BUSCADOR RECOLECTA

Spin–orbit coupling gives rise to a range of spin-charge interconversion phenomena in nonmagnetic systems where certain spatial symmetries are reduced or absent. Chirality-induced spin-selectivity (CISS), a term that generically refers to a spin-dependent electron transfer in nonmagnetic chiral systems, is one such case, appearing in a variety of seemingly unrelated situations ranging from inorganic materials to molecular devices. In particular, the origin of CISS in molecular junctions is a matter of an intense current debate. Here, we derive a set of geometrical conditions for this effect to appear, hinting at the fundamental role of symmetries beyond otherwise relevant quantitative issues. Our approach, which draws on the use of point-group symmetries within the scattering formalism for transport, shows that electrode symmetries are as important as those of the molecule when it comes to the emergence of a spin-polarization and, by extension, to the possible appearance of CISS. It turns out that standalone metallic nanocontacts can exhibit spin-polarization when relative rotations which reduce the symmetry are introduced. As a corollary, molecular junctions with achiral molecules can also exhibit spin-polarization along the direction of transport, provided that the whole junction is chiral in a specific way. This formalism also allows the prediction of qualitative changes of the spin-polarization upon substitution of a chiral molecule in the junction with its enantiomeric partner. Quantum transport calculations based on density functional theory corroborate all of our predictions and provide further quantitative insight within the single-particle framework., J.J.P. and M.A.G.B acknowledge financial support from Spanish MICIN through Grant No. PID2019-109539GB-C43/AEI/10.13039/501100011033, the María de Maeztu Program for Units of Excellence in R&D (Grant No. CEX2018-000805-M), the Comunidad Autónoma de Madrid through the Nanomag COST-CM Program (Grant No. S2018/NMT-4321), the Generalitat Valenciana through Programa Prometeo/2021/017, the Centro de Computación Científica of the Universidad Autónoma de Madrid, and the computer resources of the Red Española de Supercomputación. L.A.Z. thanks financial support from MCIN/AEI/10.13039/501100011033 (grant PID2021-125604NB-I00) and from the Universidad Autónoma de Madrid/Comunidad de Madrid (Grant No. SI3/PJI/2021-00191). C.S. thanks the financial support from the Generalitat Valenciana through CIDEXG/2022/45, CDEIGENT/2018/028 and PROMETEO/2021/017. S.P. acknowledges the grant from Erasmus+ 2018 programme (Collaboration between University of Tehran, Iran and Autonomous University of Madrid, Spain).

We study indirect exchange interactions between localized spins of magnetic impurities in spin valley coupled systems described with the Kane-Mele model. Our model captures the main ingredients of the energy bands of the 1H transition metal dichalcogenide (TMD) monolayers, such as 1H-MoS2 and 1H-NbSe2. To obtain the effective interactions, we use the exact diagonalization of the Hamiltonian, avoiding momentum cutoffs. We start by comparing the standard perturbation expansion in terms of the Kondo exchange with the exact calculation of the interaction, treating the local spins classically. We find that perturbation theory works well even beyond the regime where the relevant figure of merit, the ratio between the exchange J and the hopping t, is small. We verify that the effective indirect exchange Hamiltonian derived from perturbation theory also works in the nonperturbative regime. Additionally, we analyze the interplay between the symmetry of the different terms of the interaction (Heisenberg, Ising, and Dzyaloshinskii-Moriya), the Fermi-surface topology, and the crystallographic direction in which the impurities are placed. We show that the indirect exchange along the armchair direction is actually Heisenberg-like, due to the reflection symmetry of the crystal structure around this direction. Finally, we explore the exploitation of indirect exchange, combined with atomic manipulation, to engineer the Majumdar-Ghosh model. Our results show that TMDs provide an extremely versatile platform to engineer indirect exchange interactions., This study forms part of the Advanced Materials programme and was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana (MFA/2022/045). We acknowledge Programa Operativo FEDER/Junta de Andalucía—Consejería de Transformación Económica, Industria, Conocimiento, y Universidades (Grant No. P18-FR-4834). The Albaicín supercomputer of the University of Granada is also acknowledged for providing computational time and facilities. B.B. acknowledges financial support from AEI under Project No. PID2021-125604NB-I00. J.F.R. acknowledges financial support from FCT (Grant No. PTDC/FIS-MAC/2045/2021), SNF Sinergia (Grant Pimag), Generalitat Valenciana funding Prometeo 2021/017 and MFA/2022/045, and funding from MICIIN-Spain (Grant No. PID2019-109539GB-C41).

Ultraviolet (UV) processing in the interstellar medium (ISM) induces the dehydrogenation of hydrocarbons. Aliphatics, including alkanes, are present in different interstellar environments, being prevalently formed in evolved stars; thus, the dehydrogenation by UV photoprocessing of alkanes plays an important role in the chemistry of the ISM, leading to the formation of unsaturated hydrocarbons and eventually to aromatics, the latter ubiquitously detected in the ISM. Here, through combined experimental results and ab initio calculations, we show that UV absorption (mainly at the Lyα emission line of hydrogen at 121.6 nm) promotes an alkane to an excited Rydberg state from where it evolves toward fragmentation, inducing the formation of olefinic C=C bonds, which are necessary precursors of aromatic hydrocarbons. We show that the photochemistry of aliphatics in the ISM does not primarily produce direct hydrogen elimination but preferential C–C photocleavage. Our results provide an efficient synthetic route for the formation of unsaturated aliphatics, including propene and dienes, and suggest that aromatics could be formed in dark clouds by a bottom-up mechanism involving molecular fragments produced by UV photoprocessing of aliphatics., G.T.-C. acknowledges funding from the Comunidad Autónoma de Madrid (grant No. PEJ-2021-AI/IND-21143). J.I.M.-M. acknowledges grant No. PID2021-125604NB-I00 MCIN/AEI/10.13039/501100011033 by the "European Union NextGenerationEU/PRTR." G.S. acknowledges grant No. RYC2020-029810-I funded by MCIN/AEI/10.13039/501100011033 and by "ESF Investing in your future." This work has been partially funded by grant No. PID2020-113142RB-C21 funded by MCIN/AEI/10.13039/501100011033 and grant No. PLEC2021-007906 funded by MCIN/AEI/10.13039/501100011033 by the "European Union NextGenerationEU/PRTR." Partial funding by FotoArt-CM (P2018/NMT 4367) and Photosurf-CM (Y2020/NMT-6469) projects funded by Comunidad Autónoma de Madrid and cofinanced by European Structural Funds is also acknowledged., Peer reviewed

