arXiv subjects

Tian-Yi Zhang

Publications and source records attributed to Tian-Yi Zhang.

9 recordsLinked to original sources

arXiv2026

Spin-to-charge conversion driven by inverse chiral-induced spin selectivity

Chiral molecules have attracted significant multidisciplinary interest and extensive research owing to their remarkable ability to achieve charge-to-spin conversion, known as the chiral-induced spin selectivity (CISS). A recent experiment has revealed that chiral molecules also exhibit an unexpected capability for spin-to-charge conversion, referred to as the inverse CISS (ICISS), opening unprecedented avenues for the study and application of chiral molecules. Here, we propose a theoretical model, suggesting that ICISS can be understood in terms of spin-dependent electron deflection induced by the interplay between spin and chiral structure. Our numerical results are consistent with experimental observations, demonstrating that ICISS persists under strong disorder. Our model also reproduces the inverse spin Hall effect (ISHE) in this experiment. Comparative analysis indicates that ICISS exhibits a spin-to-charge conversion behavior that differs from ISHE. Our work develops a microscopic theoretical model that accounts for the experimentally observed phenomena, and may provide a useful perspective for organic spintronics.

physics.chem-ph↗

arXiv2026

Unconventional Spin Valve Based on Normal Metal/Chiral Molecule/Altermagnet Junctions

Chiral molecules have attracted broad interdisciplinary interest for their ability to produce highly spin-polarized current. This phenomenon, known as the chiral-induced spin selectivity effect, holds great potential in the field of spintronics. Here, we propose to combine chiral molecules with altermagnets to construct highly efficient and tunable spin valves. Using the nonequilibrium Green's function method and the Landauer-Büttiker formula, we obtain the conductance and the magnetoresistance of a normal metal/chiral molecule/altermagnet spin valve. Our theoretical results reveal that the conductance of the spin valve can be effectively tuned by reorienting the Néel vector of the altermagnet, and the magnetoresistance of the spin valve increases with molecular length and altermagnetic anisotropy. Moreover, the magnetoresistance vanishes for achiral molecules or in the absence of molecular spin-orbit coupling. Our work paves the way for developing efficient, controllable, and stray-field-free spintronic devices.

physics.chem-ph↗

arXiv2026

HyCE-RAG: Hypergraph Chain-of-Evidence Retrieval-Augmented Generation for Explainable Multi-hop Question Answering

Multi-hop question answering requires systems to retrieve evidence from multiple documents and connect scattered facts into a coherent reasoning process. Standard retrieval-augmented generation (RAG) mainly relies on semantic similarity between a query and text chunks, and therefore often fails to model structural relations among entities, facts, and evidence units. Graph-based RAG improves this by introducing graph-structured knowledge, but pairwise edges are still limited in representing higher-order associations involving multiple entities and contexts. We propose HyCE-RAG, a Hypergraph Chain-of-Evidence Retrieval-Augmented Generation framework for explainable multi-hop question answering. HyCE-RAG organizes entities, relations, and contextual evidence into hyperedges, builds a query-aware evidence hypergraph, and performs confidence propagation over entity--hyperedge incidence structures. It then uses confidence-guided evidence assembly to select, connect, and rank evidence paths before answer generation. The scoring process jointly considers semantic relevance, entity connectivity, evidence coverage, relation reliability, extraction confidence, and propagated confidence. By providing the language model with structured evidence chains rather than flat retrieved passages, HyCE-RAG supports more faithful and interpretable reasoning. Experiments on HotpotQA, 2WikiMultihopQA, MuSiQue, and two GraphRAG-Bench subsets show that HyCE-RAG consistently outperforms standard RAG and graph-based RAG baselines in answer accuracy, context relevance, and faithfulness. These results suggest that hypergraph-based evidence organization is a promising direction for post-retrieval reasoning in complex question answering.

cs.AI↗

arXiv2026

HyperWorld: Hypergraph-Structured State Serialization Improves Learned Textual World Models

World models enable language-model agents to predict environment dynamics and plan before acting. In text environments, the model must learn symbolic action effects from serialized state descriptions, but the role of serialization structure remains underexplored. We present HyperWorld, a controlled study of state serialization for learned textual world models. We compare raw observations with three symbolic serializations of the same ground-truth state: independent sentences, pairwise triples, and entity-centered hyperedge units that group multiple related facts around entities and relations. All variants use the same training objective: given a state and an action, predict symbolic effects or judge the action infeasible. Across model scales, data budgets, and in-distribution and out-of-distribution test worlds, hyperedge serialization gives the clearest gains for 0.5B--1.5B models and under distribution shift. Larger models reduce the gap, and pairwise triples can match or slightly exceed hyperedges on in-distribution exact match, but hyperedges achieve the strongest out-of-distribution fact F1 and the best small-to-medium scale trade-off between feasibility detection and effect prediction. In downstream greedy planning, the hyperedge world model also attains the highest success rate among the tested representations. These results show that higher-order state organization is a simple but effective inductive bias for learned symbolic world models, especially when model capacity is limited or test environments differ from training.

