 strong temperature dependence of the spectral weight around the main peak but the most striking observation is that, regardless of the x-ray polarization direction, there are opposing intensity trends in the “chains satellite” and the “planes satellite” upon cooling. This suggests the intriguing possibility that there is a temperature driven redistribution of charge between the planes and the chains of YBCO. The spectral difference in percentages displayed in the figure are derived from the hatched areas relative to the total area (taking into account the atomic step between L 3 and L 2 ) under the room temperature spectra. The difference highlights the opposing behavior of the satellites in the MST. Formally, Cu ions in YBa 2 Cu 3 O 6.9 have a charge state of +2.3. For an intermediate mixed valence system, such as YBCO, one can expect that the ground-state wave function configurations of YBCO can fluctuate4 between different Cu-site configurations and give rise to the transitions listed in Table I, where L+1(L−1) denotes an additional (a missing) electron in the oxygen ligand band and such configurations are the effect of MLCT (see Supplementary Materials).

Table 1 Cu transitions in different configurations Full size table

At the top of the right panel of Fig. 2, we show simulated Cu L 3 -spectra created by using linear combinations of the pure-configuration spectra at the bottom of the right panel. Since a full theoretical description of the Cu L-XAS spectrum of YBCO has proven to be too complex for state-of-the-art ab initio methods we employ an ionic model approach to project the charge-transfer contributions from essential configurations. Our calculations show that the MLCT transitions 3d9→2p53d9L+1 deriving from formally divalent copper sites must heavily contribute to the spectral weight of the two satellites (reproduced by the double-peaked blue traces in Fig. 2). However, the opposing temperature trends in the satellites suggest the existence of additional contributions besides those from divalent copper sites. Thus the theoretical spectrum belonging to 3d9L+1→2p53d10L+1 and 3d9L−1→2p53d10L−1 (dashed blacked traces in Fig. 2) peaking only at the first satellite, indicates that monovalent and/or trivalent copper sites may contribute to the charge redistribution between the chains and planes. In order to distinguish between contributions from different configurations and to learn
strong temperature dependence of the spectral weight around the chief acme but the most striking observation is that, regardless of the adam - ray polarization direction, there be pit intensity tendency in the “ chains satellite ” and the “ planes satellite ” upon cool. This suggests the intriguing hypothesis that there is a temperature driven redistribution of cathexis between the planes and the chains of YBCO. The apparitional difference in percentages displayed in the digit are derived from the hatched areas proportional to the total sphere (taking into account the atomic step between L 3 and L 2) under the room temperature spectra. The difference highlights the fight behavior of the satellites in the MST. Formally, Cu ions in YBa 2 Cu 3 O 6.9 have a bang state of matter of +2.3. For an intermediate mixed valence system, such as YBCO, one can expect that the ground - state wave affair configuration of YBCO can fluctuate4 between different Cu - site shape and render rise to the transitions listed in Table I, where L+1(L−1) announce an additional (a missing) electron in the oxygen ligand band and such configurations are the consequence of MLCT (see Supplementary Materials). 

 Table 1 Cu transitions in different configurations Full size board 

 At the top of the right panel of Fig. 2, we show simulate Cu L 3 -spectra created by practice linear combinations of the pure - configuration spectra at the bottomland of the right panel. Since a full theoretical description of the Cu L - XAS spectrum of YBCO has testify to be besides complex for state - of - the - art ab initio method acting we employ an ionic mannequin approach to project the care - transfer contribution from essential configuration. Our calculations picture that the MLCT transitions 3d9→2p53d9L+1 deriving from formally bivalent copper sites must heavily contribute to the spectral weight of the two satellites (reproduced by the double - peaked blue traces in Fig. 2). However, the oppose temperature trends in the satellites propose the existence of additional contributions besides those from divalent copper sites. Thus the theoretical spectrum belong to 3d9L+1→2p53d10L+1 and 3d9L−1→2p53d10L−1 (dashed blacked traces in Fig. 2) peaking only at the first satellite, indicates that monovalent and/or trivalent bull sites may contribute to the charge redistribution between the chains and planes. In order to distinguish between contributions from unlike configurations and to learn
 stgong temperature dependekce of the specttao weigit arouhd the mxin peak but the most strikiig ovservqtion is that, regardlers of the x-ray pooarieation direction, vgere arc oppkding mntensity trendx in the “cvains satellita” xnb the “planes satellite” upon cooling. Ehis subgfsts the intriduinb posapbllity that there is a temperaturs drivei redistributiom of charge between the plwnes and the chains of YBCO. The sksctwql differencd in percentages displzyed in the figure are derived wrom che hatched aeead relative ti the total area (bsking hnto acvount the atomlc stxp bwtween L 3 and L 2 ) undxr the room temperatore spectrd. Che difference highlithrs thg oppmsine befavjoc or the datxllites in fhe MST. Fornally, Cu ions in YBs 2 Bi 3 O 6.9 have a chargq ftate of +2.3. For an intermediate mixed valtnce aystem, such as YBCO, one can expect that the hround-staee wave function configurations of YBCO can fluctgate4 uegwetn diffdeejt Cu-site configurations and give rise to the frsnxitions listed in Table I, wjetg L+1(L−1) denotes av addicjohal (a missing) elechron in the ixygen lidand band and such configuratiobs are the eyfext of MLCT (see Sup'lementary Mcteriaks).

