Molecule-Confined Engineering toward Superconductivity and

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Molecule-confined engineering towards superconductivity and ferromagnetism in two-dimensional superlattice Zejun Li, Yingcheng Zhao, Kejun Mu, Huan Shan, Yuqiao Guo, Jiajing Wu, Yueqi Su, Qiran Wu, Zhe Sun, Aidi Zhao, Xuefeng Cui, Changzheng Wu, and Yi Xie J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b10071 • Publication Date (Web): 25 Oct 2017 Downloaded from http://pubs.acs.org on October 25, 2017

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Journal of the American Chemical Society

Molecule-confined engineering towards superconductivity and ferromagnetism in two-dimensional superlattice Zejun Li§†, Yingcheng Zhao§†, Kejun Mu§‡, Huan Shan†, Yuqiao Guo†, Jiajing Wu†, Yueqi Su†, Qiran Wu†, Zhe Sun‡,//, Aidi Zhao†, Xuefeng Cui†, Changzheng Wu*,† and Yi Xie† † Hefei National Laboratory for Physical Sciences at the Microscale, CAS center for Excellence in Nanoscience, and CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei, Anhui 230026, PR China. ‡ National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, PR China. // Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, PR China. * Corresponding Authors. E-mails: [email protected] KEYWORDS：Two-dimensional superlattice; Superconductivity; Ferromagnetism; Molecule; Surface chemistry ABSTRACT: Superconductivity is mutually exclusive with ferromagnetism, because ferromagnetic exchange field is often destructive to superconducting pairing correlation. Well-designed chemical and physical methods have been devoted to realize their coexistence only by structural integrity of inherent superconducting and ferromagnetic ingredients. However, such coexistence in freestanding structure with non-superconducting and non-ferromagnetic components still remains a great challenge up to now. Here, we demonstrate a molecule-confined engineering in two-dimensional organic-inorganic superlattice using a chemical building-block approach, successfully realizing first freestanding coexistence of superconductivity and ferromagnetism originated from electronic interactions of non-superconducting and non-ferromagnetic building blocks. We unravel totally different electronic behavior of molecules depended on spatial confinement: flatly-lied Co(Cp)2 molecules in strongly-confined SnSe2 interlayers weaken coordination field, leading to spin transition to form ferromagnetism; in the meanwhile electron transfer from cyclopentadienyls to Se-Sn-Se lattice induces superconducting state. This entirely new class of coexisting superconductivity and ferromagnetism generates unique correlated state of Kondo effect between the molecular ferromagnetic layers and inorganic superconducting layers. We anticipate that confined molecular chemistry provides a newly powerful tool to trigger exotic chemical and physical properties in two-dimensional matrices. INTRODUCTION

and

Ever since the discovery of superconductivity (SC) in 1911,

superconductor17.

enormous amounts of research interests have been

ferromagnetism (FM) is usually detrimental to the

attracted in physics, chemistry and material science due

singlet pairing correlation, coexistence of SC and FM in

magnetism,

e.g.

AuIn2

Unfortunately,

to their fascinating properties . Especially, the interplay

naturally formed crystal is rare18,19.

1-6

ferromagnetic because

studies of superconductivity and magnetism are the

Great efforts have therefore been devoted to artificially

central topics in solid-state materials, appealing for

coexisting

future intriguing applications such as smart response

ferromagnetism via physical and chemical approaches.

devices, quantum computing and superconducting

Such

spintronics7-16. Since conventional superconductivity is

integrating

arising from the Cooper pairs formed by electron pairing

superconducting materials20-24. For example, fabricating

interactions

SC/FM multilayer structure consisting of alternating

with

spin-singlet,

electron

exchange

coupling is critical to the interplay of superconductivity

systems

coexistence two

superconducting

ACS Paragon Plus Environment

of

can

superconductivity

be

separated

and

typically

prepared

ferromagnetic

ferromagnetic

layers

and by and

with


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well-defined lattice matching25,26; chemical self-assembly periodically interleaved with superconducting [TaS2]

-0.33

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tunable structure. Herein,

we

demonstrate

a

molecule-confined

anions and ferromagnetic [MII0.66MIII0.33(OH)2]+0.33 cations

engineering in a 2D organic-inorganic superlattice to

using their electrostatic interactions27; the iron-based

realize a completely-new coupled electronic system,

superconductor, [(Li1-xFex)OH](Fe1-yLiy)Se, comprising

representing the first freestanding coexistence of

with superconducting (Fe1-yLiy)Se and ferromagnetic

superconductivity and ferromagnetism originated from

(Li1-xFex)OH layers28, respectively. In addition, chemical

interlayered interactions of non-superconducting and

designs of hybrid materials with superconducting

non-ferromagnetic building blocks (Figure 1). We

organic molecules and magnetic inorganic metal

unravel a spatially-confined molecular effect in 2D

complexes have also presented SC with local disordered

organic-inorganic

magnetic

states29-31.

