Realization of quantum nanomagnets in metal-free porphyrins

Abstract Quantum nanomagnets exhibit collective quantum behaviors beyond the usual long range ordered states due to the interplay of low dimension, competing interactions and strong quantum fluctuations. Despite numerous theoretical works treating quantum magnetism, the experimental study of individual quantum nanomagnets remains very challenge, greatly hindering the development of this cutting-edge field. Here, we demonstrate an effective strategy to realize individual quantum nanomagnets in metal-free porphyrins by using combined on-surface synthesis and atom manipulation approaches, with the ultimate ability to arrange coupled spins one by one as envisioned by Richard Feynman 60 years ago. A series of metal-free porphyrin nanomagnets have been constructed on Au(111) and their collective magnetic properties have been thoroughly characterized on the atomic scale by scanning probe microscopy together with theoretical calculations. Our results reveal that the constructed S=1/2 antiferromagnets host a gapped excitation in consistent with isotropic Heisenberg antiferromagnets S=1/2 model, while the S=1 antiferromagnets with odd-number units exhibit two zero-mode end states due to quantum fluctuations. Our achieved strategy not only provides a unique testing bed to study the strongly correlated effects of quantum magnetism in purely organic materials, but expands the functionalities of porphyrins with implications for quantum technological applications.

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Functional-integral approach to strongly correlated Fermi systems: Quantum fluctuations beyond the Gutzwiller approximation

Physical Review B ◽

10.1103/physrevb.41.142 ◽

1990 ◽

Vol 41 (1) ◽

pp. 142-148 ◽

Cited By ~ 102

Author(s):

M. Lavagna

Keyword(s):

Quantum Fluctuations ◽

Functional Integral ◽

Integral Approach ◽

Strongly Correlated ◽

Fermi Systems ◽

Gutzwiller Approximation

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Application of Atom Manipulation for Fabricating Nanoscale and Atomic-Scale Structures on Si Surfaces

Advances in Scanning Probe Microscopy - Advances in Materials Research ◽

10.1007/978-3-642-56949-4_4 ◽

2000 ◽

pp. 91-112

Author(s):

T. Hashizume ◽

S. Heike ◽

T. Hitosugi ◽

K. Kitazawa

Keyword(s):

Atomic Scale ◽

Atom Manipulation ◽

Scale Structures

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Strongly correlated electron systems and quantum magnetism

Condensed Matter Physics ◽

10.5488/cmp.23.40101 ◽

2020 ◽

Vol 23 (4) ◽

pp. 40101

Author(s):

Freericks ◽

Strečka

Keyword(s):

Strongly Correlated Electron Systems ◽

Quantum Magnetism ◽

Strongly Correlated ◽

Electron Systems ◽

Strongly Correlated Electron ◽

Correlated Electron Systems ◽

Correlated Electron

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[FeFe] Hydrogenase based Prototype Photosensitizer-Catalyst Dyad for Hydrogen Generation under Visible Light

10.33774/chemrxiv-2021-1wh3l-v2 ◽

2021 ◽

Author(s):

Philipp Buday ◽

Chizuru Kasahara ◽

Elisabeth Hofmeister ◽

Daniel Kowalczyk ◽

Michael K. Farh ◽

...

Keyword(s):

Visible Light ◽

Precious Metal ◽

Hydrogen Generation ◽

Theoretical Calculations ◽

Electrochemical Techniques ◽

Time Resolved ◽

Metal Free ◽

Pi Conjugated ◽

Visible Light Driven ◽

Light Absorbers

Inspired by the active center of the natural [FeFe] hydrogenases, we designed a compact and precious metal-free photosensitizer-catalyst dyad (PS-CAT) for photocatalytic hydrogen evolution under visible light irradiation. PS-CAT represents a prototype dyad comprising pi-conjugated oligothiophenes as light absorbers. PS-CAT and its interaction with the sacrificial donor 1,3-dimethyl-2-phenylbenzimidazoline were studied by steady-state and time-resolved spectroscopy coupled with electrochemical techniques and visible light-driven photocatalytic investigations. Operando EPR spectroscopy revealed the formation of an active [Fe(I)Fe(0)] species – in accordance with theoretical calculations – presumably driving photocatalysis effectively (TON ≈ 210).

