Quantum Spin Liquid: In antiferromagnets, the lowest-energy state is reached when neighboring spins on the underlying lattice point in opposite directions. Because of geometric constraints on some lattices (such as the two-dimensional triangular lattice), this magnetic ordering cannot be achieved even at temperatures close to absolute zero, and these compounds are predicted to be in a quantum spin liquid state. Yamashita et al. (p. 1246 ) measured the thermal conductivity of a recently identified candidate quantum spin liquid, the organic compound EtMe ₃ Sb[Pd(dmit) ₂ ] ₂ , and characterized its lowest-lying excitations. Two types of excitations were observed: ballistically propagating gapless excitations and excitations associated with a finite spin gap. These results contribute to our understanding of this unusual state of matter, which is potentially relevant to other two-dimensional quantum systems.

Chirality-induced spin transport phenomena are investigated at room temperature without magnetic fields in a monoaxial chiral dichalcogenide ${\mathrm{CrNb}}_3{\mathrm{S}}_6$. We found that spin polarization occurs in these chiral bulk crystals under a charge current flowing along the principal $c$ axis. Such phenomena are detected as an inverse spin Hall signal which is induced on the detection electrode that absorbs polarized spin from the chiral crystal. The inverse response is observed when applying the charge current into the detection electrode. The signal sign reverses in the device with the opposite chirality. Furthermore, the spin signals are found over micrometer length scales in a nonlocal configuration. Such a robust generation and protection of the spin-polarized state is discussed based on a one-dimensional model with an antisymmetric spin-orbit coupling.

Artificial molecular switches and machines that enable the directional movements of molecular components by external stimuli have undergone rapid advances over the past several decades. Particularly, overcrowded alkene-based artificial molecular motors are highly attractive from the viewpoint of chirality switching during rotational steps. However, the integration of these molecular switches into solid-state devices is still challenging. Herein, we present an example of a solid-state spin-filtering device that can switch the spin polarization direction by light irradiation or thermal treatment. This device utilizes the chirality inversion of molecular motors as a light-driven reconfigurable spin filter owing to the chiral-induced spin selectivity effect. Through this device, we found that the flexibility at the molecular scale is essential for the electrodes in solid-state devices using molecular machines. The present results are beneficial to the development of solid-state functionalities emerging from nanosized motions of molecular switches.

A spin-polarized state is examined under charge current at room temperature without magnetic fields in chiral disilicide crystals ${\mathrm{NbSi}}_2$ and ${\mathrm{TaSi}}_2$. We found that a long-range spin transport occurs over ten micrometers in these inorganic crystals. A distribution of crystalline grains of different handedness is obtained via location-sensitive electrical transport measurements. The sum rule holds in the conversion coefficient in the current-voltage characteristics. A diamagnetic nature of the crystals supports that the spin polarization is not due to localized electron spins but due to itinerant electron spins. A large difference in the strength of antisymmetric spin-orbit interaction associated with $4d$ electrons in Nb and $5d$ ones in Ta is oppositely correlated with that of the spin polarization. A robust protection of the spin polarization occurs over long distances in chiral crystals.