Co(Cp)2

NbSe2

interlayer space weaken their coordination field,

nanosheets had been reported by surface-structural

triggering spin transition to high-spin state with

modulation, where ferromagnetic phase was induced

ferromagnetic behaviour; cyclopentadienyls of Co(Cp)2

within the superconducting NbSe2 frameworks32. Unlike

molecules confined in 2D SnSe2 interlayers strongly

the above integrity of intrinsic superconducting and

couple with Se-Sn-Se inorganic lattice, giving rise to

ferromagnetic components, the coexistence has also

electron transfer into the SnSe2 lattice to produce

been observed in the well-known two-dimensional (2D)

superconductivity.

interface of LaAlO3 and SrTiO333-36, representing an

superconductivity and ferromagnetism leads to a

extraordinary electronic coupling system since both the

remarkable coupled interaction of Kondo effect between

individual components are neither superconducting nor

the molecular ferromagnetic layers and inorganic

ferromagnetic states.

superconducting layers. The molecular confinement by

However, in view of the prominence of these efforts, a

chemical tailoring provides an entirely new path to

fundamental question arises if such coexistence can be

engineer the SC and magnetism in 2D hybrid materials.

imprinted

into

heterostructure

a

coexistence

confined

molecules (Cp represents cyclopentadienyl37,38) in SnSe2

and

the

superlattice:

of

superconductivity

Recently,

ferromagnetism

freestanding

with

and

in

This

unusual

coexistence

of

layer-tunable

non-superconducting

and

non-ferromagnetic building blocks. The freestanding and tunable structure makes it possible for controlled magneto-electronic

properties

and

nanofabrication

devices. On the other hand, such an integrated structure represents a new strongly coupled coexisting system, providing a promising material platform to study the exchange interplay of SC and FM. Also, since appearance of superconducting and ferromagnetic states must be originated from coupled interactions between the two non-superconducting

and

non-ferromagnetic

components, we deduce that enhanced SC-FM interplay would be expected in this coexisting system. To this end,

Figure 1. Superconductivity and ferromagnetism in

we focus on the layered hybrid structure with interlayed

two-dimensional

electronic coupled effects, which is thus expected to

superlattice.

produce

superconducting

and

magnetic

ordering.

Moreover, the adjacent SC and FM layers are coupled to each other by weak van der Waals interactions, rendering it feasible to achieve a freestanding and

organic-inorganic

SnSe2-Co(Cp)2

RESULTS AND DISCUSSION Synthesis

and

characterizations:

SnSe2-Co(Cp)2

organic-inorganic hybrid superlattice was obtained by solution-based molecular intercalation approach (for


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details see EXPERIMENTAL SECTION). We then studied the structure of the as-obtained intercalated sample by X-ray diffraction (XRD) analysis. As shown in Figure 2a, pristine SnSe2 crystal exhibits diffraction peaks of (00l) planes with the interlayer distance of 6.1 Å39. Of note, in freshly intercalated sample, all these (00l) peaks shift towards lower angles and the corresponding interlayer distance increases to be about 11.7 Å, implying an expansion of the SnSe2 van der Waals gap. This increase of interlayered space indicates the intercalation of organic Co(Cp)2 molecules into SnSe2 layers. Thin SnSe2-Co(Cp)2 superlattice nanoflakes can be obtained by exfoliating the superlattice (Figure S1 and S2). Figure 2b shows the atomic force microscope (AFM) image of the SnSe2-Co(Cp)2 nanoflake, retaining 2D morphology and layered characterization. To accurately determine

