Maitiro eMohr mitsetse uye mabhandi akafuratira musainzi yesainzi uye quantum fizikisi inonzi "Magic Angle" yakamonyoroka bilayer graphene (TBLG) yakwezva kufarira kukuru kubva kumasaenzi, kunyangwe zvivakwa zvakawanda zvakatarisana negakava rinopisa. Muchidzidzo chitsva chakaburitswa mujenari Science Progress, Emilio Colledo uye masayendisiti muDhipatimendi reFizikisi uye Zvishandiso Sainzi muUnited States neJapan vakacherekedza superconductivity uye kuenzanisa mune yakamonyoroka bilayer graphene. Iyo Mott insulator state ine twist angle inosvika 0.93 madhigirii. Iyi kona idiki 15% pane "magic angle" angle (1.1 °) yakaverengerwa muchidzidzo chakapfuura. Ichi chidzidzo chinoratidza kuti "magic angle" huwandu hweakamonyoroka bilayer graphene yakakura kupfuura yaimbotarisirwa.
Chidzidzo ichi chinopa hupfumi hweruzivo rutsva rwekududzira iyo yakasimba quantum phenomena mu yakamonyoroka bilayer graphene yekushandisa mu quantum physics. Nyanzvi dzefizikisi dzinotsanangura "Twistronics" seyakamonyoroka kona iri pakati pezvikamu zvakatarisana nevan der Waals kugadzira moiré uye mabhendi akati sandara mugraphene. Iyi pfungwa yave nzira nyowani uye yakasarudzika yekuchinja zvakanyanya uye kugadzirisa zvivakwa zvemudziyo zvichibva pane maviri-dimensional zvinhu kuti uwane kuyerera kwazvino. Mhedzisiro inoshamisa ye "Twistronics" yakaenzanisirwa mubasa rekutanga revatsvakurudzi, zvichiratidza kuti kana maviri-layer graphene layers akaturikidzana pa "magic angle" twist angle ye θ=1.1±0.1 °, bhendi rakati sandarara rinoonekwa. .
Muchidzidzo ichi, mune yakamonyoroka bilayer graphene (TBLG), iyo insulating chikamu cheyokutanga microstrip (chimiro chechimiro) che superlattice pa "magic angle" yakazadzwa semi-yakazadzwa. Chikwata chekutsvagisa chakaona kuti iyi iMott insulator (insulator ine superconducting zvivakwa) inoratidza superconductivity padanho repamusoro uye rakaderera doping. Iyo chikamu dhizaini inoratidza yakanyanya tembiricha superconductor pakati peiyo superconducting shanduko yekushisa (Tc) uye tembiricha yeFermi (Tf). Tsvagiridzo iyi yakatungamira mukufarira kukuru uye gakava redzidziso pane graphene bhendi chimiro, topology uye yekuwedzera "Magic Angle" semiconductor masisitimu. Kana ichienzaniswa neyekutanga theoretical report, ongororo yekuyedza haiwanzo uye ichangotanga. Muchidzidzo ichi, timu yakaita zviyero zvekutapurirana pa "magic angle" yakamonyoroka bilayer graphene inoratidza yakakodzera insulating uye superconducting nyika.
Iyo isingatarisirwe yakakanganiswa angle ye0.93 ± 0.01, iri 15% idiki pane yakagadzwa "Magic Angle", ndiyo idiki yakambotaurwa kusvika parizvino uye inoratidza superconducting zvivakwa. Mhedzisiro iyi inoratidza kuti mamiriro matsva ekubatanidza anogona kuoneka mu "Magic Angle" yakamonyoroka bilayer graphene, yakaderera pane yekutanga "magic angle", kupfuura yekutanga microstrip yegraphene. Kuvaka idzi "nyanga dzemashiripiti" dzakamonyoroka bilayer graphene zvishandiso, timu yakashandisa nzira ye "kubvarura uye stack". Chimiro chiri pakati pehexagonal boron nitride (BN) layers yakavharwa; yakarongedzwa muHall rod geometry ine waya dzakawanda dzakabatanidzwa kune Cr/Au (chromium/goridhe) epamucheto. Iyo yese "Magic Angle" yakamonyoroka bilayer graphene mudziyo wakagadzirwa pamusoro peiyo graphene layer inoshandiswa segedhi rekumashure.