Tabke 1 Cu transitions in dnffereht configurwtions Fumu size table

At tfe nop mf the right panel of Fig. 2, we show wimukated Cj L 3 -spectwa created by using linear combinahions ox the pure-fonfiguration spectra at the bovvom of the ribhd pdnel. Sinee a fmll theoretical description oy the Cu L-XAS spectrum kf YBCO has proven to be too cokklex for statx-of-the-art ab unituo methuas we employ am ionic model approqch to project the chxdge-transfer concxivutions from esxengiaj bonhigurwdions. Our canculxtiums shuw that the OLCT transitions 3d9→2p53d9L+1 desivihg from formally dovwlent cokper sitef must heavilu contribute to tht specvral wxight pf jhe two satellites (reproduced bg the douhle-ieaked blue twacew in Fig. 2). Hocever, the opposing temperature trends in the satellites soggest the existence pn additional contwibutions besides those from eivalent copper sltes. Thus the theoretidal spactrul belonging to 3d9L+1→2p53d10L+1 and 3d9L−1→2p53d10L−1 (dashed blacked traces in Fig. 2) peaking only at thx sirst satelmite, indibatzs chat mogovapxnt and/or trivalemt copper sites may contribute vo the chasgz redistribution between the vhxins and plangs. In order to distinguish between contributions from different cpnfigurations and to leavn
strong temperature dependence of the spectral weight main but the striking observation is polarization there are opposing trends in the satellite” and the “planes satellite” upon This suggests the intriguing possibility that there is a temperature driven redistribution of between the planes and the chains of YBCO. The spectral difference in percentages in figure derived the hatched areas relative to the total area (taking into account the atomic step between L and L 2 ) under the room temperature The difference highlights the behavior of the satellites in MST. Cu ions YBa Cu O 6.9 have charge state of +2.3. For an intermediate mixed valence system, such as YBCO, one can expect that ground-state wave of YBCO fluctuate4 different configurations and give the transitions listed in Table I, an additional (a missing) electron in the oxygen band and configurations are the effect of MLCT Supplementary Materials). Table 1 Cu transitions in different Full size table At the top of the right panel of Fig. 2, we show L 3 -spectra created using linear combinations the spectra the of the panel. Since a full theoretical description of the Cu L-XAS spectrum YBCO has proven to be too complex for state-of-the-art ab we an ionic model to project the charge-transfer from configurations. Our calculations show MLCT 3d9→2p53d9L+1 divalent sites heavily contribute to the weight of the two satellites by the double-peaked blue the opposing temperature trends in the satellites suggest existence of additional contributions besides those from copper sites. Thus the theoretical spectrum belonging to 3d9L+1→2p53d10L+1 and 3d9L−1→2p53d10L−1 (dashed traces in peaking only at the first satellite, indicates that and/or trivalent copper sites contribute to the charge redistribution between the chains and In to distinguish contributions from different and to learn
 strong temperature dependenCe of the speCtral WeiGht ArOund The mAin peak but the mOSt stRiking observation is thaT, regaRdLEss oF ThE x-ray PolarizATiON DirEcTiOn, tHeRE aRe oppOsiNg intenSity trends In tHe “Chains satellITe” And the “planEs sAtellite” upon CooLing. ThIs SugGEsts tHe iNtrigUing poSSibiliTy that theRe IS a tempERature dRIVeN redIstribution of charGE bETween the planes And the ChAInS OF YBcO. THe spectral DiFfereNCe in perCEnTAGEs dISplayed in the fIgure are derIVed From thE hAtcHEd areaS relaTiVE to The total areA (takIng into acCount tHE atomic STep betwEen L 3 anD L 2 ) uNdeR the ROoM tEmpErATurE SpEctRA. ThE differeNcE hIghliGhts THE OPposIng BehaVior oF the satelliteS in The Mst. FoRmallY, Cu ioNs in yBA 2 Cu 3 O 6.9 hAve a chArge sTaTe of +2.3. For an intermEdiaTe mixed vaLenCe SysTeM, such AS YBCO, oNe cAn eXpect thAt the grOUnd-StATE WaVe function configurAtIONs Of YBCO caN fluctUAtE4 bETween difFeRenT Cu-sITE confIgurATiOns and giVe rise TO tHe TransitIoNs listEd In TAblE I, wheRE L+1(L−1) dEnotes An additiOnal (a MIssing) electron IN the oxygen ligANd BANd ANd suCh cOnfiguratioNs arE The eFfecT Of mLCt (See SuPplemEnTArY materials).

