Dependence of carrier doping on the impurity potential in transition-metal-substituted FeAs-based superconductors

1.3 MB·English

by  S. Ideta

Dependence of carrier doping on the impurity potential in
transition-metal-substituted FeAs-based superconductors
S. Ideta1, T. Yoshida1,2, I. Nishi1, A. Fujimori1,2, Y. Kotani3, K. Ono3, Y.
Nakashima4, S. Yamaichi4, T. Sasagawa4, M. Nakajima1,2,5, K. Kihou2,5, Y.
Tomioka2,5, C. H. Lee2,5, A. Iyo2,5, H. Eisaki2,5, T. Ito2,5, S. Uchida1,2 and R. Arita2,6
1 Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
2 JST, Transformative Research-Project on Iron Pnictides (TRIP), Chiyoda, Tokyo 102-0075, Japan
3 3 KEK, Photon Factory, Tsukuba, Ibaraki 305-0801, Japan
1 4 Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
0 5 National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan
2 6 Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656
(Dated: January 16, 2013)
n
a In order to examine to what extent the rigid-band-like electron doping scenario is applicable
J
to the transition metal-substituted Fe-based superconductors, we have performed angle-resolved

5 photoemission spectroscopy studies of Ba(Fe1−xNix)2As2 (Ni-122) and Ba(Fe1−xCux)2As2 (Cu-
1 122), and compared the results with Ba(Fe1−xCox)2As2 (Co-122). We find that Ni 3d-derived
features are formed below the Fe 3d band and that Cu 3d-derived ones further below it. The
] electron and holeFermisurface (FS) volumesarefound toincrease anddecrease with substitution,
n
respectively, qualitatively consistent with the rigid-band model. However, the total extra electron
o
number estimated from the FS volumes (the total electron FS volume minus the total hole FS
c
- volume) is found to decrease in going from Co-, Ni-, to Cu-122 for a fixed nominal extra electron
r number, that is, the number of electrons that participate in the formation of FS decreases with
p
u increasing impurity potential. We find that the N´eel temperature TN and the critical temperature
s TcmaximumaredeterminedbytheFSvolumesratherthanthenominalextraelectronconcentration
. northe substituted atom concentration.
t
a
m PACSnumbers: 74.25.Jb,71.18.+y,74.70.-b,79.60.-i
-
d
Carrier doping plays an essential role in a variety of
n
o correlated electron systems such as the high-Tc cuprates (a) T (b)
c as well as the newly discovered ion-based high-T su- 120 N Co-122
[ c K) Ni-122
9v4 aippnneogrucano(ndSntsCidfeuA)rcFrtboeoym2rAsa.ssgu2nbFes(ottAiirctu=emtxioeaBntmaa,lpolSbferu,)mtoaobnbneebocvrooeamfvleietanhstteesdumppaaeerstreac“nlo1tna2dtc2ouo”mcmtiss-- mperature ( 8400 Tc CCCNuoui-1---11122222222
8 e
8 for divalent Ba or Sr at the A site, which obviously T 0
1 dopes the Fe-As layer with holes [1, 2]. Superconductiv- 0 0.05 0.10 0.15 0 0.05 0.10 0.15
. ity is also realized via partial substitution of transition- x, concentration of T Extra electrons per Fe/T site
5
metal atoms such as Co, Ni, and Cu for Fe [3–6].
0
2 According to the rigid-band model, the substitution
FIG.1. (Coloronline)Superconductingandmagnetictransi-
1 leads to electron doping and the doped electron num-
v: ber in Ba(Fe1−xCox)2As2 (Co-122), Ba(Fe1−xNix)2As2 Ttio=n tCeom,pNeir,aCtuur)esre(pTocrtaenddinTNR)efo.f[B4,a5(F].e1(−a)x:TPx)lo2tAtse2d,a(sTf-u1n22c-:
i (Ni-122), and Ba(Fe1−xCux)2As2 (Cu-122) is expected tionsofthenumberofsubstitutedtransition-metalatomsper
X to be x, 2x, and 3x, respectively, while it is x for Co- Fesite,x. (b): Plottedasfunctionsofnominalextraelectron
r 122. This is a remarkable phenomenon given the fact number per Fe site x, 2x, and 3x for Co-, Ni-, and Cu-122,
a
thatthe substitution oftransition-metalatomsforCuin respectively.
