Imyitwarire yimigozi ya Mohr nu mukandara uringaniye mubumenyi bwa siyanse na fiziki ya kwantike yitwa "Magic Angle" yahinduwe na bilayer graphene (TBLG) yashimishije abahanga, nubwo imitungo myinshi ihura nimpaka zikomeye. Mu bushakashatsi bushya bwasohotse mu kinyamakuru Science Progress, Emilio Colledo n'abahanga bo mu ishami rya siyansi y’ubumenyi n’ibikoresho muri Amerika no mu Buyapani barebeye hamwe birenze urugero no kugereranya muri graphene ya bilayeri. Leta ya Mott insulator ifite impande zingana na dogere 0,93. Iyi mfuruka ni ntoya 15% kurenza “magic angle” inguni (1.1 °) ibarwa mubushakashatsi bwabanje. Ubu bushakashatsi bwerekana ko "magic angle" urwego rwa bilayeri graphene ihindagurika ni nini kuruta uko byari byitezwe mbere.
Ubu bushakashatsi butanga amakuru menshi yo gusobanura ibintu bikomeye bya kwant muri graphene ya bilayeri igoretse kugirango ikoreshwe muri fiziki ya kwant. Abahanga mu bya fiziki basobanura “Twistronics” nk'impande igereranije hagati ya van der Waals yegeranye kugirango itange moiré hamwe na bande ya graphene. Iki gitekerezo cyahindutse uburyo bushya kandi budasanzwe bwo guhindura no gutunganya ibikoresho byibikoresho bishingiye kubikoresho-bibiri kugirango bigerweho neza. Ingaruka zidasanzwe za “Twistronics” zagaragaye mu murimo w'ubupayiniya bw'abashakashatsi, byerekana ko iyo ibice bibiri bya graphene imwe igizwe na “magic angle” impande zombi za θ = 1.1 ± 0.1 °, hagaragara umurongo uhamye cyane. .
Muri ubu bushakashatsi, muri graphene ya bilayeri yahinduwe (TBLG), icyiciro cyo gukingira microstrip ya mbere (imiterere yimiterere) ya superlattice kuri "magic angle" yari yuzuye igice. Itsinda ry’ubushakashatsi ryemeje ko iyi ari insimburangingo ya Mott (insulator ifite imiterere irenze urugero) yerekana imbaraga zidasanzwe hejuru ya doping yo hejuru. Igishushanyo cyerekana icyiciro cy'ubushyuhe bwo hejuru hagati yubushyuhe bwikirenga (Tc) nubushyuhe bwa Fermi (Tf). Ubu bushakashatsi bwatumye abantu bashishikazwa cyane n’impaka zishingiye ku miterere ya bande ya graphene, topologiya hamwe na sisitemu ya “Magic Angle” yiyongera. Ugereranije na raporo yumwimerere, ubushakashatsi bwikigereranyo ntibusanzwe kandi bwatangiye. Muri ubu bushakashatsi, itsinda ryakoze ibipimo byo kwanduza kuri “magic angle” ihindagurika ya bilayeri graphene yerekana leta zijyanye no gukumira no gukabya.
Inguni yagoretse mu buryo butunguranye bwa 0,93 ± 0.01, ikaba ntoya 15% ugereranije na “Magic Angle” yashizweho, nayo ni ntoya yatangajwe kugeza ubu kandi yerekana ibintu birenze urugero. Ibisubizo byerekana ko imiterere mishya ifitanye isano ishobora kugaragara muri "Magic Angle" yahinduwe na bilayeri graphene, munsi ya "magic angle" y'ibanze, hejuru ya microstrip ya mbere ya graphene. Kubaka aya "mahembe yubumaji" yagoretse bilayeri graphene, itsinda ryakoresheje uburyo bwo "kurira no gutondeka". Imiterere iri hagati ya nitride ya boron itandatu (BN) ikubiyemo; yashushanyije muri Hall inkoni ya geometrie hamwe ninsinga nyinshi zifatanije na Cr / Au (chromium / zahabu) impande zombi. Igikoresho cyose cyitwa "Magic Angle" cyahinduwe na bilayeri graphene igikoresho cyahimbwe hejuru ya graphene yakoreshejwe nk'irembo ry'inyuma.
