Three-Dimensional Near-Surface Imaging of Chirality Domains with Circularly Polarized X-rays

Chiroptical Activity in All-Inorganic Intrinsically Chiral Perovskite-like Nanocrystals Synthesized via Enantioselective Strategy

Enantiomeric control of intrinsically chiral inorganic nanocrystals (NCs), despite being reported in few systems over the past years, still remains a challenging task. Here, we succeeded in the enantioselective synthesis of intrinsically chiral perovskite-like CsCuCl₃ NCs in the presence of chiral amino acids using an antisolvent crystallization method at room temperature. The d-/l-ligand-induced enantiomeric NCs showed the relevant characteristic chiroptical responses. Interestingly, under the addition of each d- or l-form of the ligand, the chiroptical activity of the NCs could be tailored through facilely tuning the Cs/Cu feed ratios and amino acid types. The polarity of such amino acids and their coordination configurations with the NC structures contributed to the distinct behaviors. The ability to manipulate the ligand-induced enantioselective strategy would open pathways for the controllable synthesis of intrinsically chiral inorganics and enable a better understanding of the origins of precursor-ligand-associated chiral discrimination and crystallization phenomena.

Spin selectivity in chiral metal-halide semiconductors

Controlling the spin states of freedom represents a significant challenge for the next-generation optoelectronic and spintronic devices. Chiral metal-halide semiconductors (MHS) have recently emerged as an important class of materials for spin-dependent photonic and electronic applications. In this Minireview, we first discussed the chemical and structural diversity of chiral MHS, highlighting the chirality formation mechanism. We then provided our current understanding on the spin-sensitive photophysical and transport process with a focus on how chirality enables the spin selectivity in chiral MHS. We summarized recent progress on the experimental demonstration of spin control in various photonic and spintronic devices. Finally, we discussed ongoing challenges and opportunities associated with chiral MHS.

X-ray Natural Circular Dichroism Imaging of Multiferroic Crystals

The polarizing spectroscopy techniques in visible range optics have been used since the beginning of the 20th century to study the anisotropy of crystals based on birefringence and optical activity phenomena. On the other hand, the phenomenon of X-ray optical activity has been demonstrated only relatively recently. It is a selective probe for the element-specific properties of individual atoms in non-centrosymmetric materials. We report the X-ray Natural Circular Dichroism (XNCD) imaging technique which enables spatially resolved mapping of X-ray optical activity in non-centrosymmetric materials. As an example, we present the results of combining micro-focusing X-ray optics with circularly polarized hard X-rays to make a map of enantiomorphous twinning in a multiferroic SmFe3(BO3)4 crystal. Our results demonstrate the utility and potential of polarization-contrast imaging with XNCD as a sensitive technique for multiferroic crystals where the local enantiomorphous properties are especially important. In perspective, this brings a novel high-performance method for the characterization of structural changes associated with phase transitions and identification of the size and spatial distribution of twin domains.

All-in-all-out magnetic domains: x-ray diffraction imaging and magnetic field control

Long-range noncollinear all-in-all-out magnetic order has been directly observed for the first time in real space in the pyrochlore Cd_{2}Os_{2}O_{7} using resonant magnetic microdiffraction at the Os L_{3} edge. Two different antiferromagnetic domains related by time-reversal symmetry could be distinguished and have been mapped within the same single crystal. The two types of domains are akin to magnetic twins and were expected-yet unobserved so far-in the all-in-all-out model. Even though the magnetic domains are antiferromagnetic, we show that their distribution can be controlled using a magnetic field-cooling procedure.