Figure 2. The structure of SnSe2-Co(Cp)2 superlattice. (a) XRD patterns of the superlattice and host SnSe2

the interlayer distance, we further measured the

crystal. (b) AFM image of exfoliated nanoflake of the

cross-section of SnSe2-Co(Cp)2 nanoflake by high-angle

superlattice. (c) The lateral HAADF-STEM image of

annular dark-field

scanning

transmission

electron

microscopy (HAADF-STEM). As illustrated in Figure 2c, the white stripes represent the SnSe2 layers and the dark

the SnSe2-Co(Cp)2 superlattice nanoflake. (d) HAADF image of the basal plane of SnSe2-Co(Cp)2 superlattice. The inset shows the corresponding SAED pattern.

regions represent the Co(Cp)2 molecules. The measured interlayer space in the lateral HAADF-STEM image is

properties. XANES is able to reveal the orientation of the

determined to be 11.7 Å, which is in good agreement

Co(Cp)2 molecules in the SnSe2 interlayers based on

with the result of XRD pattern. Raman spectra suggested

angle-dependent absorption of cyclopentadienyl planes.

that SnSe2-Co(Cp)2 superlattice flake kept the structure

Thus, angle-resolved carbon K-edge XANES spectra

of pristine SnSe2 (Figure S3). And, the EDS also revealed

were collected with various angles (θ) of the superlattice

the presence of Co(Cp)2 molecules in the obtained

basal plane with respect to the incident beam. For a

superlattice

flake

demonstrate that

(Figure

S4).

All

the SnSe2 layers

these

results

π-conjugated system as cyclopentadienyl ring, 1s-π* and

and

Co(Cp)2

1s-σ* transitions occur when the electric vector of

an

incident light is parallel to the orientations of

organic-inorganic hybrid superlattice. In addition, the

corresponding π* and σ* orbitals, that is, perpendicular

basal HAADF image and corresponding selected-area

and parallel to the molecule plane, respectively40-42. As

electron diffraction (SAED) demonstrate that SnSe2 host

depicted in Figure 3a and b, the peaks at 283.6 eV and

remains hexagonal structure with good crystallinity after

286.0

formation of SnSe2-Co(Cp)2 superlattice (Figure 2d).

cyclopentadienyl, while those at 287.4 eV, 291.0 eV and

The molecular conformation and interlayered electronic

296.6 eV come from σ* resonances. We can see that the

molecules

stack

alternatingly,

producing

eV

originate

from

π*

resonances

of

interactions determine chemical and physical properties

π* resonances show maximum intensity when θ=90°

of the obtained hybrid superlattice. To probe the

and

Co(Cp)2 molecular orientation confined in the SnSe2

corresponding change of σ* resonances have the

layers of hybrid superlattice, angle-resolved X-ray

opposite trend. This linear dichroism indicates that the

absorption

was

C5 axes of Co(Cp)2 molecule is parallel to the basal plane

performed. It is known that the Co(Cp)2 molecule has

of the 2D superlattice structure (Figure 3c), which

two characteristic cyclopentadienyls with aromatic

means that the Co(Cp)2 molecules are lying on the SnSe2

near-edge

spectroscopy

(XANES)

weaken with the decrease of θ, and


the


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Figure 3. Conformation of Co(Cp)2 molecules between SnSe2 layers. (a) Angle-resolved X-ray absorption near-edge spectra (XANES) of the superlattice flake. (b) The enlarged XANES. (c) Schematic of Co(Cp)2 molecules lied in SnSe2 interlayer. (d) STM image of the pristine SnSe2 crystal. (e) STM image of the Co(Cp)2 molecules in the SnSe2-Co(Cp)2 superlattice. (f) Schematic illustrates that Co(Cp)2 molecules lie on SnSe2 layer.

layers.

tending to organize head by head to form a short-range

Short-range ordered arrangement of the intercalated

chain geometry (Figure 3f).

Co(Cp)2 molecules was directly imaged by scanning

Coexisting SC and FM: Strikingly, superconductivity

tunneling microscopy (STM). In contrast, we first

and ferromagnetism were observed in the SnSe2-Co(Cp)2

performed the atomic resolution STM image of pristine

superlattice. It is known that the SnSe2 host material is a

SnSe2 lattice as illustrated in Figure 3d, the surface is flat

non-magnetic semiconductor43,44, and pristine Co(Cp)2

and Se atoms can be clearly seen. For the STM

is a paramagnetic molecular crystal (see Figure S5).

measurement

Notably,

of

SnSe2-Co(Cp)2

superlattice,

the

SnSe2-Co(Cp)2

superlattice

shows

superlattice was cleaved in ultrahigh vacuum to expose

superconducting and ferromagnetic properties, which is

the

STM

verified by the resistivity and magnetic measurements.

