ugereranyije n’ibarwa ryabanje ry’inguni ya “Magic Angle”, imbaraga nke za Moire band ntizitandukanijwe n’imbaraga nyinshi. Nubwo inguni ya twist y’igikoresho ari nto ugereranyije n’inguni ya “magic angle” yabazwe ahandi, igikoresho gifite ikintu gifitanye isano cyane n’ubushakashatsi bwabanje (Mort insulation and superconductivity), abahanga mu bya fiziki basanze ari ikintu kitunguranye kandi gishoboka.
Nyuma yo gusuzuma imyitwarire ku bucucike bunini (umubare w'imiterere iboneka kuri buri ngufu), imiterere yagaragaye n'abahanga mu bya siyansi iterwa n'imiterere mishya y'ubucucike. Mu gihe kizaza, hazakorwa inyigo irambuye ku bucucike bw'imiterere (DOS) kugira ngo basobanukirwe imiterere idasanzwe y'ubucucike no kumenya niba ishobora gushyirwa mu byiciro bya quantum spin liquids. Muri ubu buryo, abahanga mu bya siyansi babonye superconductivity hafi ya Mox-like insulation state mu gikoresho cya graphene cya bilayer twisted gifite inguni ntoya (0.93°). Ubu bushakashatsi bwerekana ko no ku nguni nto n'ubucucike bwinshi, ingaruka z'isano rya electron ku miterere ya moiré ari zimwe. Mu gihe kizaza, hazakorwa inyigo ku miraba ya spin y'igice cya insulation, kandi hazaba hari ikindi gice gishya cya superconductor kizigwa ku bushyuhe buri hasi. Ubushakashatsi bw'igerageza buzahuzwa n'ingamba z'inyigisho kugira ngo basobanukirwe inkomoko y'iyi myitwarire.
Igihe cyo kohereza: Ukwakira-08-2019