the CuO2 plane of the cuprate superconductors quickly
kills the superconductivity [7].
reachedatx ∼ 0.05,but the Tc dropsmorerapidly with
The phase diagrams of the transition metal-doped Ni substitution than Co substitution. Cu-122 is largely
BaFe2As2 are reported by Canfield et al. [4] and Ni non-SC except for x ∼ 0.044, where very a low Tc of
et al. [5]; however, exhibit complex behaviors as shown ∼ 2 K has been reported [4, 5]. The nearly coinciding
in Fig. 1, where the SC transition temperatures T s and T domes of Co- and Ni-122 in panel(b) (plotted against
c c
the N´eel temperatures TNs of Co-, Ni-, and Cu-122 are the nominal extra electron number) suggest that Fermi
plotted as functions of substituted atom concentration surfaces (FSs) follow the rigid-band model, but that the
x [panel (a)] and nominal extra electron concentration smallbutdistinctmismatchofthetwoTc domessuggests
[panel(b)]. TheTc ofCo-122reachesthemaximum24K that there are some changes in the electronic structure
atx∼0.06. AsforNi-122,themaximumTc of∼18Kis beyond the rigid-band model, that is, the impurity po-
2
(a) (b) 10 (a1) G Ni-122 10 (b1) G X
X
NBai-n1d2 2c a(hlcnla =ti o7n8 eV) CBaun-1d2 c2a (lhclna t=io 6n7 eV) /c)p 9 Z X 2/c)p 9 Z X
nits) k (2z 8 G x = 0.02 X k (z 8 CuG-122 (x =X 0.04)
b. u Ni 3d Cu 3d -0.5 0 0.5 1.0 1.5 2.0
Intensity (ar xxxx ==== 0000....0000385275 xxxx ==== 0000....10004974 Fe d k (2/c)pz 1098 (a2) GGZx =N i0-1.023275 XX X (2/c)kpz 1098 (b2) XXX
Cu-122 (x = 0.07)
Ni 3d Fe d Cu 3d
-8 -6 -4 -2 0 -8 -6 -4 -2 0 10 (a3) G Ni-122 X 10 (b3) X
E - EF (eV) E - EF (eV) k (2/c)pz 98 GZ x = 0.05 XX (2/c)kpz 98 XX
FIG. 2. (Color online) Angle-integrated photoemission spec- Cu-122 (x = 0.09)
traof Ni-122 [panel (a)]and Cu-122 [panel (b)]. Partial den-
sity of states for Ni and Cu 3d orbitals obtained by band- 10 (a4) G Ni-122 10 (b4) X
X
stthreuecntuerregycarlecguiloantidonom[1i9n]ataerdeablysoNpilaonttdedC.uS3hda-ddeedriavreedassthaotewss. 2/c)p 9 H Z X 2/c)p 9 X
k (z 8 G X (kz 8 X
L x = 0.08 Cu-122 (x = 0.14)
-0.5 0 0.5 1.0 1.5 -0.4 0 0.4
tentialofthesubstitutedatomsarelikelytoinfluencethe k (p/a) k (p/a)
// //
electronic structure and hence T . For Cu-122, the T is
c c
strongly suppressed, and the Tc “maximum”occurs at a
much higher nominal extra electron concentration of ∼ FIG.3. (Coloronline)ARPESintensityplotink||-kzmomen-
tum space for Ni-122 and Cu-122 obtained by hν-dependent
0.13 than Co- (∼ 0.06) and Ni-122 (∼ 0.10), suggesting
ARPES measurements. (a1)-(a4): Hole and electron FSs for
thatitselectronicstructureisstronglydeviatedfromthat Ni-122. (b1)-(b4): Hole and electron FSs for Cu-122. kF
expectedfromtherigid-bandmodel. ContrarytoT ,the pointsoftheholeandelectron FSsareplottedbyblackdots.
c
drop of the TN with doping is determined by the substi- The ARPES intensity plots have been symmetrized with re-
tuted atom concentration x rather than the number of spect tosymmetry lines.
extra electrons, as seen from the relatively well overlap-
ping TN curves in Fig. 1(a) (although the TN curve for
Co-122 is somewhat deviated from the other curves). 122 estimated from the FS volumes is smaller than the
So far, a large number of angle-resolved photoemis- value expected from the simple rigid-band model, and
sion spectroscopy (ARPES) studies have been made on decreases in going from Co-, Ni-, to Cu-122 for a fixed
the Co-122. The results have shown that there are two nominal doped electron number.
