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Yonatan Dubi

Publications and source records attributed to Yonatan Dubi.

At least 19 recordsLinked to original sources
arXiv2026

Spinterface-like mechanism of the chirality-induced spin selectivity in donor chiral-bridge acceptor complexes

The chirality-induced spin selectivity (CISS) effect has been invoked to explain recent reports of differences in the time-resolved EPR signals between chiral and achiral molecules. However, the microscopic origin of these differences and their connection to CISS remains contested, particularly since these systems lack a metal interface. Here we introduce an intramolecular spinterface-like mechanism that naturally arises within donor-chiral bridge-acceptor (D--$\chi$B--A) complexes and quantitatively reproduces experimentally reported observed spin polarization in time-resolved EPR studies. In our two-electron Lindblad model, the photoexcited charge-transfer electron traversing the chiral bridge exchanges with the residual donor electron, which acts as a localized magnetic moment analogous to an induced magnetic moment on an electrode surface. The resulting through-bridge charge current produces an effective solenoidal field at the donor--bridge interface, breaking spin degeneracy and directional symmetry, thus enabling spin-selective transport without invoking intrinsic spin-orbit coupling on the bridge. We show that the interplay between this current-induced field, donor thermalization (which breaks time-reversal symmetry), and bridge spin mixing yields tens-of-percent polarization over realistic experimental conditions and charge-transfer time scales, matching reported CISS signatures in triads and DNA hairpins. By explicitly resolving the dependence on solenoidal coupling strength, temperature, and spin-mixing rates, the model identifies the regime in which internal spinterfaces can generate robust CISS-like spin filtering. These findings demonstrate that CISS-like signals in isolated D--$\chi$B--A complexes are fully compatible with a spinterface mechanism, providing a unified conceptual framework for interpreting both device-based and molecule-internal CISS platforms.

cond-mat.mes-hall↗
arXiv2026

Qlustering for Data Clustering via Network-Based Quantum Transport

Analog quantum computation offers a route to machine learning using controllable physical dynamics as a computational resource. However, many existing approaches rely on task-specific protocols or observables that are difficult to access experimentally, limiting generality and implementation. Here we introduce Qlustering, an unsupervised clustering framework based on steady-state quantum transport in quantum networks governed by the GKSL master equation, developed through algorithm-hardware co-design. Data are encoded as input states, and cluster assignments are inferred from steady-state output currents, avoiding full state tomography in favor of accessible transport observables. The method realizes a hybrid classical-quantum workflow in which data preparation and training are performed classically, while clustering is carried out by transport dynamics. We benchmark the method on synthetic datasets, localization, and QM9 and Iris, finding competitive performance and stability over a broad range of dephasing strengths. These results show that unlabeled data structure can be extracted directly from steady-state transport observables, identifying terminal-current readout as a native, tomography-free mechanism for unsupervised learning in open quantum networks.

quant-ph↗
arXiv2025

Qlustering: Harnessing Network-Based Quantum Transport for Data Clustering

We introduce Qlustering, a quantum-inspired algorithm for unsupervised learning that leverages network-based quantum transport to perform data clustering. In contrast to traditional distance-based methods, Qlustering treats the steady-state dynamics of quantum particles propagating through a network as a computational resource. Data are encoded as input states in a tight-binding Hamiltonian framework governed by the Lindblad master equation, and cluster assignments emerge from steady-state output currents at terminal nodes. The algorithm iteratively optimizes the network's Hamiltonian to minimize a physically motivated cost function, achieving convergence through stochastic updates. We benchmark Qlustering on synthetic datasets, a localization problem, and real-world chemical and biological data, namely subsets of the QM9 molecular database and the Iris dataset. Across these diverse tasks, Qlustering demonstrates competitive or superior performance compared with classical methods such as k-means, particularly for non-convex or high-dimensional data. Its intrinsic robustness, low computational complexity, and compatibility with photonic implementations suggest a promising route toward physically realizable, quantum-native clustering architectures.

quant-ph↗
arXiv2025

The spinterface mechanism for the chiral-induced spin selectivity effect: A Critical Perspective

