Halayyar ratsi na Mohr da bel ɗin lebur a kimiyyar kimiyya da kimiyyar lissafi mai suna "Magic Angle" mai siffar bilayer graphene (TBLG) ta jawo hankalin masana kimiyya sosai, kodayake kaddarorin da yawa suna fuskantar muhawara mai zafi. A cikin wani sabon bincike da aka buga a mujallar Science Progress, Emilio Colledo da masana kimiyya a Sashen Kimiyyar Lissafi da Kayan Aiki a Amurka da Japan sun lura da yadda ake amfani da su wajen sarrafa wutar lantarki da kuma kwatantawa a cikin graphene mai siffar bilayer ...
Wannan binciken ya samar da tarin sabbin bayanai don fahimtar ƙarfin yanayin kwantum a cikin graphene mai lanƙwasa don amfani a cikin kimiyyar lissafi na kwantum. Masana kimiyyar lissafi sun bayyana "Twistronics" a matsayin kusurwar jujjuyawar dangi tsakanin layukan van der Waals da ke kusa don samar da madaurin moiré da lebur a cikin graphene. Wannan ra'ayi ya zama sabuwar hanya ta musamman don canzawa da keɓance halayen na'urori bisa ga kayan girma biyu don cimma kwararar yanzu. An nuna tasirin ban mamaki na "Twistronics" a cikin aikin farko na masu binciken, yana nuna cewa lokacin da aka tara layukan graphene guda biyu a kusurwar jujjuyawar "kusurwar sihiri" ta θ=1.1±0.1°, wani madaurin faɗi mai faɗi ya bayyana. .
A cikin wannan binciken, a cikin graphene mai lanƙwasa (TBLG), an cika matakin rufewa na farko na microstrip (siffar tsari) na superlattice a "kusurwar sihiri" rabin-cika. Ƙungiyar binciken ta gano cewa wannan insulator ne na Mott (insulator mai halayen superconducting) wanda ke nuna superconductivity a matakan doping kaɗan mafi girma da ƙasa. Zane-zanen mataki yana nuna babban superconductor mai zafi tsakanin zafin canjin superconducting (Tc) da zafin Fermi (Tf). Wannan binciken ya haifar da babban sha'awa da muhawara ta ka'ida kan tsarin graphene band, topology da ƙarin tsarin semiconductor na "Magic Angle". Idan aka kwatanta da rahoton ka'idar asali, binciken gwaji ba kasafai yake ba kuma ya fara. A cikin wannan binciken, ƙungiyar ta gudanar da ma'aunin watsawa akan graphene mai lanƙwasa "kusurwar sihiri" wanda ke nuna yanayin rufewa da superconducting masu dacewa.
Kusurwar da ba zato ba tsammani ta karkace ta 0.93 ± 0.01, wadda ta fi ƙanƙanta da kashi 15% fiye da "Magic Angle", ita ce mafi ƙanƙanta da aka ruwaito zuwa yanzu kuma tana nuna halayen superconductor. Waɗannan sakamakon sun nuna cewa sabon yanayin haɗin gwiwa na iya bayyana a cikin graphene mai jujjuyawar bilayer "Magic Angle", ƙasa da babban "kusurwar sihiri", bayan ƙaramin microstrip na graphene na farko. Don gina waɗannan na'urorin graphene mai jujjuyawar bilayer "magic ƙaho", ƙungiyar ta yi amfani da hanyar "tsagewa da tarawa". Tsarin da ke tsakanin layukan boron nitride (BN) mai hexagonal an lulluɓe shi; an tsara shi cikin tsarin sandar Hall tare da wayoyi da yawa da aka haɗa da haɗin Cr/Au (chromium/gold). An ƙera dukkan na'urar graphene mai jujjuyawar bilayer "Magic Angle" a saman layin graphene da aka yi amfani da shi azaman ƙofar baya.