Continuous research on new chiral molecular materials brings new exciting properties to the field of molecular electronics. The discovery of the chirality-induced spin selectivity (CISS) effect has expanded the list of applications for chiral structures, opening promising avenues for their exploitation in molecular spintronics. In this work, the persistent propeller-like organic perchlorotriphenylmethyl (PTM) radical is investigated as a potential spin filter combining chirality and paramagnetism. In particular, two different PTM derivatives, mono- and bis-functionalized, with one or two terminal alkyne groups have been used for the preparation of enantioenriched solid-state assemblies. The analysis of their chiroptical properties reveals that the functionalization does not play a crucial role in their final conformational stability and highlights the dissimilarities of the racemization barriers in solution and solid states. Spin-dependent electrochemical and charge transport measurements of enantioenriched PTM-based self-assembled monolayers did not reveal the existence of the CISS effect. Density functional theory quantum transport calculations show that the most dominant contribution to the spin polarization would not be CISS-related polarization, but the one intrinsically associated with the radical spin. Nevertheless, at room temperature this contribution is affected by thermal fluctuations averaging to a net zero spin polarization., The work was supported by Generalitat de Catalunya (2021SGR00443), PID2019-111682RB-I00, PID2022-141393OB-I0, PID2021-127521NB-I00, PID2021-125604NB-I00, PID2019- 109539GB-C43, and PID2022-141712NB-C21 funded by MCIN/AEI/10.13039/501100011033 and ERDF “A way of making Europe” and TED2021-131323B-I00 NextGenerationEU, the “Severo Ochoa” Programme for Centers of Excellence in R&D FUNFUTURE CEX2019-000917-S through the competitive FUNMAT-FIP-2018 grant and the European Commission – NextGenerationEU (Regulation EU 2020/2094), through CSIC's Quantum Technologies Platform (QTEP). J. C.-T. thanks the DOC-FAM fellowship, grant agreement No. 754397 (H2020-MSCA-COFUND-2016). J. C.-T. is enrolled at the UAB Materials Science PhD program. S. M-L. acknowledges the funding received from the Spanish Junta de Andalucía (DOC 01165). The authors thank the Centro de Servicios de Informática y Redes de Comunicación (CSIRC), UGR, for providing the computing time. L. A. Z. and J. J. P. acknowledge María de Maeztu Program for Units of Excellence in R&D (Grant No. CEX2018-000805-M), Generalitat Valenciana through Programa Prometeo (2021/017) and Centro de Computación Científica of the Universidad Autónoma de Madrid., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S)., Peer reviewed

<ul>Data employed to obtain the results contained in the manuscript "Antiaromatic non-alternant heterocyclic compounds as molecular wires".</ul>

<ul>The methodology applied is a combination of DFT and Green´s functon techniques. </ul>

We report an experimental and theoretical study of the electron-phonon coupling for alpha-Sn/Ge(111), a prototypical triangular lattice surface, closely related to Sn/Si(111)-( √3 x √3), where recent experimental evidence has found superconductivity [X. Wu et al., Phys. Rev. Lett. 125, 117001 (2020)]. We concentrate our study on the (3 x 3) phase of alpha-Sn/Ge(111) that appears between 150 and 120 K and has a well-known geometry with a half-filled electronic band around the Fermi energy. We show that this surface presents a giant electron-phonon interaction that can be considered at least partially responsible for the different phases that this system shows at very low temperature. Our theoretical results indicate that indeed the electron-phonon interaction in alpha-Sn/Ge(111)-(3 x 3) is unusually large, since we find that lambda, the electron mass enhancement for the half-filled band, is lambda = 1.3. This result is in good agreement with the experimental value obtained from high-resolution angle-resolved photoemission spectroscopy measurements, which yield lambda = 1.45 +/- 0.1

Continuous research on new chiral molecular materials brings new exciting properties to the field of molecular electronics. The discovery of the chirality-induced spin selectivity (CISS) effect has expanded the list of applications for chiral structures, opening promising avenues for their exploitation in molecular spintronics. In this work, the persistent propeller-like organic perchlorotriphenylmethyl (PTM) radical is investigated as a potential spin filter combining chirality and paramagnetism. In particular, two different PTM derivatives, mono- and bis-functionalized, with one or two terminal alkyne groups have been used for the preparation of enantioenriched solid-state assemblies. The analysis of their chiroptical properties reveals that the functionalization does not play a crucial role in their final conformational stability and highlights the dissimilarities of the racemization barriers in solution and solid states. Spin-dependent electrochemical and charge transport measurements of enantioenriched PTM-based self-assembled monolayers did not reveal the existence of the CISS effect. Density functional theory quantum transport calculations show that the most dominant contribution to the spin polarization would not be CISS-related polarization, but the one intrinsically associated with the radical spin. Nevertheless, at room temperature this contribution is affected by thermal fluctuations averaging to a net zero spin polarization.