CEMS Topical Meeting Online
Interplay between Chirality and Magnetism

TimetableandAbstracts

TimetableTime

13:00

Speaker
Daigo Miyajima (RIKENCEMS)

13:10 Hiroshi Yamamoto (IMS)

13:55

14:40

Kouta Kondou (RIKEN
CEMS)

Title of the Talk

Opening
Chirality-Induced Spin Selectivity in an
Organic Superconductor
Observation of Chirality Induced
Magnetoresistance Due toThermally
Driven Spin Polarization

Tetsuaki Itou (Tokyo

Current-Induced Magnetization in

University of Science)

Elemental Tellurium

15:25 Closing

15:40

16:25

Kouji Taniguchi (TohokuUniversity)
Masayuki Suda (KyotoUniversity)

17:10 Closing

Optical responses coupled with spins in
the chirality-introduced layered organicinorganic hybrid perovskites
Novel Hybrid Chiral Mateirlas for Spinpolarized Charge Transport and Spindependent Electrocatalytic Applications

Chirality-Induced Spin Selectivity in an Organic Superconductor
Hiroshi M. Yamamoto
Institute for Molecular Science, Okazaki, Japan
Chirality-Induced Spin Selectivity (CISS) effect is attracting recent attention as a new source of spinpolarized current. Through this effect, chiral molecules can sometimes generate electrical currents
whose spins are highly oriented depending on the molecular handedness and the current direction. It
also provides unique methods for enantio-separation, enantio-selective electrochemical reactions, andan efficient water oxidation. The mechanism of CISS effect is, however, yet to be clarified, as theeffect is much larger than expected one estimated by normal theoretical investigation based on a small
spin-orbit coupling for light elements. In a hypothetical consideration, it is proposed that anenhancement of spin polarization is based on anti-parallel spin polarizations at two opposite ends of achiral molecule created in a non-equilibrium condition.
In our experiment, we have tried to confirm this hypothesis by using an organic chiral superconductor,
which has chiral crystal structure with coherent electrons, under electrical excitation. By measuringspin-dependent voltage drop created at nickel electrodes attached to the chiral superconductor, wehave successfully confirmed an enhanced spin accumulation exceeding the expectation from Edelsteineffect. Moreover, formation of a pair of antiparallel spin accumulations at two opposite ends of thesuperconducting crystal was confirmed, which further supports the above hypothesis.

Observation of chirality induced magnetoresistance due tothermally driven spin polarization
Kouta Kondou
RIKEN, Center for Emergent Matter Science (CEMS), Japan
Molecular chirality is an essential parameter for inducing spin functionalities in organic materials.
Indeed, the spin polarization of electrons passing through chiral molecules has been investigatedintensively since 20 years ago [1]. This feature is called the chiral induced spin selectivity (CISS) effect,
which has been confirmed using various experimental techniques [2]. Such a chiral molecule-induced
phenomenon should lead to the driving principle of nanoscale spin manipulation in the wide range of fields
such as spintronics, quantum computing, and biochemistry.
Recently, several experimental studies have reported that a chiral molecule could behave like a magnet[3-6]. In contrast to the previously reported CISS effect, no bias charge current flows through the molecule
implying that the magnetization, i.e., spontaneous spin polarization, might emerge in the chiral molecules.
Thus, here we experimentally demonstrate the CISS-related spontaneous spin polarization by means ofmagnetoresistance measurements. Figure shows the schematic illustration of chiral molecule induced
current-in-plane magnetoresistance (CIP-MR) [7]. By using the chiral molecule/ferromagnet bilayer, weobserved the chirality dependent CIP-MR, which does not require the bias charge current in the chiralmolecule. Moreover, the temperature dependence of the CIP-MR suggests thermally driven spontaneous
spin-polarization in the chiral molecules is the key for the observed MR.

Figure Schematic illustration of chiral-molecule induced current-in-planemagnetoresistance in chiral molecule/ferromagnet bilayer. Springs beside each chiralmolecule denote the helicity.

[1] K. Ray, S. P. Ananthavel, D. H. Waldeck, and R. Naaman, Science 283, 814 (1999).
[2] R. Naaman, Y. Paltiel, and D. H. Waldeck, Nature Reviews Chemistry 3, 250 (2019).
[3] O. Ben Dor et al., Nat Communications 8, 14567 (2017).
[4] H. Alpern et al., Nano Letter 19, 5167 (2019).
[5] S. Miwa, K. Kondou et al., Applied Physics Express 13, 113001 (2020).
[6] N. Goren, S. Yochelis, G. Jung, G. Y. Paltiel, Applied Physics Letters, 118 (17) (2021).
[7] K. Kondou et al. arXiv:2112.08607