Masayendisiti anoshandisa yakajairwa yakananga ikozvino (DC) uye alternating ikozvino (AC) yekuvhara maitiro kuyera midziyo mupombi HE4 uye HE3 cryostats. Chikwata chakarekodha hukama pakati pechigadzirwa chelongitudinal kuramba (Rxx) uye yakawedzera gedhi voltage (VG) renji uye yakaverengera iyo magineti B patembiricha ye1.7K. Diki erekitironi-gomba asymmetry yakaonekwa sechinhu chekuzvarwa che "Magic Angle" yakamonyoroka bilayer graphene mudziyo. Sezvakacherechedzwa mumishumo yapfuura, timu yakanyora izvi mhedzisiro uye yakatsanangura mishumo yanga ichiita mashura kusvika parizvino. Hunhu "Magic Angle" inomonyorora iyo shoma torsion angle yebilayer graphene mudziyo. Nekunyatsoongorora kweLandau fan chati, vaongorori vakawana zvimwe zvinozivikanwa.
Semuenzaniso, iyo peak pahafu yekuzadza uye kupetwa kaviri kuderera kweLandau level inopindirana neyakacherechedzwa Moment-like insulation states. Chikwata chakaratidza kuzorora mukuenzanirana kweinenge spin mupata SU (4) uye kuumbwa kweiyo itsva quasi-particle Fermi pamusoro. Nekudaro, iwo maficha anoda kuongororwa kwakadzama. Kuonekwa kwe superconductivity kwakaonekwawo, iyo yakawedzera Rxx (longitudinal resistance), yakafanana nezvidzidzo zvekare. Chikwata chakabva chaongorora tembiricha yakakosha (Tc) yechikamu che superconducting. Sezvo pasina data yakawanikwa yeakanyanya doping yema superconductors mune iyi sampuli, masayendisiti akafungidzira tembiricha yakaoma inosvika 0.5K. Nekudaro, zvishandiso izvi hazvishande kusvika vakwanisa kuwana data rakajeka kubva kune superconducting state. Kuenderera mberi nekuongorora iyo superconducting mamiriro, vaongorori vakayera iwo mana-terminal voltage-ikozvino (VI) maitiro emudziyo pane akasiyana densities.
Kupokana kwakawanikwa kunoratidza kuti super ikozvino inocherechedzwa pamusoro pehombe density renji uye inoratidza kudzvanywa kweiyo super ikozvino kana parallel magineti yaiswa. Kuti uwane nzwisiso yemaitiro akaonekwa muchidzidzo, vaongorori vakaverenga Moir bhendi chimiro che "Magic Angle" yakamonyoroka bilayer graphene mudziyo vachishandisa Bistritzer-MacDonald modhi uye yakagadziridzwa paramita. Kuenzaniswa neyekare kuverenga kwe "Magic Angle" angle, iyo yakaverengerwa yakaderera simba Moire bhendi haina kuparadzaniswa kubva kune yakakwirira simba bhendi. Kunyange zvazvo kona yemuchina iri idiki pane “magic angle” yakaverengerwa kumwe kunhu, mudziyo une chiitiko chine hukama zvakanyanya nezvidzidzo zvakapfuura (Mort insulation uye superconductivity), zvakaonekwa nenyanzvi zvisingatarisirwi uye zvinogoneka.
Mushure mekuongororazve hunhu pahukuru hukuru (huwandu hwematunhu anowanikwa pasimba rega rega), hunhu hunocherechedzwa nemasainzi hunonzi hunobva kune huchangobva kubuda hwakabatana hwekusunga. Mune ramangwana, ongororo yakadzama yedensity yematunhu (DOS) ichaitwa kuti unzwisise iyo isinganzwisisike mamiriro ekudzivirira uye kuona kana ichigona kurongwa se quantum spin zvinwiwa. Nenzira iyi, masayendisiti akaona superconductivity padyo neMox-yakafanana insulating state mune yakamonyoroka yebilayer graphene mudziyo ine diki twist angle (0.93 °). Ichi chidzidzo chinoratidza kuti kunyangwe pamakona madiki akadai uye dhizaini yakakwira, mhedzisiro yeelectron correlation pazvinhu zve moiré yakafanana. Mune ramangwana, mipata inotenderera yechikamu chekudzivirira ichadzidzwa, uye chikamu chitsva che superconducting chichadzidzwa pane tembiricha yakaderera. Tsvagiridzo yekuyedza inosanganiswa nekuedza kwe theoretical kuti unzwisise kwakabva maitiro aya.
Nguva yekutumira: Oct-08-2019