Masana kimiyya suna amfani da dabarun kulle wutar lantarki ta kai tsaye (DC) da kuma hanyoyin kulle wutar lantarki ta alternating (AC) don auna na'urori a cikin na'urorin HE4 da HE3 da aka yi amfani da su wajen famfo. Ƙungiyar ta yi rikodin alaƙar da ke tsakanin juriyar na'urar (Rxx) da kewayon ƙarfin wutar lantarki mai tsawo (VG) kuma ta ƙididdige filin maganadisu na B a zafin jiki na 1.7K. An lura cewa ƙaramin rashin daidaituwar ramin electron-hole ya zama mallakar na'urar graphene mai jujjuyawar bilayer "Magic Angle". Kamar yadda aka lura a cikin rahotannin da suka gabata, ƙungiyar ta yi rikodin waɗannan sakamakon kuma ta yi cikakken bayani game da rahotannin da suka kasance masu ƙarfin iko zuwa yanzu. "Magic Angle" mai halayyar ta karkatar da mafi ƙarancin kusurwar juyawa na na'urar graphene mai bilayer. Tare da yin nazari sosai kan jadawalin fan na Landau, masu binciken sun sami wasu fasaloli masu mahimmanci.
Misali, kololuwar da aka samu a rabin cikawa da kuma lalacewar matakin Landau sau biyu sun yi daidai da yanayin kariya kamar na Moment-like insulation da aka gani a baya. Tawagar ta nuna raguwar daidaiton kusan kwarin juyawa SU(4) da kuma samar da sabon saman Fermi mai siffar quasi-barbashi. Duk da haka, cikakkun bayanai suna buƙatar ƙarin bincike. An kuma lura da bayyanar superconductivity, wanda ya ƙara Rxx (juriya ta tsayi), kamar yadda aka yi a baya. Daga nan sai ƙungiyar ta binciki zafin jiki mai mahimmanci (Tc) na matakin superconducting. Tunda ba a sami wani bayani don ingantaccen doping na superconductors a cikin wannan samfurin ba, masana kimiyya sun ɗauka cewa zafin jiki mai mahimmanci har zuwa 0.5K. Duk da haka, waɗannan na'urori ba su da tasiri har sai sun sami bayanai bayyanannu daga yanayin superconducting. Don ƙarin bincike kan yanayin superconducting, masu binciken sun auna halayen voltage-current huɗu (VI) na na'urar a yawan masu ɗaukar kaya daban-daban.
Juriyar da aka samu ta nuna cewa ana lura da ƙarfin lantarki mai ƙarfi a kan babban kewayon yawan lantarki kuma yana nuna danne ƙarfin lantarki mai ƙarfi lokacin da aka yi amfani da filin maganadisu mai layi ɗaya. Don samun fahimtar halayen da aka lura a cikin binciken, masu binciken sun ƙididdige tsarin Moir band na na'urar graphene mai jujjuyawar "Magic Angle" ta amfani da samfurin Bistritzer-MacDonald da ingantattun sigogi. Idan aka kwatanta da lissafin da ya gabata na kusurwar "Magic Angle", ba a ware ƙaramin ƙarfin lantarki da aka ƙididdige ba daga babban ƙarfin lantarki. Kodayake kusurwar juyawa ta na'urar ta fi ƙanƙanta fiye da kusurwar "magic angle" da aka ƙididdige a wani wuri, na'urar tana da wani abu da ke da alaƙa da binciken da ya gabata (Mort insulation da superconductivity), wanda masana kimiyyar lissafi suka gano cewa ba zato ba tsammani kuma mai yiwuwa ne.
Bayan ƙarin kimanta ɗabi'ar da ke cikin manyan yawa (adadin yanayin da ake da shi akan kowane makamashi), halayen da masana kimiyya suka lura an danganta su da sabbin yanayin kariya da ke da alaƙa da su. A nan gaba, za a gudanar da cikakken bincike kan yawan yanayi (DOS) don fahimtar yanayin kariya da kuma tantance ko za a iya rarraba su a matsayin ruwa mai juyawa na quantum. Ta wannan hanyar, masana kimiyya sun lura da yanayin kariya kusa da yanayin kariya na Mox a cikin na'urar graphene mai jujjuyawa tare da ƙaramin kusurwar juyawa (0.93°). Wannan binciken ya nuna cewa ko da a irin waɗannan ƙananan kusurwoyi da yawan yawa, tasirin haɗin lantarki akan halayen moiré iri ɗaya ne. A nan gaba, za a yi nazarin kwarin juyawa na matakin kariya, kuma za a yi nazarin sabon matakin kariya a ƙaramin zafin jiki. Za a haɗa binciken gwaji tare da ƙoƙarin ka'idoji don fahimtar asalin wannan ɗabi'ar.
Lokacin Saƙo: Oktoba-08-2019