Current-induced magnetization in elemental tellurium
Tetsuaki Itou
Department of Applied Physics, Tokyo University of Science
I will present our demonstration of current-induced bulk magnetization in trigonal tellurium[1]. From the viewpoint of symmetry, the current-induced bulk magnetization effect can beobserved in a system belonging to “gyrotropic” point groups, which include chiral(enantiomorphic) point groups, as shown in Fig. 1 [2]. Meeting this condition, trigonaltellurium consists of helical right-handed or left-handed chains of tellurium atoms in ahexagonal arrangement and belongs to the chiral point group D3.
We measured the 125Te NMR spectra of single crystals of p-type tellurium under an applied
pulsed electric current parallel to the c axis. We observed the current-induced shift of a125

Te-NMR spectrum depending on the strength and the polarity of an applied electric current.
We also observed that the current-induced NMR shift is reversed by a chirality reversal of thetellurium crystal structure. These results clearly indicate that an applied current induces bulk
electronic magnetization.

Fig 1. Possible second-rank axial tensor forms of the linear current-induced magnetization effectfor 21 noncentrosymmetric crystal point groups [2].

[1] T. Furukawa, Y. Shimokawa, K. Kobayashi, and T. Itou, Nat. Commun. 8, 954 (2017).
[2] T. Furukawa, Y. Watanabe, N. Ogasawara, K. Kobayashi, and T. Itou, Phys. Rev. Research 3,023111 (2021).

Optical responses coupled with spins in the chirality-introduced
layered organic-inorganic hybrid perovskites
Kouji Taniguchi
Institute for Materials Research, Tohoku University
2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
Organic-inorganic hybrid perovskite (OIHP)-type lead halides are recently attracting worldwide
interest as a photoelectric conversion material, such as a light absorber in the solar cell [1]. Herein,
we report the zero-bias photocurrent generating phenomena, such as bulk photogalvanic effect(BPVE) [2] and circular photogalvanic effect (CPGE) [3], and the nonreciprocal directional dichroism
induced by the optical magneto-electric effect (OME-effect) [4] in the noncentrosymmetric 2D-OIHP
metal halides, which are designed by incorporating organic chiral molecular cations between the
inorganic layers of metal halides. In particular, the CPGE originates from spin-polarized electronic
band structures in noncentrosymmetric systems with strong spin-orbit coupling (SOC) and isexpected as a fascinating opto-electronic effect, which might generate spin-polarized current only by
light irradiation without application of a bias voltage even in nonmagnetic systems. In our study, we
have observed light-helicity-dependent steady photocurrents induced by the CPGE and the chirality
dependent CPGE in the chiral 2D-OIHP lead iodides. These results indicate the formation of chirality
dependent radial spin texture in the k-space of chiral 2D-OIHPs with strong SOC. In addition, we
have also developed noncentrosymmetric ferromagnets in 2D-OIHPs based on the materials designconcept introducing chiral molecules into the inorganic layers. In the developed noncentrosymmetricferromagnetic copper chlorides, nonreciprocal directional dichroism has been induced by the OMEeffect. As demonstrated in our studies, OIHP-type compounds should be promising platforms for
opto-spintronics and magneto-optics applications in the future.

[1] A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, J. Am. Chem. Soc., 2009,131, 6050-6051.
[2] P.-J. Huang, K. Taniguchi, H. Miyasaka, J. Am. Chem. Soc., 2019,141, 14520-14523.
[3] P.-J. Huang, K. Taniguchi et al., Adv. Mater., 2021, 33, 2008611 (1)-(9).
[4] K. Taniguchi et al., Angew. Chem. Int. Ed.., 2021, 60, 14350-14354.

Novel Hybrid Chiral Materials for Spin-polarized Charge Transport and Spin-dependent
Electrocatalytic Applications

Masayuki Suda, Ph. D.
Kyoto University

Abstract:

The chiral-induced spin selectivity (CISS) effect enables the application of chiral organic
materials for spintronics and spin-dependent electrochemical applications. It has been
demonstrated on various chiral monolayers, in which their conversion efficiency is limited.
On the other hand, relatively high spin polarization (SP) rates are observed on bulk chiralmaterials; however, their poor electronic conductivities limit their application. In this study,
the design of organic-inorganic hybrid materials with a high SP rate and high conductivity isreported. Molecular chirality was introduced to the inorganic nanomaterials such as metal
nanoparitcles and transition metal dichalcogenides through the chemical reactions. This
design approach activated multiple tunneling channels in the chiral layers, which resulted ina SP rate as high as 75%. The synergistic effect has been demonstrated as an interplay of thehigh SP rate and the high conductivity or high catalytic activity on the performance of spindependent electrocatalysis. This novel approach employed in this work paves way for thedevelopment of other novel chiral systems for spintronics and spin-dependent
electrochemical applications.