ʻO ke ʻano o nā kaha Mohr a me nā kāʻei pālahalaha i ka ʻepekema o ka ʻepekema a me ka physics quantum i kapa ʻia ʻo "Magic Angle" twisted bilayer graphene (TBLG) ua huki nui i ka hoihoi mai nā kānaka ʻepekema, ʻoiai he nui nā waiwai e kū nei i ka hoʻopaʻapaʻa wela. Ma kahi noiʻi hou i paʻi ʻia ma ka puke pai Science Progress, ua ʻike ʻo Emilio Colledo a me nā kānaka ʻepekema ma ka Department of Physics and Materials Science ma ʻAmelika Hui Pū ʻIa a me Iapana i ka superconductivity a me ka hoʻohālikelike i loko o ka twisted bilayer graphene. Loaʻa i ke kūlana insulator Mott kahi kihi wili ma kahi o 0.93 degere. ʻOi aku ka liʻiliʻi o kēia kihi ma mua o ke kihi "magic angle" (1.1°) i helu ʻia ma ke noiʻi ma mua. Hōʻike kēia noiʻi ua ʻoi aku ka nui o ka laulā "magic angle" o ka twisted bilayer graphene ma mua o ka mea i manaʻo ʻia ma mua.
Hāʻawi kēia haʻawina i ka nui o ka ʻike hou no ka wehewehe ʻana i nā hanana quantum ikaika i loko o ka graphene bilayer i wili ʻia no nā noi i loko o ka physics quantum. Wehewehe nā physicists iā "Twistronics" ʻo ke kihi wili pili ma waena o nā papa van der Waals e pili ana e hana i nā hui moiré a me nā pālahalaha i loko o ka graphene. Ua lilo kēia manaʻo i ʻano hana hou a kū hoʻokahi no ka hoʻololi nui ʻana a me ka hoʻopilikino ʻana i nā waiwai o ka hāmeʻa e pili ana i nā mea ʻelua-dimensional e hoʻokō ai i ke kahe o ke au. Ua hōʻike ʻia ka hopena kupaianaha o "Twistronics" ma ka hana paionia a nā mea noiʻi, e hōʻike ana i ka wā e hoʻopaʻa ʻia ai ʻelua mau papa graphene hoʻokahi papa ma kahi kihi wili "magic angle" o θ=1.1 ± 0.1 °, ʻike ʻia kahi hui pālahalaha loa. .
Ma kēia haʻawina, ma ka graphene twisted bilayer (TBLG), ua piha hapa ka pae insulating o ka microstrip mua (hiʻohiʻona kūkulu) o ka superlattice ma ka "magic angle". Ua hoʻoholo ka hui noiʻi he Mott insulator kēia (kahi insulator me nā waiwai superconducting) e hōʻike ana i ka superconductivity ma nā pae doping kiʻekiʻe iki a me nā pae doping haʻahaʻa. Hōʻike ka kiʻikuhi pae i ka superconductor wela kiʻekiʻe ma waena o ka mahana hoʻololi superconducting (Tc) a me ka mahana Fermi (Tf). Ua alakaʻi kēia noiʻi i ka hoihoi nui a me ka hoʻopaʻapaʻa kumumanaʻo ma ke ʻano o ka hui graphene, ka topology a me nā ʻōnaehana semiconductor "Magic Angle" hou aʻe. Ke hoʻohālikelike ʻia me ka hōʻike kumumanaʻo mua, he kakaikahi ka noiʻi hoʻokolohua a ua hoʻomaka wale. Ma kēia haʻawina, ua hana ka hui i nā ana hoʻoili ma ka graphene twisted bilayer "magic angle" e hōʻike ana i nā kūlana insulating a me superconducting pili.
ʻO kahi kihi i hoʻopilikia ʻole ʻia o 0.93 ± 0.01, ʻo ia hoʻi he 15% ka liʻiliʻi ma mua o ka "Magic Angle" i hoʻokumu ʻia, ʻo ia hoʻi ka mea liʻiliʻi loa i hōʻike ʻia a hiki i kēia lā a hōʻike i nā waiwai superconducting. Hōʻike kēia mau hopena e hiki ke ʻike ʻia ke kūlana pilina hou ma ka graphene bilayer i wili ʻia "Magic Angle", haʻahaʻa ma mua o ka "magic angle" mua, ma ʻō aku o ka microstrip mua o ka graphene. No ke kūkulu ʻana i kēia mau mea hana graphene bilayer i wili ʻia "magic horn", ua hoʻohana ka hui i kahi ala "haehae a hoʻopaʻa". Ua hoʻopili ʻia ke ʻano ma waena o nā papa hexagonal boron nitride (BN); i hoʻohālikelike ʻia i loko o kahi geometry Hall rod me nā uea he nui i hoʻopili ʻia i nā pilina lihi Cr/Au (chromium/gula). Ua hana ʻia ka mea hana graphene bilayer i wili ʻia "Magic Angle" holoʻokoʻa ma luna o ka papa graphene i hoʻohana ʻia ma ke ʻano he puka hope.
