Makhalidwe a mikwingwirima ya Mohr ndi malamba athyathyathya mu sayansi ya sayansi ndi quantum physics yotchedwa "Magic Angle" yopotoka bilayer graphene (TBLG) yakopa chidwi chachikulu kuchokera kwa asayansi, ngakhale kuti katundu wambiri amakumana ndi mkangano waukulu. Mu kafukufuku watsopano wofalitsidwa mu nyuzipepala Science Progress, Emilio Colledo ndi asayansi mu Dipatimenti ya Physics ndi Materials Science ku United States ndi Japan anaona superconductivity ndi fanizo lopotoka bilayer graphene. Boma la insulator la Mott lili ndi ngodya yopotoka pafupifupi madigiri 0.93. Ngolo iyi ndi yaying'ono ndi 15% kuposa "magic angle" (1.1 °) yowerengedwa m'kafukufuku wapita. Kafukufukuyu akuwonetsa kuti "magic angle" osiyanasiyana opotoka bilayer graphene ndi okulirapo kuposa momwe amayembekezera.
Kafukufukuyu akupereka zambiri zatsopano zowunikira zochitika zamphamvu za quantum mu opotoka bilayer graphene pazogwiritsidwa ntchito mu quantum physics. Akatswiri a sayansi ya zakuthambo amatanthauzira "Twistronics" ngati ngodya yokhotakhota pakati pa zigawo zoyandikana za van der Waals kuti apange ma moiré ndi ma bandi osalala mu graphene. Lingaliro ili lakhala njira yatsopano komanso yapadera yosinthira kwambiri ndikusintha mawonekedwe a chipangizocho potengera zida zamitundu iwiri kuti akwaniritse kuyenda kwapano. Zotsatira zochititsa chidwi za "Twistronics" zinawonetsedwa mu ntchito yochita upainiya ya ochita kafukufuku, kusonyeza kuti pamene zigawo ziwiri za graphene zosanjikiza zimayikidwa pa "magic angle" yopindika ya θ = 1.1 ± 0.1 °, gulu lathyathyathya kwambiri likuwonekera. .
Mu phunziro ili, mu zopotoka bilayer graphene (TBLG), ndi insulating gawo la woyamba microstrip (structural Mbali) wa superlattice pa "magic angle" anali theka-odzazidwa. Gulu lofufuzalo lidatsimikiza kuti iyi ndi insulator ya Mott (insulator yokhala ndi superconducting properties) yomwe imawonetsa superconductivity pamlingo wokwera pang'ono komanso wotsika kwambiri wa doping. Chithunzi cha gawo chikuwonetsa kutentha kwapamwamba kwambiri pakati pa kutentha kwapamwamba kwambiri (Tc) ndi kutentha kwa Fermi (Tf). Kafukufukuyu adadzetsa chidwi chachikulu komanso mkangano wazongopeka pamapangidwe a gulu la graphene, topology ndi machitidwe owonjezera a "Magic Angle" semiconductor. Poyerekeza ndi lipoti loyambirira lanthanthi, kafukufuku woyesera ndi wosowa ndipo wangoyamba kumene. Mu kafukufukuyu, gululo lidachita zoyezera zopatsirana pa "magic angle" yopindika bilayer graphene kuwonetsa madera otetezedwa ndi ma superconducting.
Mbali yolakwika mosayembekezereka ya 0.93 ± 0.01, yomwe ndi yaying'ono ndi 15% kuposa "Magic Angle" yomwe idakhazikitsidwa, ndiyonso yaying'ono kwambiri yomwe idanenedwapo mpaka pano ndipo ikuwonetsa katundu wapamwamba kwambiri. Zotsatira izi zikusonyeza kuti latsopano malumikizanidwe boma akhoza kuonekera mu "Magic Angle" wokhotakhota bilayer graphene, m'munsi kuposa chachikulu "matsenga ngodya", kupitirira woyamba microstrip wa graphene. Kuti apange zida za "nyanga zamatsenga" zopotoka za bilayer graphene, gululo lidagwiritsa ntchito njira ya "kung'amba ndi kuwundana". Mapangidwe apakati pa zigawo za hexagonal boron nitride (BN) amatsekedwa; yojambulidwa mu Hall rod geometry yokhala ndi mawaya angapo ophatikizidwa ndi Cr/Au (chromium/golide) m'mphepete. Chida chonse cha "Magic Angle" chopotoka cha bilayer graphene chinapangidwa pamwamba pa graphene wosanjikiza wogwiritsidwa ntchito ngati chipata chakumbuyo.
