ʻO ke ʻano o nā kāʻei Mohr a me nā kāʻei palahalaha i ka ʻepekema o ka ʻepekema a me ka quantum physics i kapa ʻia ʻo "Magic Angle" twisted bilayer graphene (TBLG) ua hoihoi nui i ka poʻe ʻepekema, ʻoiai he nui nā waiwai e kū nei i ka hoʻopaʻapaʻa wela. I loko o kahi noiʻi hou i paʻi ʻia ma ka puke pai Science Progress, ua ʻike ʻo Emilio Colledo a me nā ʻepekema i ka Department of Physics and Materials Science ma ʻAmelika Hui Pū ʻIa a me Iapana i ka superconductivity a me ka hoʻohālikelike i ka graphene bilayer wili. ʻO ka mokuʻāina ʻo Mott insulator kahi kihi wili ma kahi o 0.93 degere. He 15% ka liʻiliʻi o kēia kihi ma mua o ka angle "magic angle" (1.1 °) i helu ʻia ma ka haʻawina mua. Hōʻike kēia haʻawina ʻoi aku ka nui o ka "kiʻi kilokilo" o ka graphene bilayer wili ʻia ma mua o ka mea i manaʻo mua ʻia.
Hāʻawi kēia haʻawina i ka waiwai o ka ʻike hou no ka wehewehe ʻana i ke ʻano kuantum ikaika i ka graphene bilayer wili no nā noi ma ka quantum physics. Wehewehe 'ia e ka physicists "Twistronics" ma ke 'ano o ka huina wili pili ma waena o nā papa van der Waals e pili ana i mea e hana ai i ka moiré a me nā kaula pa'a ma ka graphene. Ua lilo kēia manaʻo i mea hou a kū hoʻokahi no ka hoʻololi nui ʻana a me ka hoʻopilikino ʻana i nā waiwai o ka mīkini e pili ana i nā mea ʻelua-dimensional e hoʻokō ai i ke kahe o kēia manawa. Ua hōʻike ʻia ka hopena kupaianaha o "Twistronics" i ka hana paionia a ka poʻe noiʻi, e hōʻike ana i ka wā e hoʻopaʻa ʻia ai nā ʻāpana graphene ʻelua-layer ma kahi kihi "magic angle" o θ = 1.1±0.1 °, ʻike ʻia kahi pūʻulu palahalaha loa. .
I loko o kēia haʻawina, i loko o ka graphene bilayer wiliwili (TBLG), ua hoʻopiha piha ʻia ka ʻāpana insulating o ka microstrip mua (kahi hiʻohiʻona) o ka superlattice ma ka "magic angle". Ua hoʻoholo ka hui noiʻi he Mott insulator kēia (he insulator me nā waiwai superconducting) e hōʻike ana i ka superconductivity ma kahi kiʻekiʻe iki a haʻahaʻa. Hōʻike ke kiʻikuhi pae i ka superconductor wela kiʻekiʻe ma waena o ka mahana hoʻololi superconducting (Tc) a me ka wela Fermi (Tf). Ua alakaʻi ʻia kēia noiʻi i ka hoihoi nui a me ka hoʻopaʻapaʻa ʻana no ka hoʻokumu ʻana o ka band graphene, topology a me nā ʻōnaehana semiconductor "Magic Angle". Ke hoʻohālikelike ʻia me ka hōʻike manaʻo kumu, ʻaʻole kakaikahi ka noiʻi hoʻokolohua a ua hoʻomaka ʻia. Ma kēia noiʻi ʻana, ua hana ka hui i nā ana hoʻouna ʻana ma ka "magic angle" wiliwili bilayer graphene e hōʻike ana i nā kūlana insulating a me superconducting pili.
ʻO 0.93 ± 0.01 kahi kihi i manaʻo ʻole ʻia, ʻoi aku ka liʻiliʻi ma mua o ka "Magic Angle" i hoʻokumu ʻia, ʻo ia ka mea liʻiliʻi loa i hōʻike ʻia i kēia lā a hōʻike i nā waiwai superconducting. Hōʻike kēia mau hualoaʻa e hiki ke ʻike ʻia ka mokuʻāina hoʻoponopono hou i ka "Magic Angle" wiliwili bilayer graphene, haʻahaʻa ma mua o ka "magic angle" mua, ma waho o ka microstrip mua o ka graphene. No ke kūkulu ʻana i kēia mau mea "kiwi kilokilo" wiliwili bilayer graphene, ua hoʻohana ka hui i kahi ala "haehae a hoʻopaʻa ʻia". Hoʻopili ʻia ka hale ma waena o nā papa hexagonal boron nitride (BN); i hoʻohālikelike ʻia i loko o kahi geometry koʻokoʻo Hall me nā uea he nui i hui pū ʻia me Cr/Au (chromium/gold) pili pili. ʻO ka "Magic Angle" wiliwili bilayer graphene a pau i hana ʻia ma luna o ka papa graphene i hoʻohana ʻia ma ka puka hope.