Hoʻohana nā kānaka ʻepekema i nā ʻano hana laka pololei (DC) a me ke au ʻokoʻa (AC) e ana i nā mea hana i loko o nā cryostats HE4 a me HE3 i hoʻopaʻa ʻia. Ua hoʻopaʻa ka hui i ka pilina ma waena o ke kū'ē lōʻihi o ka mea hana (Rxx) a me ka laulā voltage puka i hoʻonui ʻia (VG) a ua helu ʻia ke kahua magnetic B ma ka mahana o 1.7K. Ua ʻike ʻia ka asymmetry lua electron liʻiliʻi he waiwai kūlohelohe o ka mea hana graphene bilayer twisted "Magic Angle". E like me ka mea i ʻike ʻia ma nā hōʻike ma mua, ua hoʻopaʻa ka hui i kēia mau hopena a ua hōʻike kikoʻī i nā hōʻike i hoʻokele nui ʻia a hiki i kēia manawa. ʻO ke ʻano "Magic Angle" e wili i ka kihi torsion liʻiliʻi loa o ka mea hana graphene bilayer. Me ka nānā pono ʻana i ka pakuhi peʻahi Landau, ua loaʻa i nā mea noiʻi kekahi mau hiʻohiʻona koʻikoʻi.
No ka laʻana, ʻo ka piko ma ka hapalua hoʻopiha a me ka degeneracy pālua o ka pae Landau e kūlike me nā kūlana insulation Moment-like i ʻike mua ʻia. Ua hōʻike ka hui i kahi haki i ka symmetry o ke awāwa spin kokoke SU(4) a me ka hoʻokumu ʻana o kahi ʻili Fermi quasi-particle hou. Eia nō naʻe, pono nā kikoʻī i kahi nānā kikoʻī. Ua ʻike ʻia hoʻi ke ʻano o ka superconductivity, kahi i hoʻonui ai iā Rxx (kūʻē longitudinal), e like me nā haʻawina mua. A laila ua nānā ka hui i ka mahana koʻikoʻi (Tc) o ka pae superconducting. ʻOiai ʻaʻohe ʻikepili i loaʻa no ka doping kūpono o nā superconductors i kēia laʻana, ua manaʻo nā kānaka ʻepekema i kahi mahana koʻikoʻi a hiki i ka 0.5K. Eia naʻe, lilo kēia mau mea hana i mea ʻole a hiki i ka hiki iā lākou ke loaʻa ka ʻikepili maopopo mai ke kūlana superconducting. No ka noiʻi hou ʻana i ke kūlana superconducting, ua ana nā mea noiʻi i nā ʻano voltage-current ʻehā-terminal (VI) o ka mea hana ma nā densities lawe like ʻole.
Hōʻike ka pale i loaʻa e ʻike ʻia ana ke au nui ma luna o kahi pae density nui a hōʻike i ka hoʻopau ʻana o ke au nui ke hoʻopili ʻia kahi kahua magnetic like. No ka loaʻa ʻana o ka ʻike i ke ʻano i ʻike ʻia ma ke aʻo ʻana, ua helu nā mea noiʻi i ke ʻano o ka hui Moir o ka hāmeʻa graphene twisted bilayer "Magic Angle" me ka hoʻohana ʻana i ke kumu hoʻohālike Bistritzer-MacDonald a me nā palena i hoʻomaikaʻi ʻia. Ke hoʻohālikelike ʻia me ka helu mua o ke kihi "Magic Angle", ʻaʻole i hoʻokaʻawale ʻia ke kāʻei Moire ikehu haʻahaʻa i helu ʻia mai ka hui ikehu kiʻekiʻe. ʻOiai ʻoi aku ka liʻiliʻi o ke kihi wili o ka hāmeʻa ma mua o ke kihi "magic angle" i helu ʻia ma kahi ʻē aʻe, loaʻa i ka hāmeʻa kahi hanana e pili pono ana i nā haʻawina mua (Mort insulation a me superconductivity), kahi i ʻike ʻia e nā physicists he mea i manaʻo ʻole ʻia a hiki ke hana.
Ma hope o ka loiloi hou ʻana i ke ʻano ma nā densities nui (ka helu o nā mokuʻāina i loaʻa ma kēlā me kēia ikehu), ua hoʻopili ʻia nā ʻano i ʻike ʻia e nā ʻepekema i nā mokuʻāina insulation pili hou. I ka wā e hiki mai ana, e hana ʻia kahi noiʻi kikoʻī hou aʻe o ka density of states (DOS) e hoʻomaopopo i ke kūlana ʻē o ka insulation a e hoʻoholo inā hiki ke hoʻokaʻawale ʻia lākou he mau wai spin quantum. Ma kēia ʻano, ua ʻike nā ʻepekema i ka superconductivity kokoke i ke kūlana insulating Mox-like i loko o kahi mea graphene bilayer twisted me kahi kihi twist liʻiliʻi (0.93°). Hōʻike kēia noiʻi ʻoiai ma ia mau kihi liʻiliʻi a me nā densities kiʻekiʻe, ua like ka hopena o ka pilina electron ma nā waiwai o moiré. I ka wā e hiki mai ana, e aʻo ʻia nā awāwa spin o ka pae insulating, a e aʻo ʻia kahi pae superconducting hou ma kahi mahana haʻahaʻa. E hui pū ʻia ka noiʻi hoʻokolohua me nā hana theoretical e hoʻomaopopo i ke kumu o kēia ʻano.
Ka manawa hoʻouna: ʻOkakopa-08-2019