The chiral-induced spin selectivity (CISS) effect, whereby chiral molecules preferentially transmit electrons of one spin orientation, remains one of the most intriguing and debated phenomena at the interface of spintronics, molecular electronics, and quantum materials. Despite extensive experimental observations across diverse platforms - including transport junctions, photoemission, and enantioselective chemistry - a comprehensive theoretical framework is still lacking. In this perspective, we critically examine the spinterface mechanism as a unifying explanation for the CISS effect. The spinterface model, which hypothesizes a feedback interaction between electron motion in chiral molecules and fluctuating surface magnetic moments, is shown to quantitatively reproduce experimental data across various systems and conditions. We contrast it with some existing theoretical models, highlighting key experimental features. Importantly, we also address open questions and criticisms of this model, including the nature of surface magnetism, the role of dissipation, and the applicability of the mechanism to non-helical or electrode-free systems. By offering falsifiable predictions and reconciling theory with experimental raw data, this work aims to sharpen the dialogue surrounding the microscopic origin of CISS and stimulate further experimental and theoretical progress.

cond-mat.mes-hall↗
arXiv2024

Surface magnetic stabilization and the photo-emission chiral-induced spin-selectivity effect

The spinterface mechanism was suggested as a possible origin for the chirality induced spin-selectivity (CISS) effect, and was used to explain and reproduce, with remarkable accuracy, experimental data from transport experiments showing the CISS effect. Here, we apply the spinterface mechanism to explain the appearance of magnetization at the interface between non-magnetic metals and chiral molecules, through the stabilization of other-wise fluctuating magnetic moments. We show that the stabilization of surface magnetic moments occurs for a wide range of realistic parameters and is robust against dephasing. Importantly, we show that the direction of the surface magnetic moments is determined by the chiral axis of the chiral molecules. Armed with the concept of stable surface magnetic moments, we then formulated a theory for the photoemission CISS effect. The theory, based on spin-dependent scattering, leads to direct predictions regarding the relation between the photoemission CISS effect, the chiral axis direction, the spinterface "size", and the tilt angle of the detector with respect to the surface. These predictions are within reach of current experimental capabilities, and may shed new light on the origin of the CISS effect.

cond-mat.mes-hall↗
arXiv2024

Time Crystals from single-molecule magnet arrays

Time crystals, a unique non-equilibrium quantum phenomenon with promising applications in current quantum technologies, mark a significant advance in quantum mechanics. Although traditionally studied in atom-cavity and optical lattice systems, pursuing alternative nanoscale platforms for time crystals is crucial. Here we theoretically predict discrete time-crystals in a periodically driven molecular magnet array, modeled by a spin-S Heisenberg Hamiltonian with significant quadratic anisotropy, taken with realistic and experimentally relevant physical parameters. Surprisingly, we find that the time-crystal response frequency correlates with the energy levels of the individual magnets and is essentially independent of the exchange coupling. The latter is unexpectedly manifested through a pulse-like oscillation in the magnetization envelope, signaling a many-body response. These results show that molecular magnets can be a rich platform for studying time-crystalline behavior and possibly other out-of-equilibrium quantum many-body dynamics.

quant-ph↗
arXiv2024

Thermodynamics of photoelectric devices

We study the nonequilibrium steady state thermodynamics of a photodevice which can operate as a solar cell or a photoconductor, depending on the degree of asymmetry of the junction. The thermodynamic efficiency is captured by a single coefficient of performance. Using a minimal model based on a two-level system, we show that when the Coulomb interaction energy matches the transport gap of the junction, the photoconductor displays maximal response, performance, and signal-to-noise ratio, while the same regime is always detrimental for the solar cell. Nevertheless, we find that the Coulomb interaction is beneficial for the solar cell performance if it lies below the transport gap. Our work sheds important light on design principles for thermodynamically efficient photodevices in the presence of Coulomb interactions.

quant-ph↗
arXiv2023

Quantum transport on networks for supervised classification

Classification, the computational process of categorizing an input into pre-existing classes, is now a cornerstone in modern computation in the era of machine learning. Here we propose a new type of quantum classifier, based on quantum transport of particles in a trained quantum network. The classifier is based on sending a quantum particle into a network and measuring the particle's exit point, which serves as a "class" and can be determined by changing the network parameters. Using this scheme, we demonstrate three examples of classification; in the first, wave functions are classified according to their overlap with predetermined (random) groups. In the second, we classify wave-functions according to their level of localization. Both examples use small training sets and achieve over 90\% precision and recall. The third classification scheme is a "real-world problem", concerning classification of catalytic aromatic-aldehyde substrates according to their reactivity. Using experimental data, the quantum classifier reaches an average 86\% classification accuracy. We show that the quantum classifier outperforms its classical counterpart for these examples, thus demonstrating quantum advantage, especially in the regime of "small data". These results pave the way for a novel classification scheme, which can be implemented as an algorithm, and potentially realized experimentally on quantum hardware such as photonic networks.