The

Figure 4a shows the temperature dependence of

intercalated

measurements

Co(Cp)2

were

molecules.

performed

at

The 70

K.

corresponding STM image shown in Figure 3e reveals

resistivity for the SnSe2-Co(Cp)2 superlattice nanoflakes

that close-packed Co(Cp)2 molecules adsorbed on SnSe2

from 300 K to 2 K at zero magnetic field, which is

layer to form monolayer domains. Of note, the two-lobe

conducted by four-probe devices (see Figure S6). The

symmetrical

are

resistivity decreases with the decrease of temperature,

corresponding to its double cyclopentadienyl rings. This

exhibiting a metallic state. An abnormal peak of

indicates that all the Co(Cp)2 molecules are lying on the

resistivity occurs at about 100 K, which could be

SnSe2

rings

attributed to a charge density wave (CDW)-like

perpendicular to the basal plane, which is consistent

transition. Further cooling causes a significant drop of

with the aforementioned XANES results. Moreover, we

resistivity to zero below 5 K, indicating that the

can see that the Co(Cp)2 molecules exhibit a certain

SnSe2-Co(Cp)2 nanoflakes transform from a normal state

degree of ordered arrangement on the SnSe2 planar layer,

to a superconducting state. The low-temperature region

layers

patterns

with

in

their

the

STM

image

cyclopentadienyl


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respectively. It can be seen that the normal resistivity of SnSe2-Co(Cp)2 nanoflake exhibits no obvious variation with magnetic field at temperature of 6.0 K above Tc. While in the superconducting state at 2.0 K, the sample keeps zero resistance below 800 Oe. As the magnetic field

further

increases,

the

resistivity

increases

monotonously and the superconductivity is completely suppressed above the critical field around 3000 Oe. This magneto-transport behavior suggested that the obtained SnSe2-Co(Cp)2 superlattice nanoflake exhibited type II superconductivity. The superconducting state and ferromagnetic signature of SnSe2-Co(Cp)2 superlattice nanoflakes were affirmed by following temperature dependence of the resistivity and magnetization measurements. Figure 5a shows the temperature-dependent

resistivity

under

different

magnetic fields. It can be seen that the superconducting temperature (Tc) reduces with the applied magnetic fields and the transition becomes less sharp. Finally, the superconductivity is completely suppressed above the Figure

4.

Superconductivity

in

critical

SnSe2-Co(Cp)2

field

around

3000

Oe.

The

magnetic

superlattice nanoflakes. (a) Temperature dependent

measurements further confirm the superconductivity

resistivity of SnSe2-Co(Cp)2 superlattice nanoflake at

and accompanying ferromagnetic behavior. As shown in

zero magnetic field (b) Resistivity as a function of

Figure 5b, under a small magnetic field of 20 Oe, the temperature dependence of magnetization (M-T curve)

magnetic field in various temperatures.

was measured in an interval from 300 K to 2 K, for both is presented in detail in the inset of Figure 4a,

zero-field-cooling (ZFC) and field-cooling (FC) process.

convincingly confirming the superconducting transition.

Both curves exhibit a sharp decrease of magnetization at

In addition, we also observed a low-temperature upturn

around 5 K and the sample becomes diamagnetic

in resistivity around 8 K as shown in inset of Figure 4a.

