Halin ratsi na Mohr da bel ɗin lebur a cikin ilimin kimiyyar kimiyyar kimiyya da ƙididdiga masu yawa da ake kira "Magic Angle" Twisted bilayer graphene (TBLG) ya jawo hankalin masana kimiyya sosai, kodayake yawancin kaddarorin suna fuskantar zazzafar muhawara. A cikin wani sabon binciken da aka buga a mujallar Kimiyya Ci gaban, Emilio Colledo da masana kimiyya a Sashen Physics da Materials Science a Amurka da Japan sun lura superconductivity da kwatance a cikin Twisted bilayer graphene. Jihar Mott insulator tana da madaidaicin kusurwa kusan digiri 0.93. Wannan kusurwar ita ce 15% karami fiye da "kusurwar sihiri" (1.1°) da aka lissafta a cikin binciken da ya gabata. Wannan binciken ya nuna cewa "kusurwar sihiri" na graphene mai juyayi ya fi girma fiye da yadda ake tsammani a baya.
Wannan binciken yana ba da ɗimbin sabbin bayanai don tantance ƙaƙƙarfan abubuwan ban mamaki a cikin graphene mai murɗaɗɗen bilayer don aikace-aikace a cikin kimiyar lissafi. Masana kimiyya sun ayyana "Twistronics" a matsayin kusurwar dangi mai karkatar da ke tsakanin yaduddukan van der Waals na kusa don samar da moire da lebur a cikin graphene. Wannan ra'ayi ya zama sabuwar hanya ta musamman don canzawa sosai da daidaita kaddarorin na'ura bisa ga abubuwa masu girma biyu don cimma kwararar halin yanzu. An kwatanta sakamako mai ban mamaki na "Twistronics" a cikin aikin majagaba na masu bincike, yana nuna cewa lokacin da aka tattara nau'i-nau'i guda biyu na graphene a wani kusurwar "magic angle" na θ = 1.1 ± 0.1 °, bandeji mai laushi ya bayyana. .
A cikin wannan binciken, a cikin jujjuyawar bilayer graphene (TBLG), lokacin insulating na farkon microstrip (siffar tsarin) na superlatice a “kusurwar sihiri” ya cika. Ƙungiyar binciken ta ƙaddamar da cewa wannan Mott insulator ne (mai rufi tare da manyan kaddarorin) wanda ke nuna ƙarfin hali a ƙananan matakan doping. Zane-zanen lokaci yana nuna babban mai sarrafa zafin jiki tsakanin ma'aunin zafin jiki mai ƙarfi (Tc) da zafin Fermi (Tf). Wannan binciken ya haifar da babban sha'awa da muhawarar ka'idar akan tsarin graphene band, topology da ƙarin tsarin semiconductor "Magic Angle". Idan aka kwatanta da ainihin rahoton ka'idar, binciken gwaji ba kasafai ba ne kuma yanzu ya fara. A cikin wannan binciken, ƙungiyar ta gudanar da ma'auni na watsawa a kan "magin sihiri" karkatacciyar bilayer graphene yana nuna matakan da suka dace da insulating da superconducting jihohi.
Kwangilar da ba zato ba tsammani na 0.93 ± 0.01, wanda shine 15% karami fiye da kafa "Magic Angle", kuma shine mafi ƙanƙanci da aka ruwaito har zuwa yau kuma yana nuna kaddarorin masu girma. Waɗannan sakamakon suna nuna cewa sabon yanayin daidaitawa zai iya bayyana a cikin "Magic Angle" karkatacciyar bilayer graphene, ƙasa da "kusurwar sihiri", fiye da farkon microstrip na graphene. Don gina waɗannan na'urori masu jujjuyawar bilayer graphene "ƙahon sihiri", ƙungiyar ta yi amfani da hanyar "yaga da tari". Tsarin da ke tsakanin yaduddukan boron nitride hexagonal (BN) an lullube shi; ƙirƙira a cikin lissafin sandar Hall tare da wayoyi da yawa haɗe zuwa lambobin Cr/Au (chromium/gold). Dukkanin na'urar "Magic Angle" mai murdadden na'urar graphene an ƙera shi a saman Layer na graphene da aka yi amfani da shi azaman ƙofar baya.