quant-ph↗
arXiv2023

Temperature-dependence of the chirality-induced spin selectivity effect -- experiments and theory

The temperature dependence of the chirality-induced spin selectivity (CISS) effect can be used to discriminate between different theoretical proposals for the mechanism of the CISS effect. Here we briefly review key experimental results and discuss the effect of temperature in different models for the CISS effect. We then focus on the recently suggested spinterface mechanism and describe the different possible effects temperature can have within this model. Finally, we analyze in detail recent experimental results from Qian, et.al., (Nature, 606, 902-908 (2022)) and demonstrate that, opposite to the original interpretation by the authors, these data indicate that the CISS effect increases with decreasing temperature. Finally, we show how the spinterface model can accurately reproduce these experimental results.

cond-mat.mes-hall↗
arXiv2022

Signatures of discrete time-crystallinity in transport through an open Fermionic chain

Discrete time-crystals are periodically driven quantum many-body systems with broken discrete-time translational symmetry, a non-equilibrium steady state representing self-organization of motion of quantum particles. Observations of discrete time-crystalline order are currently limited to magneto-optical experiments. Crucially, it was never observed in a transport experiment performed on systems connected to external electrodes. Here we demonstrate that both discrete time-crystal and quasi-crystal survive a very general class of environment corresponding to single-particle gain and loss through system-electrode coupling over experimentally relevant timescales. Using dynamical symmetries, we analytically identify the conditions for observing time-crystalline behavior in a periodically driven open Fermi-Hubbard chain attached to electrodes. Remarkably, the spin-polarized transport current directly manifests the existence of a time-crystalline behavior. Our findings are verifiable in present-day experiments with quantum-dot arrays and Fermionic ultra-cold atoms in optical lattices.

cond-mat.mes-hall↗
arXiv2022

Emergence and Dynamical Stability of Charge Time-Crystal in a Current-Carrying Quantum Dot Simulator

Periodically-driven open quantum systems that never thermalize exhibit a discrete time-crystal behavior, a non-equilibrium quantum phenomenon that has shown promise in quantum information processing applications. Measurements of time-crystallinity are currently limited to (magneto-) optical experiments in atom-cavity systems and spin-systems making it an indirect measurement. We theoretically show that time-crystallinity can be measured directly in the charge-current from a spin-less Hubbard ladder, which can be simulated on a quantum-dot array. We demonstrate that one can dynamically tune the system out and then back into the time-crystal phase, proving its robustness against external forcings. These findings motivate further theoretical and experimental efforts to simulate the time-crystal phenomena in current-carrying nano-scale systems.

cond-mat.mes-hall↗
arXiv2022

Theory of Non-equilibrium "Hot" Carriers in Direct Band-gap Semiconductors Under Continuous Illumination

The interplay between the illuminated excitation of carriers and subsequent thermalization and recombination leads to the formation of non-equilibrium distributions for the "hot" carriers and to heating of both electrons, holes and phonons. In spite of the fundamental and practical importance of these processes, there is no theoretical framework which encompasses all of them and provides a clear prediction for the non-equilibrium carrier distributions. Here, a self-consistent theory accounting for the interplay between excitation, thermalization, and recombination in continuously-illuminated semiconductors is presented, enabling the calculation of non-equilibrium carrier distributions. We show that counter-intuitively, distributions deviate more from equilibrium under weak illumination than at high intensities. We mimic two experimental procedures to extract the carrier temperatures and show that they yield different dependence on illumination. Finally, we provide an accurate way to evaluate photoluminescence efficiency, which, unlike conventional models, predicts correctly the experimental results. These results provide a starting point towards examining how non-equilibrium features will affect properties hot-carrier based application.

physics.optics↗
arXiv2022

The photothermal nonlinearity in plasmon-assisted photocatalysis

Understanding the intricate relation between illumination and temperature in metallic nano-particles is crucial for elucidating the role of illumination in various physical processes which rely on plasmonic enhancement but are also sensitive to temperature. Recent studies have shown that the temperature rise in optically-thick ensembles of metal nanoparticles under intense illumination is dominated by the thermal conductivity of the host, rather than by the optical properties of the metal or the host. Here, we show that the temperature dependence of the thermal conductivity of the host dominates the nonlinear photothermal response of these systems. In particular, this dependence typically causes the temperature rise to become strongly sublinear, reaching even several tens of percent. We then show that this can explain experimental observations in several recent plasmon-assisted photocatalysis experiments. This shows that any claim for dominance of non-thermal electrons in plasmon-assisted photocatalysis must account first for this photothermal nonlinear mechanism.