hole FSs and two electron FSs at the two-dimensional High-qualitysingle crystalsof Ba(Fe1−xNix)2As2 with
Brillouin zone (BZ) center and corner, respectively [8– x = 0.02, 0.0375 (T ∼ 16 K), 0.05 (T ∼ 18 K), and
c c
12]. The SC gaps [15, 16] and the three dimensional- 0.08 (Tc ∼ 5 - 10 K), and Ba(Fe1−xCux)2As2 with x
ity [11, 12, 18] of the hole and electron FSs have also = 0.04, 0.07, 0.09, and 0.14 were grown by the self-flux
been identified. The FSs evolve following the rigid-band method. The NiandCuconcentrationsweredetermined
model with electron doping, that is, the volumes of the by X-ray fluorescence analysis and energy dispersive X-
FSs changeaccordingto the number ofextra electrons x ray analysis, respectively. ARPES measurements were
andthe chemicalpotentialisshiftedaccordingly[12–14]. carriedout at beamline 28A of Photon Factory (PF) us-
However, according to a recent density functional the- ing circularly-polarized light ranging from hν = 34 to
ory (DFT) calculation on supercells [19], the extra elec- 88 eV and a Scienta SES-2002 analyzer with the total
tronic charges are largely distributed on the substituted energy resolution of ∼ 15 - 25 meV. The crystals were
Co, Ni, or Cu atoms, apparently contradicting with the cleavedinsituatT =10Kinanultra-highvacuumless
rigid-band model [12, 17]. On the other hand, another than1×10−10 Torr. ARPESmeasurementsonNi-122(x
supercellcalculationhasindicatedthatthetotalelectron = 0.02, TN ∼ 90 K) and Cu-122 (x = 0.04, TN ∼ 50 K)
numberenclosedbytheFSschangesinproportiontothe were performed at temperatures above TN, T = 110 K
dopantconcentrationinCo andNi-dopedLaFeAsO[20]. and60K,respectively. Theothersamplesweremeasured
In this Letter, we have performed an ARPES experi- at T = 10 K.
ment on Ni- and Cu-122, and investigated the evolution Figure2showsangle-integratedphotoemissionspectra
of the electronic structure with the strength of impu- of Ni-122 and Cu-122 in the entire valence-band region.
rity potential in going from Co-, Ni-, to Cu-122. We Ni 3d-derived emission is located ∼ 2 - 4 eV below the
find that the number of doped electrons in Ni- and Cu- Fermilevel(EF),andoverlapswiththeFe 3d band. The
3
(a) T T (b)
140 N c 25
Co-122 Co-122
120 Ni-122 (Brouet et al.,
Cu-122 Malaeb et al.) 20
K) 100 Ni-122
perature ( 8600 CCCNuoui-1---11122222222 T (K)c1150
m 40 [Canfiled et al.,
Te Ni, et al., Liu et al.] 5
20
0 0
0 0.05 0.10 0.15 0 0.05 0.10 0.15
n - n n - n
el h el h
FIG. 5. Tc and TN of Ba(Fe1−xTx)2As2 (T = Co, Ni, Cu)
plottedasfunctionsofthetotalFSvolumenel -nh evaluated
by ARPES. The data for Co-122 are taken from [4, 5]. (b)
is a magnified plot of Tc. The Tc values for Co-, Ni-, and
Cu-122aretakenfrom [4,5,11,12,25]. Thenel−nh ofCo-,
Ni-, and Cu-122 for small x’s has been estimated by linear
interpolation between the lowest nel−nh data and nel−nh
= 0. TN for Ni-122 with x = 0.02 and Cu-122 with x = 0.04
are also plotted.
hole FSs were observed only for x = 0.04 as shown in
FIG.4. (Coloronline)HoleandelectronFSvolumesfromthe
Fig. 3(b1), and we show only the electron FSs for x =
ARPES dataof BaFe2As2, Co-122, Ni-122, and Cu-122 plot-
ted as functions of the nominal extra electron number. (a): 0.07,0.09,and0.14inFigs. 3(b2)-3(b4)(seeFigs. 6and
Hole FS volume nh. (b): Electron FS volume nel. (c): Total 7 and the text of [23]).
