Electron exchange and correlations emerging from the coupling between ionic vibrations and electrons are addressed. Spin-dependent electron-phonon coupling originates from the spin-orbit interaction, and it is shown that such electron-phonon coupling introduces exchange splitting between the spin channels in the structure. By application of these results to a model for a chiral molecular structure mounted between metallic leads, the chirality induced spin selectivity is found to become several tens of percents using experimentally feasible parameters.
We report a new type of spin-orbit coupling (SOC) called geometric SOC. Starting from the relativistic theory in curved space, we derive an effective nonrelativistic Hamiltonian in a generic curve embedded into flat three dimensions. The geometric SOC is $O(m^{-1})$, in which $m$ is the electron mass, and hence much larger than the conventional SOC of $O(m^{-2})$. The energy scale is estimated to be a hundred meV for a nanoscale helix. We calculate the current-induced spin polarization in a coupled-helix model as a representative of the chirality-induced spin selectivity. We find that it depen…
Chirality induced spin selectivity, discovered about two decades ago in helical molecules, is a non-equilibrium effect that emerges from the interplay between geometrical helicity and spin-orbit interactions. Several model Hamiltonians building on this interplay have been proposed and while these can yield spin-polarized transport properties that agrees with experimental observations, they simultaneously depend on unrealistic values of the spin-orbit interaction parameters. It is likely, however, that a common deficit originates from the fact that all these models are uncorrelated, or, single-…
The chirality-induced spin selectivity (CISS) effect gives rise to strongly spin-dependent transport through many organic molecules and structures. Its discovery raises fascinating fundamental questions as well as the prospect of possible applications. The basic phenomenology, a strongly asymmetric magnetoresistance despite the absence of magnetism, is now understood to result from the combination of spin-orbit coupling and chiral geometry. However, experimental signatures of electronic helicity were observed at room temperature, i.e., at an energy scale that exceeds the typical spin-orbit cou…
The elucidation of the mechanisms behind chiral-induced spin selectivity remains an outstanding scientific challenge. Here we consider the role of delocalised phonon modes in electron transport in chiral structures and demonstrate that spin selectivity can originate from spin-dependent energy and momentum conservation in electron-phonon scattering events. While this mechanism is robust to the specifical nature of the vibrational modes, the degree of spin polarization depends on environmental factors, such as external driving fields, temperatures and phonon relaxation rates. This dependence is …
The chirality-induced spin selectivity (CISS) effect has been confirmed experimentally for a large class of organic molecules. Adequately modeling the effect remains a challenging task, with both phenomenological models and first-principle simulations yielding inconclusive results. Building upon a previously presented model by K. Michaeli and R. Naaman (J. Phys. Chem C 123, 17043 (2019)) we systematically investigate an effective 1-dimensional model derived as the limit of a 3-dimensional quantum system with strong confinement and including spin-orbit coupling. Having a simple analytic structu…
Symmetry considerations in chirality-induced spin selectivity
Helmholtz-Institut Mainz（亥姆霍兹美因茨研究所）；GSI Helmholtzzentrum für Schwerionenforschung GmbH（GSI重离子研究中心有限公司）；QUANTUM, Institut für Physik, Johannes Gutenberg-Universität（约翰内斯·古腾堡大学量子物理研究所）；Department of Physics, University of California（加州大学物理系）；Institute of Physics, Johannes Gutenberg-University Mainz（约翰内斯·古腾堡大学美因茨分校物理研究所）
Here we propose a mechanism by which spin polarization can be generated dynamically in chiral molecular systems undergoing photo-induced electron transfer. The proposed mechanism explains how spin polarization emerges in systems where charge transport is dominated by incoherent hopping, mediated by spin orbit and electronic exchange couplings through an intermediate charge transfer state. We derive a simple expression for the spin polarization that predicts a non-monotonic temperature dependence consistent with recent experiments. We validate this theory using approximate quantum master equati…
Chirality-induced spin selectivity (CISS) refers to the fact that electrons get spin polarized after passing through organic chiral molecules in a nanoscale device. In CISS, chiral molecules are commonly believed to be a spin filter through which one favored spin transmits and the opposite spin gets reflected, i.e., transmitted and reflected electrons exhibit opposite spin polarization. In this work, we point out that such a spin filter scenario contradicts the principle that equilibrium spin current must vanish. Instead, we find that both transmitted and reflected electrons present the same t…
Real Space Imaging of Spin Scattering in Chirality-Induced Spin Selectivity
Ulsan National Institute of Science and Technology (UNIST)（蔚山科学技术院）；Weizmann Institute of Science（魏茨曼科学研究所）；Pennsylvania State University（宾夕法尼亚州立大学）；Max Planck Institute for the Structure and Dynamics of Matter（物质结构与动力学马普研究所）
Chirality-induced spin selectivity without intrinsic spin-orbit coupling: Role of current-induced molecular orbital moment
The Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所）；Institute of Physics, Johannes Gutenberg-University（约翰内斯·古腾堡大学物理研究所）；Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich GmbH（于利希研究中心彼得·格林伯格研究所（PGI-6））
What Is the Real-Time Atomistic Mechanism Behind Chirality-Induced Spin Selectivity in Donor-Chiral Bridge-Acceptor Molecules?
