Effective Hamiltonian model for helically constrained quantum systems within adiabatic perturbation theory: application to the Chirality-Induced Spin Selectivity (CISS) Effect
Matthias Geyer, Rafael Gutierrez, Gianaurelio Cuniberti
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 structure, such models can be considered a minimal setup for the description of spin-dependent effects. We use adiabatic perturbation theory to provide a mathematically sound approximation procedure applicable to a large class of spin-dependent continuum models. We take advantage of the models simplicity by analyzing its structure to gain a better understanding how the occurrence and magnitude of spin polarization effects relate to the model's parameters and geometry.
Organic materials are known to feature long spin-diffusion times, originating in a generally small spin-orbit coupling observed in these systems. From that perspective, chiral molecules acting as efficient spin selectors pose a puzzle, that attracted a lot of attention during the recent years. Here we revisit the physical origins of chiral-induced spin selectivity (CISS), and propose a simple analytic minimal model to describe it. The model treats a chiral molecule as an anisotropic wire with molecular dipole moments aligned arbitrarily with respect to the wire's axes, and is therefore quite g…
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…
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）
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…
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）
The observation of chiral-induced spin selectivity (CISS) in biological molecules still awaits a full theoretical explanation. In a recent Rapid Communication, Varela et al. [Phys. Rev. B 101, 241410(R) (2020)] presented a model for electron transport in biological molecules by tunneling in the presence of spin-orbit interactions. They then claimed that their model produces a strong spin asymmetry due to the intrinsic atomic spin-orbit strength. As their Hamiltonian is time-reversal symmetric, this result contradicts a theorem by Bardarson [J. Phys. A: Math. Theor. 41, 405203 (2008)], which st…
Various device-based experiments have indicated that electron transfer in certain chiral molecules may be spin-dependent, a phenomenon known as the Chiral Induced Spin Selectivity (CISS) effect. However, due to the complexity of these devices and a lack of theoretical understanding, it is not always clear to what extent the chiral character of the molecules actually contributes to the magnetic-field-dependent signals in these experiments. To address this issue, we report here an electron transmission model that evaluates the role of the CISS effect in two-terminal and multi-terminal linear-reg…
Understanding chiral induced spin-selectivity (CISS), resulting from charge transport through helical systems, has recently inspired many experimental and theoretical efforts, but is still object of intense debate. In order to assess the nature of CISS, we propose to focus on electron-transfer processes occurring at the single-molecule level. We design simple magnetic resonance experiments, exploiting a qubit as a highly sensitive and coherent magnetic sensor, to provide clear signatures of the acceptor polarization. Moreover, we show that information could even be obtained from time-resolved …
The chiral induced spin selectivity (CISS) in layers of helical molecules gained considerable attention in the emerging field of spintronics, because the effect enables spin-filter devices under ambient conditions. Several theoretical studies have been carried out to explain this effect on a microscopic scale, but the origin of the effect is still controversial. In particular the role of spin-flip scattering during electron transport is an open issue. In this study we describe the electron and spin transport by rate equations including spin-dependent losses and spin-flip scattering. We reduce …
Geometric Spin-Orbit Coupling Resolves the Contradictory CISS Effect in Chiral Single 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）
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…
Recent research discovered that charge transfer processes in chiral molecules can be spin selective and named the effect chiral-induced spin selectivity (CISS). Follow-up work studied hybrid spintronic devices with conventional electronic materials and chiral (bio)molecules. However, a theoretical foundation for the CISS effect is still in development and the spintronic signals were not evaluated quantitatively. We present a circuit-model approach that can provide quantitative evaluations. Our analysis assumes the scheme of a recent experiment that used photosystem~I (PSI) as spin injectors, f…
Chiral-induced spin selectivity (CISS) is a phenomenon in which electron spins are polarized as they are transported through chiral molecules, and the spin polarization depends on the handedness of the chiral molecule. In this study, we show that spin selectivity can be realized in achiral materials by coupling electrons to a single mode of a chiral optical cavity. By investigating spin-dependent electron transport using the nonequilibrium Green's function approach, the spin polarization in a two-terminal setup is demonstrated to approach unity if the rate of dephasing is sufficiently small an…
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 spin-selective transport through helical molecules has been a hot topic in condensed matter physics, because it develops a new research direction in spintronics, \emph{i.e.}, chiro-spintronics. Double-stranded DNA (dsDNA) molecules have been considered as promising candidates to study this topic, since the chiral-induced spin selectivity (CISS) effect in dsDNA was observed in experiment. Considering that the dsDNA molecules are usually flexible in mechanical properties, vibration may be one of important factors to influence the CISS effect. Here, we investigate the influences of electron-v…
The chirality-induced spin selectivity (CISS) effect enables the detection of chirality as electrical charge signals. It is often studied using a two-terminal circuit geometry where a ferromagnet is connected to a chiral component, and a change of electrical resistance is reported upon magnetization reversal. This is however not expected in the linear response regime because of compensating reciprocal processes, limiting the interpretation of experimental results. Here we show that magnetoresistance effects can indeed appear even in the linear response regime, either by changing the magnitude …
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）
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 …
Chiral-induced spin selectivity (CISS), whereby helical molecules polarize the spin of electrical current, is an intriguing effect with potential applications in nanospintronics. In this nascent field, the study of paramagnetic chiral molecules, which could introduce another degree of freedom in the control of the spin transport, remains so far unexplored. To address this challenge, herein, we propose the use of self-assembled monolayers of helical lanthanide-binding peptides. In order to elucidate the effect of the paramagnetic nuclei, monolayers of the peptide coordinating paramagnetic or di…
Max-Born-Institut（马克斯·博恩研究所）；Insitute of Physics, Humboldt University zu Berlin（柏林洪堡大学物理研究所）；Technion - Israel Institute of Technology（以色列理工学院）；School of Molecular Sciences, Arizona State University（亚利桑那州立大学分子科学学院）；Department of Physics, Imperial College London（伦敦帝国理工学院物理系）；Department of Physics, Freie Universität Berlin（柏林自由大学物理系）；Technische Universität Berlin（柏林工业大学）