behavior due to the Meissner effect, which is a typical

The abnormal increase in the resistivity below 8 K can

character of superconducting state. In order to further

be well ﬁtted to a logarithmic temperature-dependent

investigate

resistivity, revealing the model of Kondo effect in the

superlattice, we measured the isothermal magnetization

SnSe2-Co(Cp)2 superlattice45,46. This unique phenomena

curve (M-H curve) of the sample at 10 K and 2 K. At 10 K,

of the Kondo effect indicate the direct interaction

the M-H curve represents an “S” shape accompanied

between conducting electrons and the local magnetic

with clear magnetic hysteresis loop, a signature of

moments in the SnSe2-Co(Cp)2 superlattice. To further

underlying

probe

ferromagnetic

the

superconductivity

characteristic

of

SnSe2-Co(Cp)2 superlattice nanoflake, field-dependent

the

magnetism

of

ferromagnetic character

the

state, in

the

SnSe2-Co(Cp)2

suggesting SnSe2-Co(Cp)2

superlattice (Figure 5c). The temperature dependence of

resistivity measurements were carried out. The direction

hysteresis loops were shown in Figure S7. Furthermore,

of the applied magnetic ﬁeld was perpendicular to the

we measured M-H curve at 2 K in superconducting state

nanoflake basal plane. Figure 4b depicts the field

as illustrated in Figure 5d. The obtained curve

dependence

SnSe2-Co(Cp)2

represents a combination of superconducting and

superlattice nanoflakes at temperatures of 2.0 and 6.0 K,

ferromagnetic features. At low field region, it represents

of

the

resistivity

for



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Page 6 of 11

Figure 5. Superconductivity and ferromagnetism in the SnSe2-Co(Cp)2 nanoflakes. (a) Temperature dependence of the resistivity of the SnSe2-Co(Cp)2 superlattice nanoflake under different magnetic fields. (b) Temperature dependence of the magnetization of the SnSe2-Co(Cp)2 superlattice under a magnetic field of 20 Oe for ZFC and FC processes. (c),(d) Isothermal magnetization curves (M–H curves) at 10 K and 2 K, respectively.

typical diamagnetic character of superconductivity; and

Mechanism of emerging SC and FM: The strong

along with the increase of magnetic field, the magnetic

electronic

behavior gradually transforms to ferromagnetism. In

molecules and SnSe2 lattice trigger electron donating to

constract, the M-H curves at 4 K and 5 K were presented

SnSe2

in Figure S8, which showed the coexistence of

emergence of superconductivity. To elucidate how

superconductivity

the

superconductivity appeared in semiconducting SnSe2

superconducting features decrease with increasing the

layers, we performed angle resolved photoemission

temperature. In order to deeply understand the

spectroscopy (ARPES) measurements of the Fermi

superconductivity, London penetration length and

surface and band structure of SnSe2-Co(Cp)2 superlattice.

Cooper pair density have been calculated (see in

Figure 6a shows the ARPES spectra of the SnSe2-Co(Cp)2

supporting information). Furthermore, combining with

superlattice measured in the energy-momentum space

the

an

along the Г–M direction at 12 K. The band dispersions

unconventional interaction between the molecular

along the cut at Г and M points (Г–M direction) are

ferromagnetic layers and inorganic superconducting

presented, respectively. Of note, an electron pocket is

layers in the superlattice. These data clearly show the

observed at around M point, revealing the Fermi level

coexistence of superconductivity and ferromagnetism in

(EF) crossed the conduction band since ARPES could

the SnSe2-Co(Cp)2 superlattice nanoflakes.

only measure the band dispersions below Fermi

observed

and

Kondo

ferromagneticsm,

effect,

we

and

propose

interactions

framework,


between

which

is

confined

responsible

Co(Cp)2 for

the

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2D electron system. As a consequence, superconducting state

was

triggered

at

low

temperature,

which

established a semiconductor-superconductor transition in the SnSe2-Co(Cp)2 superlattice. In order to detect the origin of the ferromagnetic state occurring in SnSe2-Co(Cp)2 superlattice. Electron spin resonance (ESR) spectra were performed. As shown in Figure 7a, it can be seen that the spectrum of pristine SnSe2 crystal presents no ESR signal in the measured interval owing to its nonmagnetic ground state. For the pure Co(Cp)2 sample, a broad signal is observed at the magnetic field of about 250 mT (indicated by black arrow), which originate from the low spin state of Co2+ ions in Co(Cp)2 molecules. In addition, there is a sharp signal at 323 mT in the pure Co(Cp)2 spectrum guided by emerging

the red arrow, which is assigned to cyclopentadienyl. Of

superconductivity in SnSe2-Co(Cp)2 superlattice. (a)

note, the signal of cyclopentadienyl disappears in the

Figure

6.