FS volume nel −nh. Black dashed line shows the behavior Now, we estimate the total hole and electron FS vol-
(nel−nh = extra electron per Fe/T site) expected from the umes in order to discuss to what extent the electron-
rigid-bandmodel. BaFe2As2 andCo-122dataaretakenfrom
doped system can be understood within the rigid-band
[11, 12].
model. First,letusestimatethevolumeofeachholeand
electron FS from the result of the FS mapping shown in
Fig. 3. For the “rugby ball” like hole FSs of Ni-122,
Cu 3d-derived emission is located at higher binding en-
we have estimated the volumes assuming two degener-
ergies of ∼ 4 - 5 eV. This indicates that the impurity
ate inner (x = 0.02, 0.0375, and 0.05) and one outer (x
potential of the substituted transition metal atoms be-
= 0.02, 0.0375, 0.05, and 0.08) hole FSs [12] (see also
comes stronger in going from Co, Ni, to Cu. The spec-
Supplemental Material in Fig. 8). For the hole FS of
tra are consistent with the density of state given by the
Cu-122with x = 0.04,we applied the same method. For
super-cell band-structure calculation [19] shown in the
the electronFSs, we havealsoestimatedthe volumesas-
same figure.
sumingthattwoFSsarenearlydegenerateasinthecase
Figure 3 shows the summary of FS mapping in kk-kz of Co-122 [24]. The total volume of the hole FSs, nh,
space for the hole and electron FSs of Ni- and Cu-122. that of the electron FSs, nel, and the total FS volume,
Raw data of hole and electron bands near EF are shown namely, the difference nel −nh are plotted as functions
in Fig. 7 of Supplemental Material. While the two hole of nominal extra electron number in Fig. 4. In order
FSs around the Z point are always observed, the hole to compare the present ARPES result with the previous
FS around the Γ point shrinks and disappears with in- studiesofCo-122[11,12], nh andnel areplottedasfunc-
creasingNi concentration,resultingin three-dimensional tions of the nominal electron number, x for Co, 2x for
hole FSs [21, 22]. On the other hand, the volumes of Ni, and 3x for Cu in Figs. 4(a) and 4(b). (Data for Co-
the electron FSs around the X point become larger with 122 with x < 0.05 are not plotted here because of the
increasing Ni concentration, indicating electron doping. antiferromagnetic band folding and hence the difficulty
All the FSs show warping along the kz directionand the inestimating nh andnel.) Inthe previousARPESresult
electron FS is less warpedthan the hole FS. For Ni- and on Co-122 [11, 12], the plots of nh from the non-doped
Cu-122,wecouldnotresolvethetwoelectronbands,and to overdoped samples decreases gradually with increas-
therefore, we consider that the two bands are almost de- ing Co concentration as shown in Fig. 4(a). The nh of
generate. As a whole, the hole andelectronFSs are sim- Ni-122 exhibits the same behavior. In Fig. 4(c), one
ilar to those of Co-122 [11]. In the case of Cu-122, the finds that nel −nh for Co-122 [12] is proportional to x
4
for x ≥ 0.07, where the anti-ferromagnetic order disap- electron occupation. This calculated result can be com-
pears. Ontheotherhand,thevalueofnel−nh forNi-122 paredwith the FS volume changesin the series T = Co,
increases, but seems to be slightly deviated downwards Ni, and Cu for the same number of extra electrons esti-
from the linear relationship predicted by the rigid-band mated in the present ARPES study. In going from Ni to
model,indicatingthatsignatureofthedeviationfromthe Cu, the impurity potential becomes stronger as demon-
rigid-band model starts to be seen from Ni-122. As for stratedinFig. 2andthehole-FSvolumedecreases. How-
Cu-122,nel−nhisevensmallerthanthatofNi-122inthe ever, since the total electron number estimated from the
entiredopingrange. ThepresentARPESresultsuggests FSvolumesshowasmallervaluethanthatexpectedfrom
that although most of the doped electrons participate in the rigid-band model, both the calculation and experi-
the formation of FSs, part of them may be partially lo- mental results show decrease in the electron occupation.
calized and do not fill the energy bands as predicted by For Co-122, the electronic structure almost follows the
the rigid-band model. Recent Neutron scattering study rigid-bandmodel, because the Co 3d level is near the Fe
hasalsoreportedthattheelectroncountingbasedonthe 3d level.