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Orbital-Dependent Photodynamics of Strongly Correlated Clusters

10.33774/chemrxiv-2021-3c1hs ◽

2021 ◽

Author(s):

Jacob Garcia ◽

Scott Sayres

Keyword(s):

Theoretical Calculations ◽

Advanced Materials ◽

Strongly Correlated ◽

Relaxation Dynamics ◽

Pump Probe ◽

Defect Sites ◽

Atomic Precision ◽

Bulk Scale ◽

Probe Spectroscopy

Understanding the role of defect sites on the mechanism and lifetime of photoexcited state relaxation is critical for the ration-al design of advanced materials. Here, the ultrafast electronic relaxation dynamics of neutral nickel oxide clusters were inves-tigated with femtosecond pump-probe spectroscopy and supported with theoretical calculations to reveal that their excited state lifetimes are strongly dependent on the nature of the electronic transition. Absorption of a UV photon produces short lived (lifetime ~110 fs) dynamics in stoichiometric (NiO)n clusters (n < 6) that are attributed to a ligand to metal charge transfer (LMCT) and produces metallic-like electron-electron scattering. Oxygen vacancies introduce excitations with Ni-3d→Ni-4s and 3d→4p character, which increases the lifetimes of the sub-picosecond response by up to 80% and enables the formation of long-lived (lifetimes > 2.5 ps) states. The atomic precision and tunability of gas phase clusters are employed to highlight a unique reliance on the Ni orbital contributions to the photoexcited lifetimes, providing new insights to the anal-ogous band edge excitation dynamics of strongly correlated bulk-scale NiO materials.

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Atomic-scale interface engineering of Majorana edge modes in a 2D magnet-superconductor hybrid system

Science Advances ◽

10.1126/sciadv.aav6600 ◽

2019 ◽

Vol 5 (7) ◽

pp. eaav6600 ◽

Cited By ~ 33

Author(s):

Alexandra Palacio-Morales ◽

Eric Mascot ◽

Sagen Cocklin ◽

Howon Kim ◽

Stephan Rachel ◽

...

Keyword(s):

Hybrid System ◽

Theoretical Calculations ◽

Real Space ◽

Scanning Tunneling Spectroscopy ◽

Atomic Scale ◽

Scanning Tunneling ◽

Edge States ◽

Interface Engineering ◽

New Paradigm ◽

Topological Quantum

Topological superconductors are predicted to harbor exotic boundary states—Majorana zero-energy modes—whose non-Abelian braiding statistics present a new paradigm for the realization of topological quantum computing. Using low-temperature scanning tunneling spectroscopy, here, we report on the direct real-space visualization of chiral Majorana edge states in a monolayer topological superconductor, a prototypical magnet-superconductor hybrid system composed of nanoscale Fe islands of monoatomic height on a Re(0001)-O(2 × 1) surface. In particular, we demonstrate that interface engineering by an atomically thin oxide layer is crucial for driving the hybrid system into a topologically nontrivial state as confirmed by theoretical calculations of the topological invariant, the Chern number.

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Interactions between Ultrastable Na4Ag44(SR)30 Nanoclusters and Coordinating Solvents: Uncovering the Atomic-scale Mechanism

10.26434/chemrxiv.12407117 ◽

2020 ◽

Author(s):

Daniel M. Chevrier ◽

Brian E. Conn ◽

Bo Li ◽

De-En Jiang ◽

Terry P. Bigioni ◽

...

Keyword(s):

Theoretical Calculations ◽

Atomic Scale ◽

Water Molecules ◽

X Ray ◽

Silver Nanocluster ◽

Ligand Interactions ◽

Surface Metal ◽

Solvent Molecules ◽

Aqueous Conditions ◽

Metal Ligand

We report the mechanism on the ultrahigh stability of Na4Ag44(SR)30 by uncovering how coordinating solvents interact with the Na4Ag44(SR)30 nanocluster at the atomic scale. Through synchrotron X-ray experiments and theoretical calculations, it was found that strongly coordinating aprotic solvents interact with surface Ag atoms, particularly between ligand bundles, which compresses the Ag core and relaxes surface metal-ligand interactions. Furthermore, water was used as a cosolvent to demonstrate that semi-aqueous conditions play an important role in protecting exposed surface regions and can further influence the local structure of the silver nanocluster itself. Notably, under semi-aqueous conditions, aprotic coordinating solvent molecules preferentially remain on the metal surface while water molecules interact with ligands, and ligand bundling persisted across the varied solvation conditions.