physics.chem-ph↗
arXiv2022

Distinguishing thermal from non-thermal ("hot") carries in illuminated molecular junctions

The search for the signature of non-thermal (so-called ``hot'') electrons in illuminated plasmonic nanostructures requires a detailed understanding of the non-equilibrium electron distribution under illumination, as well as a careful design of the experimental system employed to distinguish non-thermal electrons from thermal ones. Here, we provide a theory for using plasmonic molecular junctions to achieve this goal. We show how non-thermal electrons can be measured directly and separately from the unavoidable thermal response, and discuss the relevance of our theory to recent experiments.

cond-mat.mes-hall↗
arXiv2021

Matters Arising in -- "Plasmon-driven carbon-fluorine (C(sp^$3$)-F) bond activation with mechanistic insights into hot-carrier-mediated pathways"

In a recent paper~[Nature Catalysis 3, 573 (2020)], Robatjazi {\em et al.} demonstrate hydrodefluorination on Al nanocrystals decorated by Pd islands under illumination and under external heating. They conclude that photocatalysis accomplishes the desired transformation \ce{CH3F + D2 -> CH3D + DF} efficiently and selectively due to "hot" electrons, as evidenced by an illumination-induced reduction of the activation energy. Although some of the problems identified in prior work by the same group have been addressed, scrutiny of the data in~[Nature Catalysis 3, 573 (2020)] raises doubts about both the methodology and the central conclusions. First, we show that the thermal control experiments in~[Nature Catalysis 3, 573 (2020)] do not separate thermal from "hot electron" contributions, and therefore any conclusions drawn from these experiments are invalid. We then show that an improved thermal control implies that the activation energy of the reaction does not change, and that an independent purely thermal calculation (based solely on the sample parameters provided in the original manuscript) explains the measured data perfectly. For the sake of completeness, we also address technical problems in the calibration of the thermal camera, an unjustifiable disqualification of some of the measured data, as well as concerning aspects of the rest of the main results, including the mass spectrometry approach used to investigate the selectivity of the reaction, and claims about the stoichiometry and reaction order. All this shows that the burden of proof for involvement of hot electrons has not been met.

physics.chem-ph↗
arXiv2021

Do photosynthetic complexes use quantum coherence to increase their efficiency? Probably not

Answering the titular question has become a central motivation in the field of quantum biology, ever since the idea was raised following a series of experiments demonstrating wave-like behavior in photosynthetic complexes. Here, we report a direct evaluation of the effect of quantum coherence on the efficiency of three natural complexes. An open quantum systems approach allows us to simultaneously identify their level of "quantumness" and efficiency, under natural physiological conditions. We show that these systems reside in a mixed quantum-classical regime, characterized by dephasing-assisted transport. Yet, we find that the change in efficiency at this regime is minute at best, implying that the presence of quantum coherence does not play a significant role in enhancing efficiency. However, in this regime efficiency is independent of any structural parameters, suggesting that evolution may have driven natural complexes to their parameter regime in order to "design" their structure for other uses.

physics.bio-ph↗
arXiv2020

Recent developments in plasmon-assisted photocatalysis -- a personal perspective

It has been known for many years that metallic nanoparticles can catalyse various chemical reactions, both in the dark and under illumination, through different mechanisms. In the last decade or so, many claims of plasmon-assisted "hot" electron driven catalysis of bond-dissociation reactions have been put forward. These claims were \XYZ{challenged} in a recent series of papers, where both the underlying theory of "hot" electron generation and the use of specific experimental setups to discover them in chemical reactions were examined in detail. The conclusion that arose from these works is that as long as temperature gradients exist inside the system (as for typical experimental setups) a quantification of non-thermal effects is close to impossible. Instead, a standard thermal theory was shown to be capable of explaining the experimental findings quite accurately. Here, we review the central lines of thought that led to these conclusions, from a personal perspective. We lay out the key aspects of the theory, and point to the specific caveats one must be aware of in performing photo-catalysis experiments. Finally, we provide some future directions of study.

physics.optics↗