Masanan kimiyya suna amfani da daidaitattun halin yanzu kai tsaye (DC) da dabarun kullewa na yanzu (AC) don auna na'urori a cikin famfo HE4 da HE3 cryostats. Tawagar ta yi rikodin alaƙar da ke tsakanin juriya na tsayin na'urar (Rxx) da kewayon ƙarfin ƙarfin ƙofar (VG) da kuma ƙididdige filin maganadisu B a zazzabi na 1.7K. An lura da ƙananan asymmetry-rami na lantarki a matsayin ainihin mallakar na'urar graphene "Magic Angle". Kamar yadda aka gani a cikin rahotannin da suka gabata, ƙungiyar ta rubuta waɗannan sakamakon tare da yin cikakken bayani game da rahotannin da ke kan gaba. Siffar “Angle Magic” tana karkatar da ƙaramin kusurwar torsion na na'urar graphene bilayer. Tare da bincika taswirar fan na Landau, masu binciken sun sami wasu fitattun siffofi.
Misali, kololuwar cika rabin cika da ɓatawar matakin Landau ninki biyu sun yi daidai da jihohin da aka lura a baya-kamar lokacin rufewa. Tawagar ta nuna hutu a cikin ma'auni na kwarin kwarin SU(4) da kuma samuwar wani sabon fili-barbashi na Fermi. Koyaya, cikakkun bayanai suna buƙatar ƙarin cikakken dubawa. An kuma lura da bayyanar superconductivity, wanda ya karu Rxx (juriya na tsayi), kama da binciken da ya gabata. Daga nan sai ƙungiyar ta yi nazarin yanayin zafin jiki mai mahimmanci (Tc) na babban lokaci. Tun da ba a sami bayanai don ingantaccen doping na superconductors a cikin wannan samfurin ba, masana kimiyya sun ɗauka matsanancin zafin jiki har zuwa 0.5K. Duk da haka, waɗannan na'urori suna zama marasa amfani har sai sun sami damar samun cikakkun bayanai daga yanayin da ya dace. Don ci gaba da yin bincike game da yanayin da ya fi ƙarfin aiki, masu binciken sun auna halayen ƙarfin lantarki-na yanzu (VI) huɗu na na'urar a nau'ikan jigilar kaya daban-daban.
Juriya da aka samu yana nuna cewa ana lura da super current a kan mafi girman kewayon yawa kuma yana nuna danne super current lokacin da aka yi amfani da filin maganadisu na daidaici. Don samun fahimtar halin da aka gani a cikin binciken, masu binciken sun ƙididdige tsarin tsarin Moir na "Magic Angle" na'urar graphene mai juyayi ta hanyar amfani da samfurin Bistritzer-MacDonald da ingantattun sigogi. Idan aka kwatanta da lissafin da ya gabata na kusurwar "Magic Angle", ƙididdige ƙananan ƙarfin Moire band ɗin ba ya keɓanta da babban rukunin makamashi. Duk da cewa kusurwar na'urar tana da ƙasa da kusurwar "magic angle" da aka ƙidaya a wani wuri, na'urar tana da wani al'amari mai mahimmanci da ke da alaka da binciken da aka yi a baya (Mort insulation and superconductivity), wanda masana kimiyya suka gano cewa ba zato ba tsammani kuma mai yiwuwa.
Bayan ƙarin kimanta halayen a manyan yawa (yawan jihohin da ke akwai akan kowane makamashi), halayen da masana kimiyya suka lura ana danganta su ga sabbin jahohin rufewa masu alaƙa. A nan gaba, za a gudanar da ƙarin cikakken bincike game da yawan jihohin (DOS) don fahimtar yanayin yanayin rufewa da sanin ko za a iya rarraba su azaman kididdigar ruwa. Ta wannan hanyar, masana kimiyya sun lura da haɓakawa kusa da yanayin insulating na Mox-kamar a cikin na'ura mai jujjuyawar bilayer graphene tare da ƙaramin kusurwa (0.93°). Wannan binciken ya nuna cewa ko da a irin waɗannan ƙananan kusurwoyi da manyan yawa, tasirin haɗin gwiwar lantarki akan kaddarorin moiré iri ɗaya ne. A nan gaba, za a yi nazarin ƙwarin ƙwanƙwasa na yanayin insulating, kuma za a yi nazarin wani sabon lokaci mai ƙarfi a ƙananan zafin jiki. Za a haɗa bincike na gwaji tare da ƙoƙarin fahimtar tushen wannan hali.
Lokacin aikawa: Oktoba-08-2019