cs.AI↗

arXiv2026

Engineering chiral-induced spin selectivity in an artificial topological quantum well

Chiral-induced spin selectivity (CISS) is a striking phenomenon in which spin-unpolarized electrons become spin-polarized after traversing a chiral medium. Theoretical studies have shown that spin-orbit coupling, geometric chirality, and dephasing act cooperatively for this effect to emerge. Inspired by this, we demonstrate a solid-state realization of CISS in an engineered InAs/GaSb quantum well where geometric chirality and dephasing can be introduced controllably. Introducing a chiral structure produces a clear spin polarization whose sign reverses when the chirality is flipped, and whose magnitude grows systematically with the number of dephasing electrodes, while achiral configurations exhibit no spin selectivity. The polarization remains robust even under strong Anderson disorder, showing that the engineered chiral structures provides an intrinsically stable route to spin-selective transport. These results establish a solid-state platform in the topological quantum well system for controllably generating the CISS effect.

cond-mat.mes-hall↗

arXiv2025

Anomalous Magnetoresistance beyond the Jullière Model for Spin Selectivity in Chiral Molecules

The issue of anomalous high magnetoresistance, beyond the Jullière model, observed in nonmagnetic electrode-chiral molecular-ferromagnetic electrode devices has puzzled the community for a long time. Here, by considering the magnetic proximity effect which shifts the nonmagnetic-ferromagnetic interface toward chiral molecules, we show the anomalous high magnetoresistance beyond the spin polarization in ferromagnetic electrodes even in the very weak spin-orbit coupling. Our results are in excellent agreement with the experiments, demonstrating that the spin-orbit coupling plays a fundamental role in chiral-induced spin selectivity and the magnetic proximity effect can dramatically enhance the magnetoresistance. These results elucidate the interaction between chiral molecules and ferromagnetic electrodes and facilitate the design of chiral-based spintronic devices.

physics.chem-ph↗

arXiv2025

Dynamical simulation of chiral induced spin-polarization and magnetization

Despite generally lacking ferromagnetic properties or strong spin-orbit coupling, electrons in chiral molecules exhibit unique spin-dependent transport behavior, known as chiral-induced spin selectivity (CISS). This phenomenon implies a profound connection between chirality and spin, and draws attention to the link between chirality and magnetism. Experiments in recent years have shown that chirality can induce spin-polarizations and magnetizations, providing fresh insights into interpreting chirality-related biochemical processes and designing nano-magnetic devices. In this paper, we present a dynamical theoretical model aimed at elucidating how charge-polarization combined with the CISS leads to spin-polarization and magnetization. Our theoretical model successfully explains the spin-polarization and magnetization observed in three types of experiments, where the charge-polarization is induced in the chiral molecules by the dispersion interaction, gate voltage, and molecular adsorption. The model simulates a clear time evolution process and provides a comprehensive theoretical framework for this field.

physics.chem-ph↗

arXiv2025

Spin-to-charge conversion modulated by chiral molecules

Molecular chirality and electron spin are intricately intertwined via the fascinating phenomenon of chiral-induced spin selectivity (CISS), which has garnered considerable attention due to its extensive potential applications. A recent experiment has revealed that chiral molecules self-assembled on the gold surface can modulate the inverse spin Hall effect, providing an alternative platform for studying the interplay between chirality and spin transport. Our study uncovers that this modulation stems from the CISS effect, which enhances spin currents of one spin orientation while suppressing those of the opposite spin orientation. We provide numerical results that are highly consistent with the experimental phenomena and further investigate the influence of various factors on this modulation. This work offers a theoretical explanation of previously unexplained experimental findings, and the underlying physical mechanism broadens current perspectives on understanding and applying CISS.

physics.chem-ph↗

arXiv2025

Dynamical theory of chiral-induced spin selectivity in electron donor-chiral molecule-acceptor systems

The chiral-induced spin selectivity (CISS) effect, a phenomenon where the chirality of molecules imparts significant spin selectivity to electron transfer processes, has garnered increasing interest among the chemistry, biology, and physics communities. Although this effect was discovered more than a decade ago, the dynamical process of how electron spin polarization is caused by chiral molecules is still unclear. Here, we propose a dynamical theory of electron transfer in donor-chiral molecule bridge-acceptor systems without electrodes or substrates based on the Lindblad-type master equation. We demonstrate that the molecular spin-orbit coupling generates unequal spin velocities and achieves steady spin polarization with the help of dephasing. Our work elucidates the dynamical process of CISS and may promote the applications of chiral-based spintronic devices.

physics.chem-ph↗