Asayansi amagwiritsa ntchito njira zotsekera zachindunji (DC) ndi njira zotsekera zapano (AC) kuyeza zida zomwe zili mu ma cryostats opopa a HE4 ndi HE3. Gululo linajambula ubale wapakati pa kukana kwautali wa chipangizocho (Rxx) ndi voteji yowonjezereka (VG) ndikuwerengera mphamvu ya maginito B pa kutentha kwa 1.7K. Asymmetry yaing'ono ya electron-hole inawonedwa kuti ndi katundu wachilengedwe wa chipangizo cha "Magic Angle" chopotoka cha bilayer graphene. Monga tawonera m'ma malipoti am'mbuyomu, gululo lidalemba zotsatirazi ndikulongosola mwatsatanetsatane malipoti omwe akhala akuchita bwino kwambiri mpaka pano. Makhalidwe a "Magic Angle" amapotoza mbali yocheperako ya chipangizo cha bilayer graphene. Poyang'anitsitsa tchati cha fan la Landau, ofufuzawo adapeza zinthu zina zodziwika bwino.
Mwachitsanzo, nsonga ya kudzaza theka ndi kuwonongeka kawiri kwa mulingo wa Landau zimagwirizana ndi zomwe zidawonedwa kale za Moment-like insulation. Gulu anasonyeza yopuma mu symmetry wa pafupifupi sapota chigwa SU (4) ndi mapangidwe latsopano quasi-tinthu Fermi pamwamba. Komabe, mwatsatanetsatane amafuna kuunikanso mwatsatanetsatane. Mawonekedwe a superconductivity adawonedwanso, omwe adachulukitsa Rxx (kukana kwakutali), ofanana ndi maphunziro am'mbuyomu. Gululo linayang'ana kutentha kwakukulu (Tc) kwa gawo la superconducting. Popeza palibe deta yomwe idapezedwa kuti ipange doping yabwino kwambiri ya superconductors pachitsanzo ichi, asayansiwo adaganiza kuti kutentha kwakukulu mpaka 0.5K. Komabe, zipangizozi zimakhala zosagwira ntchito mpaka zitatha kupeza deta yomveka kuchokera ku superconducting state. Kuti afufuzenso za superconducting state, ofufuzawo anayeza mawonekedwe a voltage-current (VI) a chipangizocho pamakachulukidwe osiyanasiyana onyamula.
Kukaniza komwe kumapezeka kukuwonetsa kuti super current imayang'aniridwa pamlingo wokulirapo ndikuwonetsa kuponderezedwa kwaposachedwa kwambiri pakagwiritsidwa ntchito maginito ofanana. Kuti apeze chidziwitso pamayendedwe omwe adawonedwa mu kafukufukuyu, ofufuzawo adawerengera mawonekedwe a gulu la Moir la "Magic Angle" chida chopotoka cha bilayer graphene pogwiritsa ntchito chitsanzo cha Bistritzer-MacDonald ndikuwongolera magawo. Poyerekeza ndi mawerengedwe am'mbuyomu a "Magic Angle", gulu lowerengera lamphamvu la Moire silinasiyanitsidwe ndi gulu lamphamvu kwambiri. Ngakhale mapindikidwe a chipangizochi ndi ang'onoang'ono kusiyana ndi "magic angle" omwe amawerengedwa kwina, chipangizochi chili ndi zochitika zomwe zimagwirizana kwambiri ndi kafukufuku wam'mbuyomo (Mort insulation and superconductivity), zomwe akatswiri a sayansi adapeza kuti zinali zosayembekezereka komanso zotheka.
Pambuyo powunikanso momwe zimakhalira pakuchulukirachulukira (chiwerengero cha mayiko omwe akupezeka pa mphamvu iliyonse), zomwe asayansi amawona zimatengera zomwe zangotuluka kumene. M'tsogolomu, kafukufuku watsatanetsatane wa density of states (DOS) adzachitidwa kuti amvetsetse momwe kusungirako kumakhalira komanso kudziwa ngati kungagawidwe ngati zakumwa za quantum spin. Mwanjira iyi, asayansi adawona kuti superconductivity pafupi ndi gawo la Mox-monga insulating mu chipangizo chopotoka cha bilayer graphene chokhala ndi ngodya yaying'ono yopindika (0.93 °). Kafukufukuyu akuwonetsa kuti ngakhale pamakona ang'onoang'ono komanso osalimba kwambiri, zotsatira za kulumikizana kwa ma elekitironi pazinthu za moiré ndizofanana. M'tsogolomu, zigwa zozungulira za gawo lotetezera zidzaphunziridwa, ndipo gawo latsopano la superconducting lidzaphunziridwa pa kutentha kochepa. Kafukufuku woyesera adzaphatikizidwa ndi zoyesayesa zamalingaliro kuti amvetsetse chiyambi cha khalidweli.
Nthawi yotumiza: Oct-08-2019