Mechanism

of

the

Band structure of SnSe2-Co(Cp)2 superlattice revealed by ARPES. (b) Schematic of the Fermi level lift of SnSe2 after Co(Cp)2 intercalation. (c) Schematic illustration of charge transfer of Co(Cp)2 molecules confined in SnSe2-Co(Cp)2 superlattice.

surface47,48. As a typical semiconducting material, the EF of pristine SnSe2 is below the conduction band bottom (CBB) and above the valence band top49. From the ARPES at M point of our obtained SnSe2-Co(Cp)2 superlattice, it can be concluded that the EF moved upwards over CBB, indicating increased electron filling after the Co(Cp)2 molecules intercalation to form the superlattice as illustrated in Figure 6b. It is known that superconducting

transition

non-superconducting

can

materials

be by

induced tuning

in their

charge-carrier concentration50-54. In our case, it should be noted that the Co(Cp)2 molecule has two aromatic cyclopentadienyls with strong electron-donating ability. After the intercalation, the Co(Cp)2 molecules bonding

Figure

on the SnSe2 lattice resulted in interfacial coupling

SnSe2-Co(Cp)2 superlattice. (a) Electron spin resonance

7.

effects and led to electron transfer from Co(Cp)2

(ESR) spectra of pristine SnSe2, Co(Cp)2 precursor and

molecules to SnSe2 layers (Figure 6c). Upon electron

SnSe2-Co(Cp)2 superlattice, respectively. (b) Spin-state

doping, the EF shifts up across conduction band, so that

transition of Co(Cp)2 molecules confined in SnSe2

the CBB can be directly measured by ARPES. The shift of

interlayer. (c) Schematic illustration of the Co(Cp)2

EF is accompanied by a large increase of the density of

molecules confined in SnSe2 interlayer with high spin

states near Fermi surface, which created a high-density

state.

Mechanism


of

ferromagnetism

in


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SnSe2-Co(Cp)2 superlattice spectrum. And, a new signal is resolved at magnetic field of about 150 mT as marked by the blue arrow, which is corresponding to Co2+ ions with high spin state. In this case, confined space weakens coordination field of Co(Cp)2 molecules, leading to high spin state. In this regard, combining the above charge transfer process, it suggests that the disappearance of cyclopentadienyl signal is due to the electron transfer from cyclopentadienyls to SnSe2 layer. On the other hand, for the ferromagnetic state of SnSe2-Co(Cp)2 superlattice, it can be determined that the ferromagnetism is attributed to the spin-state transition of Co(Cp)2 molecules from low spin state to high spin state after confined in SnSe2 van der Waals gap (Figure 7b). In a word, the results of ARPES and the ESR revealed that electron transfer from cyclopentadienyls of Co(Cp)2

molecules

to

SnSe2

layer

triggered

the

superconducting state; and in the meanwhile, the high spin

state

of

confined

Co(Cp)2

molecules

was

Page 8 of 11

EXPERIMENTAL SECTION Synthesis of SnSe2 crystal and organic-inorganic SnSe2-Co(Cp)2 superlattice. SnSe2 single-crystal flakes were prepared via chemical vapor transport (CVT) with iodine used as transport agent. A mixture of Sn, Se and I2 powder was encapsulated in quartz tube with vaccum and the tube was placed into a two-zone temperature gradient furnace. The high-temperature side was kept at 800 °C while the low-temperature side at 700 °C for one day, and both lowered to room temperature in two days. Then the as-synthesized SnSe2 crystals were immersed in a 0.05M acetonitrile solution of Co(Cp)2 in quartz tube. The tube was froze with liquid nitrogen to avoid solvent volatilization and encapsulated with vacuum. Subsequently, the quartz tube was heated at 120 °C for one week. Finally, the SnSe2-Co(Cp)2 superlattice was obtained and washed with acetonitrile and ethanol for several times.

responsible to the emergence of ferromagnetism in

STM

SnSe2-Co(Cp)2 superlattice (Figure 7c).

microscopy (STM) measurements, SnSe2 crystal and

conclusion,

report

a

molecule-confined

chemical design, bringing the first case of freestanding coexistence of superconductivity and ferromagnetism non-superconducting

and

non-ferromagnetic

building blocks. Spatially-confined effect occurs when Co(Cp)2 molecules intercalated into layered SnSe2 forming 2D organic-inorganic superlattice. Spatially confinement effect weakens coordination field of Co(Cp)2

molecules,

leading

to

high

spin

with

ferromagnetic state; and cyclopentadienyls of Co(Cp)2 molecules

scanning

tunneling

the fresh surface under an ultrahigh vacuum. STM we

engineering in 2D organic-inorganic superlattice using a

with

For

SnSe2-Co(Cp)2 superlattice were cleaved in situ to obtain

CONCLUSIONS In

measurements.

strongly

couple

with

Se-Sn-Se

lattice,

measurements were performed at 70 K. ARPES measurements. Angle resolved photoemission spectroscopy (ARPES) experiments were performed with 23 eV photos at the beamline 13U of the National Synchrotron Radiation Laboratory (NSRL) at Hefei, China, using a Scienta R4000 electron spectrometer. The angular resolution was 0.3 degrees and the combined instrumental energy resolution was better than 20 meV. All samples were cleaved in situ and measured at 12 K under a vacuum better than 5×10−11 mbar. ASSOCIATED CONTENT

inducing electron transfer to trigger superconductivity.