rigid-band model is inappropriate [26]. By computing the configuration-averaged spectral
The plots of nh for Co-, Ni-, and Cu-122 shown in function of disordered Co/Zn substituted BaFe2As2,
Fig. 4(a) almost coincide with each other. On the other Berlijn et al. [29] have estimated the hole and electron
hand, the nel curve shown in Fig. 4(b) is shifted toward volumes. For Co-122, the FS volume of Co-122 follows
higher electron concentrations in going from Co, Ni, to the Luttinger theorem, that is, the system follows the
Cu. This means that in going from Co-, Ni-, to Cu-122, rigid-band model. On the other hand, for Zn-122, the
the hole bands are shifted away from EF by the same Luttinger theorem breaks down. The result also indi-
ratio, and that the relative positions of the electron and cates that the FS volume is smaller than that expected
hole bands change (see Supplemental Material, Figs. S4 from the rigid-band model. Therefore, the increased de-
and S5 of [23]), indicating that the non-rigid band effect viation from the rigid-band model becomes stronger in
clearly exists. going from Co, Ni, to Cu-122 is consistent with the cal-
So far, we haveshownthat electronsareindeed doped culatedresultfor Zn-122. Thus,to understandthe effect
in the transition metal-substituted BaFe2As2, but the of the transition-metal atom substitution for Fe atoms
deviation from the rigid-band model exists in the band on the electronic structure, the strength of the impurity
structureandtheFSvolumesandincreaseswithincreas- potentialshouldbe takeninto account. The calculations
ing strength of the impurity potential. As shown in Fig. have also shown that all the spectral features of Zn-122
1(b), the extra doped electron concentration determines are broadened compared to Co-122. In fact, the hole
the Tc better than the impurity concentration, but the and electron bands for Ni- and Cu-122 are not clearly
T for Co-, Ni-, and Cu-122are still significantly de- resolved into multiple bands, whereas those of Co-122
c,max
viated from each other in this plot. As for TN, the same and BaFe2As2 have been clearly resolved. In the stud-
plot fails, particularly in Cu-122. On the other hand, ies of conventional binary random alloys, photoemission
if the Tc and TN for Co-, Ni-, and Cu-122 are plotted spectroscopyandtheoreticalcalculationbythecoherence
as functions of nel−nh deduced from the ARPES data potential approximation(CPA) [32–37] have shown that
[27], in Fig. 5 the TN for Co-, Ni-, and Cu-122 coincides the rigid-band model breaks down when the potential
with each other, and the T maximum occurs at nearly difference between two constituent atoms is comparable
c
the same nel −nh value of ∼ 0.06 for all the systems. to or exceeds the band widths. In the latter case of al-
This means that the TN values as well as the optimal loys, characteristic features in the densities of states of
composition of Tc in the electron-doped BaFe2As2 are the two constituent materials survive. In this sense, the
controlled by nel −nh relatively well. Since the Tc,max present ARPES result may be understood in analogy of
variesbetweenthesystems,theabsoluteT valuesshould the conventionalbinary alloys.
c
be controlled not only by nel−nh, but also by other pa- In conclusion, we have performed an ARPES study
rameter(s) such as nh, nel, or the band structure. Since of the transition metal-substituted Ba(Fe1−xTx)2As2 (T
the energy position of the impurity 3d level is loweredin = Ni, Cu) to investigate the validity of and the devia-
going from Co, Ni, to Cu, it is natural to consider that tion from the rigid-band model, which has been usually
the strong impurity potential suppresses the Tc value. assumed for Co-122. We find that, although the rigid-
Recently, Haverkort et al. [28] and Berlijn et al. [29] band model works qualitatively and electrons are indeed
have studied how the electronic structure is affected by doped, the electron FS volumes in Ni- and Cu-122 are
impurity potential when host atoms are substituted by smaller than the value which is expected from the rigid-
other atoms. It has been shown that the hole-FS vol- band model. This result suggests that part of electrons
ume increases with increasing impurity potential [20]. doped by substitution of Ni or Cu preferentially occupy
For strong impurity potentials, substitution creates an the Ni 3d or Cu 3d states, or are trapped around the
impurity band split-off below the original host band impurity sites, and do not behave like a mobile carrier.