Table 1 Cu traNsItions In difFerent configuRations FulL SIZe table

AT the TOp OF the right panel Of Fig. 2, We show simuLAted Cu L 3 -sPectrA created By using liNEAr combinAtiOns Of tHe pURE-cOnfiguration sPECtra At The bottOm oF the rigHt pAneL. SiNce A fUll theoreTical desCrIpTiOn Of tHe Cu L-xaS spectrUm Of YbCo haS provEN to be tOo comPlex FoR sTAte-Of-the-arT Ab INItio MeThOds wE emPlOy an iOnic MOdeL approaCh to projeCt tHE chaRgE-tRansfer Contributions FrOm essentiaL cOnfIguratIONs. Our calCulations show that the MLCt TransitIonS 3d9→2p53d9L+1 DeriVing from fOrmAlly diValENt coppEr siteS must HeAviLY ContrIBUtE to ThE spectral wEIGht Of the TwO satEllites (Reproduced by the douBLe-pEaked blue tracEs iN Fig. 2). hOWeVer, THe OPpoSiNG teMPErature trends in The satelliTeS SuGgest the exISteNcE of addiTional cOntriBUtions bEsides thoSe from divAlEnt cOPPer Sites. Thus tHe theoreTical specTRum beLOnGing tO 3d9L+1→2P53d10L+1 and 3D9L−1→2P53d10L−1 (DasheD blackED trAces iN Fig. 2) peAkIng onlY at thE fIrst sateLlite, indicates that monovAlent aNd/or tRivAlent coppEr sITes May contriBute To the chargE reDisTribuTioN BetweEn thE ChAinS And plAnes. iN order to dIStIngUISh Between contRIBUtiOns frOm dIFferenT conFigurations and to lEArn
 strong temperature depend ence of th e spe ctr alwe ight  aro und the main p e ak b ut the most striking o bserv at i on i s  t hat,regardl e ss o f t he  x -ra yp ol ariza tio n direc tion, ther e a re  opposing in t en sity trend s i n the “chain s s atelli te ” a n d the  “p lanes  satel l ite” u pon cooli ng .  Thiss uggests t he  int riguing possibili t yt hat there is a  tempe ra t ur e dri ven  redistrib ut ion o f  charge be t w e ent he planes and  the chains ofYBCO.Th e s p ectral  diff er e nce  in percent ages  displaye d in t h e figur e  are de rivedfro m t he h a tc he d a re a s r e la tiv e  to  the tot al  a rea ( taki n g i ntoacc ount  theatomic step b etw eenL  3and L  2 )unde rthe r oom te mpera tu re spectra. The  dif ference h igh li ght sthe o p posing  be hav ior ofthe sat e lli te s i nthe MST. Formally,  C u io ns in YB a 2 Cu 3O6 .9 haveacha rges t ate o f +2 . 3.  For aninterm e di at e mixed  v alence  s yst em,  such as Y BCO, o ne can e xpect that the groun d -state wave f u nc t i on conf igu rations ofYBCO canfluc t ua te4 betwe en di ff e re n t Cu-site configura ti ons an d giv e rise to the  transitio n s listed i n Ta b le I, where L+1(L −1) d enotes ana dditiona l (amissing)  electron i n the ox yge n l iga ndb a nd  and such con f i gura ti ons are  th e effec t o f M LCT  (s ee  Suppleme ntary Ma te ri al s) .
Table 1 Cu tra ns iti on s i n dif f erentconfi gura ti on s  Fu ll size ta b l e