Abahanga bakoresha amashanyarazi asanzwe (DC) hamwe nubundi buryo bwo gufunga amashanyarazi (AC) kugirango bapime ibikoresho muma pompe ya HE4 na HE3. Iri tsinda ryanditse isano iri hagati yo kurwanya igikoresho kirekire (Rxx) n’umurongo mugari wa voltage (VG) kandi babaze umurima wa rukuruzi B ku bushyuhe bwa 1.7K. Gitoya ya electron-umwobo asimmetrie yagaragaye ko ari umutungo wihariye wa "Magic Angle" igoretse ya bilayer graphene. Nkuko byagaragaye muri raporo zabanjirije iyi, itsinda ryanditse ibisubizo kandi rirambuye raporo zagiye zirenga kugeza ubu. Ikiranga "Magic Angle" ihinduranya inguni ntoya ya bors ya graphene. Hamwe nogusuzuma neza imbonerahamwe yabafana ba Landau, abashakashatsi bungutse ibintu bimwe bigaragara.
Kurugero, impinga kuri kimwe cya kabiri yuzura hamwe ninshuro ebyiri kwangirika kurwego rwa Landau bihuye nibisanzwe byarebaga Ibihe bisa nkibisanzwe. Iri tsinda ryerekanye ko ryacitse mu buringanire bw’ikigereranyo cya spin (4) no gushiraho ubuso bushya bwa Fermi. Ariko, ibisobanuro bisaba ubugenzuzi burambuye. Kugaragara kwa superconductivity nabyo byagaragaye, byongera Rxx (resistance longitudinal resistance), bisa nubushakashatsi bwabanje. Itsinda ryasuzumye ubushyuhe bukomeye (Tc) bwicyiciro cya superconducting. Kubera ko nta makuru yabonetse kugirango doping ikoreshwe neza muri iyi sample, abahanga bafashe ubushyuhe bukabije bugera kuri 0.5K. Nyamara, ibyo bikoresho biba ingirakamaro kugeza igihe bizabasha kubona amakuru asobanutse muri leta irenze urugero. Kugira ngo turusheho gukora iperereza kuri leta irenze urugero, abashakashatsi bapimye ibintu bine biranga voltage-amashanyarazi (VI) biranga igikoresho ku bucucike butandukanye.
Kurwanya byabonetse byerekana ko super current igaragara hejuru yubunini bunini kandi ikerekana guhagarika super super mugihe ikoreshwa rya magnetique. Kugira ngo babone ubushishozi ku myitwarire yagaragaye mu bushakashatsi, abashakashatsi babaze imiterere ya band ya Moir ya “Magic Angle” igoretse igikoresho cya graphene ya bilayeri ikoresheje icyitegererezo cya Bistritzer-MacDonald kandi inoze ibipimo. Ugereranije no kubara kwambere kwinguni ya "Magic Angle", ingufu nke zibarwa Moire band ntizitandukanijwe numuyoboro mwinshi. Nubwo impinduramatwara igikoresho ari ntoya kuruta inguni ya "magic angle" ibarwa ahandi, igikoresho gifite ibintu bifitanye isano cyane nubushakashatsi bwabanje (Mort insulation na superconductivity), abahanga mu bya fiziki basanze bitunguranye kandi bishoboka.
Nyuma yo gusuzuma neza imyitwarire yubucucike bunini (umubare wibihugu biboneka kuri buri mbaraga), ibiranga abahanga mu bya siyansi byatewe n’ibihugu bishya bivuka bifitanye isano. Mu bihe biri imbere, hazakorwa ubushakashatsi burambuye ku bucucike bw’ibihugu (DOS) kugira ngo hamenyekane imiterere idasanzwe y’imyororokere no kumenya niba bishobora gushyirwa mu rwego rw’amazi ya kwant. Muri ubu buryo, abahanga mu bya siyansi babonye ibintu birenze urugero hafi ya Mox imeze nka insulasiyo mu gikoresho cya graphene ya bilayeri igoramye ifite inguni ntoya (0,93 °). Ubu bushakashatsi bwerekana ko no ku nguni ntoya n'ubucucike buri hejuru, ingaruka zifitanye isano na electron ku miterere ya moiré ni imwe. Mu bihe biri imbere, hazengurutswe ibibaya bya spin byo mu cyiciro cya insulasiyo, kandi icyiciro gishya kirenze urugero kizigwa ku bushyuhe buke. Ubushakashatsi bw'igeragezwa buzahuzwa n'imbaraga zo gusobanukirwa inkomoko y'iyi myitwarire.
Igihe cyo kohereza: Ukwakira-08-2019