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CxNy: New Carbon Nitride Organic Photocatalysts

Frontiers in Materials ◽

10.3389/fmats.2021.772200 ◽

2021 ◽

Vol 8 ◽

Author(s):

Nieves López-Salas ◽

Josep Albero

Keyword(s):

Carbon Nitride ◽

Theoretical Calculations ◽

Chemical Properties ◽

Electronic Configuration ◽

High Refractive Index ◽

Visible Range ◽

Metal Free ◽

Recent Success ◽

New Family ◽

Chemical Morphology

The search for metal-free and visible light-responsive materials for photocatalytic applications has attracted the interest of not only academics but also the industry in the last decades. Since graphitic carbon nitride (g-C3N4) was first reported as a metal-free photocatalyst, this has been widely investigated in different light-driven reactions. However, the high recombination rate, low electrical conductivity, and lack of photoresponse in most of the visible range have elicited the search for alternatives. In this regard, a broad family of carbon nitride (CxNy) materials was anticipated several decades ago. However, the attention of the researchers in these materials has just been awakened in the last years due to the recent success in the syntheses of some of these materials (i.e., C3N3, C2N, C3N, and C3N5, among others), together with theoretical simulations pointing at the excellent physico-chemical properties (i.e., crystalline structure and chemical morphology, electronic configuration and semiconducting nature, or high refractive index and hardness, among others) and optoelectronic applications of these materials. The performance of CxNy, beyond C3N4, has been barely evaluated in real applications, including energy conversion, storage, and adsorption technologies, and further work must be carried out, especially experimentally, in order to confirm the high expectations raised by simulations and theoretical calculations. Herein, we have summarized the scarce literature related to recent results reporting the synthetic routes, structures, and performance of these materials as photocatalysts. Moreover, the challenges and perspectives at the forefront of this field using CxNy materials are disclosed. We aim to stimulate the research of this new generation of CxNy-based photocatalysts, beyond C3N4, with improved photocatalytic efficiencies by harnessing the striking structural, electronic, and optical properties of this new family of materials.

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Magnetoelectric phase transition driven by interfacial-engineered Dzyaloshinskii-Moriya interaction

Nature Communications ◽

10.1038/s41467-021-25759-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Xin Liu ◽

Wenjie Song ◽

Mei Wu ◽

Yuben Yang ◽

Ying Yang ◽

...

Keyword(s):

Phase Transition ◽

Atomic Scale ◽

Strongly Correlated ◽

Electron Systems ◽

Correlated Electron Systems ◽

Quantum Phases ◽

Interfacial Engineering ◽

Correlated Electron ◽

Microscopic Origin ◽

Moriya Interaction

AbstractStrongly correlated oxides with a broken symmetry could exhibit various phase transitions, such as superconductivity, magnetism and ferroelectricity. Construction of superlattices using these materials is effective to design crystal symmetries at atomic scale for emergent orderings and phases. Here, antiferromagnetic Ruddlesden-Popper Sr2IrO4 and perovskite paraelectric (ferroelectric) SrTiO3 (BaTiO3) are selected to epitaxially fabricate superlattices for symmetry engineering. An emergent magnetoelectric phase transition is achieved in Sr2IrO4/SrTiO3 superlattices with artificially designed ferroelectricity, where an observable interfacial Dzyaloshinskii-Moriya interaction driven by non-equivalent interface is considered as the microscopic origin. By further increasing the polarization namely interfacial Dzyaloshinskii-Moriya interaction via replacing SrTiO3 with BaTiO3, the transition temperature can be enhanced from 46 K to 203 K, accompanying a pronounced magnetoelectric coefficient of ~495 mV/cm·Oe. This interfacial engineering of Dzyaloshinskii-Moriya interaction provides a strategy to design quantum phases and orderings in correlated electron systems.

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