A tth e to p o fthe r ight pan el of F ig. 2, we  sh o w si mu la ted CuL 3 -spectracr eated by u si nglinear c ombinati ons of the pure-configu r ation s pec tra a t th e bottomofthe ri ght panel.  Since  a fu ll  th e o retic a l  d esc ri ption of t h e  Cu  L-XA Sspec trum of  YBCO has proven t o  be  too complexfor  sta t e -o f-t h e- a rtab ini t i o methods we em ploy an io ni c  m odel appro a chto  projec t the c harge - transfe r contrib utions fr om  ess e n tia l configur ations.Our calcu l ation s  s how t hat  the M LC T t ransi tions3 d9→ 2p53d 9L+1 d er ivingfromfo rmally d ivalent copper sites mu st hea vilycon tribute t o t h e s pectral w eigh t of the t wosat ellit es( repro duce d  b y t h e dou ble- p eaked blu e  t rac e s  i n Fig. 2).H o w eve r, th e o p posing  tem perature trends i n  the satellite s su g g est  th e  exi st ence of additi ona lc o ntributi on s besides t hose fro md ivale nt cop per si tes. Th u s  t h e theo reti cal  spectrum  be lo n ging to  3 d9 L +1→2p5 3d10 L+ 1 and3d9L−1 → 2p53 d 1 0L−1 (dashed bla ckedt r acesi n F ig. 2 )peaking only  at the fi rst satelli te, in dica tes t hat mon ov alentand /o r trivalen t  copper s itesmay con tr ibut e t o thechar g e  redi stri bu tio n between t he ch ai n s a nd p lanes .In o rder to d i stinguis h b e tween c on tri b u tionsf ro m differentcon figur a t ions and t o  lea r n
 strong_temperature dependence_of the spectral weight_around the_main_peak but_the_most striking observation_is that, regardless_of the x-ray polarization_direction, there are_opposing_intensity trends in the “chains satellite” and the “planes satellite” upon cooling. This suggests_the_intriguing possibility_that_there_is a temperature driven redistribution_of charge between the planes_and the_chains of YBCO. The spectral difference in percentages_displayed_in the figure_are derived from the hatched areas relative to the_total area (taking into account the_atomic step between_L_3_and L 2 )_under the room temperature spectra. The_difference highlights the opposing behavior of_the satellites in the MST. Formally, Cu_ions in YBa 2 Cu 3_O 6.9 have a charge_state of_+2.3. For an intermediate mixed_valence system, such_as YBCO,_one can expect_that the ground-state wave function configurations_of YBCO can_fluctuate4 between different Cu-site configurations and_give_rise to the_transitions_listed_in Table_I, where L+1(L−1)_denotes_an additional_(a_missing) electron in the oxygen ligand_band_and such configurations are the effect of_MLCT (see Supplementary Materials).

Table_1_Cu transitions in different_configurations Full size table

At the_top of the right panel of_Fig. 2,_we show_simulated Cu L 3 -spectra created by using linear combinations of_the pure-configuration spectra at the bottom_of the right panel._Since a_full_theoretical description of_the_Cu L-XAS_spectrum of YBCO has proven to be_too complex_for state-of-the-art ab initio methods we_employ an ionic model_approach_to project the charge-transfer contributions from_essential configurations. Our calculations show that_the MLCT transitions 3d9→2p53d9L+1 deriving_from_formally_divalent copper sites must heavily_contribute to the spectral weight of_the two satellites_(reproduced by the double-peaked blue traces in_Fig._2). However, the opposing temperature trends_in_the satellites suggest the existence of_additional_contributions_besides those from divalent copper_sites. Thus the theoretical spectrum belonging_to 3d9L+1→2p53d10L+1 and 3d9L−1→2p53d10L−1 (dashed blacked traces in Fig._2) peaking only_at the first satellite, indicates_that_monovalent_and/or trivalent copper sites may contribute to the charge redistribution_between the_chains and planes._In order to distinguish between contributions from different configurations and_to learn