School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology（华中科技大学物理学院与武汉国家强磁场中心）；Institute for Quantum Science and Engineering, Huazhong University of Science and Technology（华中科技大学量子科学与工程研究院）
Emergent chirality and enantiomeric selectivity in layered NbOX$_2$ crystals
Aalto University（阿尔托大学）；Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Centro de Física de Materiales (CFM-MPC), CSIC-UPV/EHU（材料物理中心，西班牙国家研究委员会-巴斯克国立大学）；University of the Basque Country (UPV/EHU)（巴斯克国立大学）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）；Université de Sherbrooke（舍布鲁克大学）；Regroupement Québécois sur les Matériaux de Pointe (RQMP)（魁北克尖端材料联盟）
研究层状NbOX₂晶体的结构和电子性质，揭示其非手性I m m m相与手性C2相之间的联系，通过原理计算发现中间非手性C2/m相，并探讨电场和压力对手性稳定的影响。
A minimal model is exactly solved for electron spin transport on a helix. Electron transport is assumed to be supported by well oriented $p_z$ type orbitals on base molecules forming a staircase of definite chirality. In a tight binding interpretation, the SOC opens up an effective $π_z-π_z$ coupling via interbase $p_{x,y}-p_z$ hopping, introducing spin coupled transport. The resulting continuum model spectrum shows two Kramers doublet transport channels with a gap proportional to the SOC. Each doubly degenerate channel satisfies time reversal symmetry, nevertheless, a bias chooses a transport…
Central to spintronics is the interconversion between electronic charge and spin currents, and this can arise from the chirality-induced spin selectivity (CISS) effect. CISS is often studied as magnetoresistance (MR) in two-terminal (2T) electronic devices containing a chiral (molecular) component and a ferromagnet. However, fundamental understanding of when and how this MR can occur is lacking. Here, we uncover an elementary mechanism that generates such a MR for nonlinear response. It requires energy-dependent transport and energy relaxation within the device. The sign of the MR depends on c…
The theoretical explanation for the chiral-induced spin selectivity effect, in which electrons' passage through a chiral system depends on their spin and the handedness of the system, remains vague. Although most experimental work was performed at room temperature, most of the proposed theories did not include vibrations. Here, we present temperature-dependent experiments and a theoretical model that captures all observations and provides spin polarization values that are consistent with the experimental results. The model includes vibrational contribution to the spin orbit coupling. It shows …
Chiral induced spin selectivity is a phenomenon that has been attributed to chirality, spin-orbit interactions, and non-equilibrium conditions, while the role of electron exchange and correlations have been investigated only marginally until very recently. However, as recent experiments show that chiral molecules acquire a finite spin-polarization merely by being in contact with a metallic surface, these results suggest that electron correlations play a more crucial role for the emergence of the phenomenon than previously thought. Here, it is demonstrated that molecular vibrations give rise to…
Topological aspects of the geometry of DNA and similar chiral molecules have received a lot of attention, while the topology of their electronic structure is less explored. Previous experiments have revealed that DNA can efficiently filter spin-polarized electrons between metal contacts, a process called chiral-induced spin-selectivity (CISS). However, the underlying correlation between chiral structure and electronic spin remains elusive. In this work, we reveal an orbital texture in the band structure, a topological characteristic induced by the chirality. We find that this orbital texture e…
Time-reversal symmetric charge and spin transport through a molecule comprising two-orbital channels and connected to two leads is analyzed. It is demonstrated that spin-resolved currents are generated when spin-flip processes are accompanied by a flip of the orbital channels. This surprising finding does not contradict Bardarson's theorem [J. H. Bardarson, J. Phys. A: Math. Theor. 41, 405203 (2008)] for two-terminal junctions: the transmission does possess two pairs of doubly-degenerate eigenvalues as required by the theorem. The spin-filtering effect is explicitly demonstrated for a two-term…
The helical distribution of the electronic density in chiral molecules, such as DNA and bacteriorhodopsin, has been suggested to induce a spin-orbit coupling interaction that may lead to the so-called chirality-induced spin selectivity (CISS) effect. Key ingredients for the theoretical modelling are, in this context, the helically shaped potential of the molecule and, concomitantly, a Rashba-like spin-orbit coupling due to the appearance of a magnetic field in the electron reference frame. Symmetries of these models clearly play a crucial role in explaining the observed effect, but a thorough …
We report chirality-induced current-in-plane magnetoresistance (CIP-MR) in chiral molecule/ferromagnetic metal bilayer at room temperature. The previously reported chiralityinduced current-perpendicular-to-plane magnetoresistance (CPP-MR) originates from the chiral induced spin-selectivity (CISS) effect that needs charge-current passing through the molecule. In contrast, the observed CIP-MR in the present study requires no bias charge current through the molecule. The temperature dependence of CIP-MR suggests thermally induced spin-polarization in the chiral molecules is the key for the observ…