[19, 30, 31]. The impurity band removes electrons from We foundthat the TN inthe electron-dopedBaFe2As2 is
the host band, leading to an apparent decrease in the determined by nel−nh, while Tc is determined by both
5
nel−nh,thebandstructure,andchemicaldisorder,which 7(a1)-(a3) and Figs. 7(b1)-(b3) and (c1)-(c4), respec-
are affected by the impurity potential. tively. We refer to the inner and outer hole bands as α
Enlightening discussions with H. Wadati, G. A. andβ,respectively,whilewerefertotheelectronbandas
Sawatzky, R. M. Fernandes, and M. Ogata are grate- δ. Concerning the electron bands around the X point of
fully acknowledged. ARPES experiments were carried Ni-122 and Cu-122, one cannot resolve the two electron
out at KEK-PF (Proposal No. 2009S2-005). This work bands. The hole bands denoted by α+β of Cu-122 with
was supported by an A3 Foresight Program from Japan x = 0.07 does not cross EF around the Z and Γ points
Society for the Promotionof Science, a Grant-in-Aid for as shown in Figs. 7(c1)-(c4).
Scientific Research on Innovative Area “Materials De- In order to show how we have deduced the number of
signthroughComputics: Complex CorrelationandNon- hole bands in Ni-122, we show the second-derivative of
Equilibrium Dynamics”, and a Global COE Program the EDCs in E −k space. As shown in Fig. 8, in the
“Physical Sciences Frontier”, MEXT, Japan. S.I. ac- slightlyundedoped (x =0.0375)andoptimally doped(x
knowledges support from the Japan Society for the Pro- = 0.05) samples, two hole bands cross the EF, while in
motion of Science for Young Scientists. the overdoped(x = 0.08)sample, one of them is slightly
belowthe EF. Forthe estimationofthe holeFS volume,
we assume one outer hole FS for x = 0.02, 0.0375, 0.05,
SUPPLEMENTAL MATERIAL and 0.08 samples and two degenerate inner hole FSs for
x = 0.02, 0.0375, and x = 0.05 samples [12].
1. Fermi surface mapping for Ni-122 and Cu-122
Figure 6(a) shows ARPES intensity plots of
3. Shifts of hole- and electron-energy bands
Ba(Fe1−xNix)2As2 (Ni-122) in@two-dimensional mo-
mentum space for the underdoped (x = 0.02), slightly
underdoped (x = 0.0375), optimally doped (x = 0.05), AsshowninFigs. 9(a1)and9(a2),theholebandmax-
and overdoped (x = 0.08) samples. As for the hole imaofNi-122andCu-122aroundthe Γ pointareshifted
FSs, the k -k cross-sectional area of one of the hole by∼30meVand∼40meV,respectively,comparedwith
x y
Fermi surfaces (FSs) around the Z point (kz ∼ 2π/c) that of the band dispersions of BaFe2As2 [11]. On the
decreases with increasing x as shown in the upper panel other hand, the shifts of the minimum energies of the
of Fig. 6(a), and that around the Γ point (k ∼ 0) electron bands of Ni-122 and Cu-122 are ∼ 35 meV and
z
disappears as shown in the lower panel of Fig. 6(a) in ∼ 25 meV, respectively, comparedwith that of the band
the optimally-doped and slightly underdoped Ni-122. dispersionsofBaFe2As2 [11]asshowninFigs. 9(a3)and
This indicates that the hole FS of Ni-122 has strong 9(a4). The energy shifts of the hole and electron bands
threedimensionalityasinthecaseoftheparent[11]. On for Ni-122 are almost the same, while those for Cu-122
the other hand, the area of the electron FSs around the show a remarkable difference, indicating that the devia-
X point as shown in Fig. 6(a) gradually expands with tion from the rigid-band model becomes strong in going
electron doping. In Fig. 6(b), ARPES intensity plot from Ni- to Cu-122.
of Ba(Fe1−xCux)2As2 (Cu-122) is shown for x = 0.04, In Figs. S5(a) and S5(b), we have plotted the doping
0.07, 0.09, and 0.14. The hole FS has been observed at dependences of the energies of the hole-band maximum
Cu-122 with x =0.04 at the Z and Γ points, while the and the electron-band minimum of Fig. 9 together with
hole FSs are not clearly observed even though there are the ARPES results on Co-122 [12, 13, 25]. For the hole
finite intensities at and around the Γ and Z points for x band, Co- and Ni-122 show the almost rigid-band shift.
