crystal x-ray diffraction, we found
thatR,R- 1 andS,S-2are iso-
structural to the dysprosium ana-
log ( 28 ). The two enantiomers
crystallized in the polar space
groupP 21 with two independent
homochiral dinuclear complexes
within the asymmetric unit (Fig.
1andfigs.S2andS3).Thesetwo
complexes exhibit differences in
the crystallographic distances
and geometries (tables S1 and
S2) that give rise to uncom-
pensated dipolar moments along
thebaxis. We confirmed this by
analyzing the location of the
ions in the unit cell (table S3)
( 29 – 31 ).
We corroborated the enan-
tiomeric nature ofR,R- 1 andS,
S- 2 using solid-state circular
dichroism (CD) (fig. S4), with the
mirror-symmetrical CD spectra
showing Cotton effects of op-
posite signs at maximum wave-
lengths (lmax)of261,303,and
386 nm. The presence of the zinc
complex also acted as a sensitizer
toward lanthanide ions. Hence,
the complexesR,R- 1 andS,S-
2 showed the typical Yb3+lumi-
nescence in the 925- to 1075-nm
near-infrared region at both
room and low temperatures (figs.
S5 to S11) ( 32 ).
We verified the absence of
solvent molecules with thermo-
gravimetric analysis, which also
indicated that both enantiomers
remain stable up to 550 K (fig.
S12). We used single-crystal x-ray
diffraction at 400 K and differ-
ential scanning calorimetry to
confirm the absence of a phase
transition up to the decompo-
sition temperature (fig. S13). This
demonstrated that the material
remains crystallized in theP (^21)
polar space group. We inves-
tigated the magnetic proper-
ties ofR,R-1andS,S-2using
SQUID (superconducting quan-
tum interference device) mag-
netometry. We confirmed the
paramagnetic behavior expected
for a single Yb3+ion with a^2 F7/2
ground state (total angular mo-
mentJ= 7/2; orbital moment
L=3;spinmomentS=1/2)and
a room-temperature magnetic
moment close to 4.32 bohr
magnetons (fig. S14). We also
observed a typical slow relax-
ation of the magnetization at
Longet al.,Science 367 , 671–676 (2020) 7 February 2020 2of5
Fig. 2. Scanning probe microscopy (SPM) measurements of the (0 1 1)-orientedR,R-1 single crystal.(A)AFM
topography of theð 0 1 1 Þplane. (B) OOP (left) and IP (right) PFM responses without electrical bias. The color
mapping reveals a distinctive organization demonstrating the presence of spontaneously polarized domains of
opposite polarization states (shown in red and blue). (C) Magnified (×3) part of the scanned area [marked with
a dashed square in (A) and (B)] with the OOP (left) and IP (right) PFM responses at 0 V. (D) OOP (left) and
IP (right) PFM responses measured for the same area after the direct current (dc) bias voltage (±30 V) poling.
(E) Schematic of the PFM experiment. DFL, deflection;E, electric field.
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