Supporting Information

This entirely new class of coexisting superconductivity

TEM image, magnetic measurements, optical image of

and

correlated

electrode and other additional information. This

behaviour of Kondo effect, revealing an unconventional

material is available free of charge via the Internet at

interaction between the molecular ferromagnetic layers

http://pubs.acs.org.

and

ferromagnetism

inorganic

generates

superconducting

unique

layers.

Confined

molecular chemistry opens the way to incorporate

AUTHOR INFORMATION

unique benefits of molecules and low-dimensional host

Corresponding Author

matrices for exotic properties.

[email protected]


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Author Contributions § These authors contributed equally to this work. Notes The authors declare no competing financial interests. Acknowledgements This work was financially supported by the National Basic Research Program of China (2015CB932302), the National Natural Science Foundation of China (U1432133, 11621063, 51702311), National Program for Support of Top-notch Young Professionals, the Fundamental Research Funds for the Central Universities (No. WK 2060190084), the China Postdoctoral Science Foundation (Grant No. 2016M600483, 2017T100451). We would like to thank Dr. Yuyan Han (High Magnetic Field Laboratory, CAS) and Dr. Jiyin Zhao (USTC) for assistance with measurements of Physical Property Measurement System. We thank Professor Wensheng Yan (National Synchrotron Radiation Laboratory, USTC) for assistance with measurements of angle-dependent XANES. We also appreciate the support from the Major/Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology. This work was partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication. REFERENCES (1) Prakash, O.; Kumar, A.; Thamizhavel, A.; Ramakrishnan, S. Science 2017, 355, 52-55. (2) Wang, Z.; He, C.; Wu, S.; Tang, Z.; Liu, Y.; Ablimit, A.; Feng, C.; Cao, G. J. Am. Chem. Soc. 2016, 138, 7856-7859. (3) Sei, R.; Kitani, S.; Fukumura, T.; Kawaji, H.; Hasegawa, T. J. Am. Chem. Soc. 2016, 138, 11085-11088. (4) Xu, C.; Wang, L.; Liu, Z.; Chen, L.; Guo, J.; Kang, N.; Ma, X.; Cheng, H.; Ren, W. Nat. Mater. 2015, 14, 1135-1141. (5) Mitrano, M.; Cantaluppi, A.; Nicoletti, D.; Kaiser, S.; Perucchi, A.; Lupi, S.; Di Pietro, P.; Pontiroli, D.; Riccò, M.; Clark, S. R.; Jaksch, D.; Cavalleri, A. Nature 2016, 530, 461-464. (6) Pan, J.; Guo, C.; Song, C.; Lai, X.; Li, H.; Zhao, W.; Zhang, H.; Mu, G.; Bu, K.; Lin, T.; Xie, X.; Chen, M.; Huang, F. J. Am. Chem. Soc. 2017, 139, 4623-4626. (7) Ginzburg, V. L. Sov. Phys. JETP 1957, 4, 153–161. (8) Maple, M. B.; Fischer, Ø. Magnetic Superconductors. In Superconductivity in Ternary Compounds II. Maple, M. B.; Fischer, Ø., Eds. Springer Berlin Heidelberg: Berlin, Heidelberg, 1982, pp 1-10. (9) Fulde, P.; Ferrell, R. A. Phys. Rev. 1964, 135, A550-A563. (10) Larkin, A.; Ovchinnikov, I. Sov. Phys.-JETP 1965, 20, 762-769. (11) Wolowiec, C. T.; White, B. D.; Maple, M. B. Physica C 2015, 514, 113-129. (12) Bohnenbuck, B.; Zegkinoglou, I.; Strempfer, J.; Nelson, C. S.; Wu, H. H.; Schüßler-Langeheine, C.;

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Molecule-Confined Engineering toward Superconductivity and

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