= 0.07, 0.09, and 0.14 (see Fig. 7). On the other hand, On the other hand, the hole band of Cu-122 is strongly
one can see a large electron FS around the X point for deviated from the rigid-band model. The energy shifts
all the samples. The band-structure calculation of the oftheelectronbandforNi-andCu-122showadeviation
parent compound BaFe2As2 [21] suggests that the hole from the rigid-band model and those of Co-122. These
FS should exist at the Z point if the rigid-band model is non-rigid-band shifts are consistent with the results of
applicable. However, the hole band of Cu-122 does not the nh and nel curves shown in Figs. 4(a) and 4(b) in
cross the Fermi level (EF) even around the Z point as the main text.
shown in Fig. 7, indicating that the hole FSs disappear
for x = 0.07, 0.09 and 0.14.
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7
FIG. 6. ARPES intensity plot of Ba(Fe1−xNix)2As2 (Ni-122) and Ba(Fe1−xCux)2As2 (Cu-122). Intensity has been integrated
over the energy range ± 5 meV of EF. Solid green and dashed black circles on the Fermi surfaces (FSs) show experimentally
determined Fermi momentum (kF) and schematic FSs, respectively. (a): Ni-122 with x = 0.02, 0.0375, 0.05, and 0.08 referred
to Ni0.02, Ni0.0375, Ni0.05, and Ni0.08, respectively. kzs measured with photon energies of hµ= 60 and 78 eV are near the
∼ Z and ∼ Γ points, respectively. (b): Cu-122 with x = 0.04, 0.07, 0.09, and 0.14 referred to Cu0.04, Cu0.07, Cu0.09, and
Cu0.14, respectively.
8
FIG. 7. ARPES spectra of Ni-122 and Cu-122. (a1)-(a3): Energy-momentum (E−k) plot around the Z, Γ and X points for
Ni0.02. (a4)-(a6): Second-derivativeE−k plots of (a1)-(a3). (b1)-(b3): E−k plot around the Z, Γ and X points for Cu0.04.
(b4)-(b6): Second-derivative E −k plots of (b1)-(b3). (c1),(c3): E −k plots around the Z and Γ points for Cu0.07. Even
around the Z point, the band does not cross the EF. Panels (c2) and (c4) are EDCs corresponding to panels (c1) and (c3),
respectively. Gray dashed curves are guide to theeye.
9
FIG.8. (a)-(c): Second-derivativeE−k plotsofNi-122takenathν =60eV,correspondingtokz aroundtheZpoint. Dotted
lines are guideto the eyeto trace hole bands.
(a1) (a2) (a3) (a4)
100 50
hole (G) EDC M D xC = 0.0 EDC M D Cx = 0.0 Ni-122 Cu-122
50 xxx === 000...00023575 xxx === 000...000479 0 electron (X)
x = 0.08 x = 0.14
V) 0 V)
me me -50
(EF -50 (EF
E - E - -100 EDC M D xC = 0.0 EDC M D xC = 0.0
-100 x = 0.02 x = 0.04
x = 0.0375 x = 0.07
Ni-122 Cu-122 x = 0.05 x = 0.09
-150 -150 x = 0.08 x = 0.14
-0.4 0 0.4 -0.4 0 0.4 -0.4 -0.2 0 0.2 0.4 -0.4 -0.2 0 0.2 0.4
k// (p/a) k// (p/a) k// (p/a) k// (p/a)
FIG. 9. Hole bands around the Γ point [(a1) and (a2)] and the electron bands around the X point [(a3) and (a4)] for Ni-122
and Cu-122. Band dispersions of BaFe2As2 are taken from [11].
0.02 (a) Cu (b)
Ni
0 Hole (G) Co [Neupane et al.] Electron (X)
BaFeAs [Neupane et al.]
-0.02 Rigid2-ba2nd model
V) -0.04
e
(EF -0.06 [Ma laBeabF ee2tA as2l.]
E - -0.08 Cu
Ni
Co [Brouet et al.]
-0.10
Co [Liu et al.]
Rigid-band model
-0.12
0 0.2 0.4 0 0.2 0.4
Extra electrons per Fe/T site Extra electrons per Fe/T site
FIG. 10. Shifts of the hole-band maximum around the Γ point (a) and the electron-band minimum around the X point (b).
The dashed lines show the shifts expected from the rigid-band model based on the non-magnetic band structure of BaFe2As2
[21]. Data of BaFe2As2 and Co-122 for the hole band are taken from [11, 12, 25] and that of BaFe2As2 and Co-122 for the
electron band are taken from [13].