Hoʻohana ka poʻe ʻepekema i nā ʻenehana laka maʻamau maʻamau (DC) a me ke au hou ʻana (AC) no ke ana ʻana i nā mea hana i nā cryostat HE4 a me HE3 i puhi ʻia. Ua hoʻopaʻa ka hui i ka pilina ma waena o ke kūpaʻa lōʻihi o ka hāmeʻa (Rxx) a me ka laulā puka puka ākea (VG) a helu i ke kahua magnetic B ma kahi mahana o 1.7K. Ua ʻike ʻia ka asymmetry liʻiliʻi electron-hole he waiwai maoli o ka "Magic Angle" wiliwili bilayer graphene. E like me ka mea i ʻike ʻia ma nā hōʻike mua, ua hoʻopaʻa ka hui i kēia mau hopena a kikoʻī i nā hōʻike i superconducting a hiki i kēia manawa. ʻO ka hiʻohiʻona "Magic Angle" e wili i ke kihi torsion liʻiliʻi o ka mea hana graphene bilayer. Me ka nānā pono ʻana i ka palapala kiʻi Landau fan, ua loaʻa i nā mea noiʻi kekahi mau hiʻohiʻona kaulana.
No ka laʻana, ʻo ke kiʻekiʻe ma ka hapalua piha a me ka degeneracy ʻelua o ka pae Landau e kūlike me nā mokuʻāina ʻo Moment-like insulation i ʻike mua ʻia. Ua hōʻike ka hui i ka haʻihaʻi ʻana o ke awāwa milo ma kahi kokoke i SU(4) a me ka hoʻokumu ʻana i kahi ʻili Fermi quasi-particle hou. Eia naʻe, pono nā kikoʻī i ka nānā kikoʻī. Uaʻike pūʻia keʻano o ka superconductivity, i hoʻonui i ka Rxx (longitudinal resistance), e like me nā haʻawina mua. A laila nānā ka hui i ka wela koʻikoʻi (Tc) o ka pae superconducting. No ka mea ʻaʻohe ʻikepili i loaʻa no ka doping maikaʻi loa o nā superconductors i kēia hāpana, ua manaʻo nā ʻepekema i kahi mahana koʻikoʻi a hiki i 0.5K. Eia nō naʻe, lilo kēia mau mea hana i mea ʻole a hiki i ka hiki ke loaʻa i ka ʻikepili maopopo mai ka mokuʻāina superconducting. No ka noiʻi hou ʻana i ka mokuʻāina superconducting, ua ana nā mea noiʻi i nā hiʻohiʻona ʻehā-terminal voltage-current (VI) o ka hāmeʻa ma nā ʻano like ʻole.
Hōʻike ke kūpaʻa i loaʻa i ka ʻike ʻia ʻana o ka super current ma kahi ākea ākea nui a hōʻike i ka hoʻopaʻa ʻana i ka super current ke hoʻohana ʻia kahi māla magnetic parallel. No ka loaʻa ʻana o ka ʻike i ke ʻano i ʻike ʻia i loko o ke aʻo ʻana, ua helu ka poʻe noiʻi i ka ʻōnaehana Moir band o ka "Magic Angle" twisted bilayer graphene device me ka hoʻohana ʻana i ka model Bistritzer-MacDonald a me nā ʻāpana hoʻomaikaʻi. Ke hoʻohālikelike ʻia me ka helu mua ʻana o ka angle "Magic Angle", ʻaʻole i hoʻokaʻawale ʻia ka band Moire haʻahaʻa haʻahaʻa i helu ʻia mai ka pūʻulu ikehu kiʻekiʻe. ʻOiai ʻoi aku ka liʻiliʻi o ke kihi wili o ka hāmeʻa ma mua o ka ʻokiʻoki "magic angle" i helu ʻia ma kahi ʻē aʻe, he ʻano ʻano ko ka hāmeʻa i pili ikaika i nā haʻawina mua (Mort insulation and superconductivity), i ʻike ʻia e nā physicists he mea i manaʻo ʻole ʻia a hiki ke hiki.
Ma hope o ka loiloi hou ʻana i ke ʻano ma nā ʻano nui (ka helu o nā mokuʻāina i loaʻa i kēlā me kēia ikehu), ʻike ʻia nā hiʻohiʻona i ʻike ʻia e ka poʻe ʻepekema i nā mokuʻāina insulation pili hou. I ka wā e hiki mai ana, e alakaʻi ʻia kahi noiʻi kikoʻī o ka density of states (DOS) no ka hoʻomaopopo ʻana i ke kūlana ʻokoʻa o ka insulation a no ka hoʻoholo ʻana inā hiki ke helu ʻia lākou he quantum spin liquids. Ma kēia ʻano, ʻike nā kānaka ʻepekema i ka superconductivity kokoke i ka mokuʻāina insulating like me Mox i loko o kahi mea graphene bilayer wiliwili me kahi kihi wili liʻiliʻi (0.93°). Hōʻike kēia haʻawina ʻoiai ma nā kihi liʻiliʻi a me nā kiʻekiʻe kiʻekiʻe, ua like ka hopena o ka hoʻopili electron i nā waiwai o ka moiré. I ka wā e hiki mai ana, e aʻo ʻia nā awāwa wili o ka pae insulating, a e aʻo ʻia kahi hana superconducting hou ma kahi haʻahaʻa haʻahaʻa. E hui pū ʻia ka noiʻi hoʻokolohua me nā hoʻāʻo ʻepekema e hoʻomaopopo i ke kumu o kēia ʻano.
Ka manawa kau: Oct-08-2019