arXiv subjects

Yi-Jun Wang

Publications and source records attributed to Yi-Jun Wang.

4 recordsLinked to original sources

arXiv2026

Strongly entangled Quantum Spin Rings driven by H\"uckel rule

Quantum spin rings represent an intriguing platform for studying unconventional magnetic order and exotic quantum phases, and they are also promising materials for emerging quantum technologies. Conventional spin systems consist of a set of weakly interacting localized spins that are well described by the Heisenberg spin models. Here, we demonstrate that strong interactions between radical centers in macrocycles of different sizes lead to fluctuations in the total number of unpaired electrons and to non-trivial antiferromagnetic order that extends beyond the Heisenberg picture. We demonstrate that the electronic structure of these spin rings is governed by the concept of 4n/4n+2 H\"uckel (anti)aromaticity for even-membered rings, whereas odd-membered rings possess a highly degenerate frustrated magnetic ground state. The strongly coupled spin rings are experimentally realized through the on-surface synthesis of {\pi}-magnetic carbon-based macrocycles, which consist of [2]triangulene units. The close correlation between the electronic structure and the H\"uckel aromaticity rule is revealed by scanning tunneling spectroscopy and multireference calculations. This work establishes a novel design principle employing the concept of H\"uckel aromaticity for quantum spin macrocycles.

cond-mat.mes-hall↗

arXiv2026

Quantum Spin-1/2 Rings Built from [2]Triangulene Molecular Units

Quantum spin rings represent fundamental model systems that exhibit distinctive quantum phenomena-such as quantum critical behavior and quasiparticle excitations-arising from their periodic boundary conditions and enhanced quantum fluctuations. Here, we report the on-surface synthesis and atomic-scale characterization of antiferromagnetic S=1/2 quantum spin rings composed of pristine and unmodified [2]triangulene units on a Au(111) surface. Using stepwise on-surface synthesis followed by STM tip-induced dehydrogenation, we precisely constructed cyclic five- and six-membered spin rings and investigated their spin states via scanning probe microscopy and multireference calculations. Nc-AFM imaging reveals that the six-membered ring retains a planar geometry, whereas the five-membered ring exhibits pronounced structural distortion. The six-membered ring hosts a uniform excitation gap that can be accurately described by a Heisenberg spin model and multireference CASCI calculations. In contrast, the distorted five-membered ring displays spin ground states with asymmetric spatial distributions due to degeneracy lifting induced by structural distortion. Our findings establish a versatile molecular platform for exploring correlated magnetism and quantum spin phenomena in cyclic organic magnetic architectures with disorder.

cond-mat.mtrl-sci↗

arXiv2025

Experimental investigation of a novel liquid metal plasma facing component with pre-filled microstructures

Regarding the plasma facing components (PFCs) in nuclear fusion, liquid metal PFCs with stable free surface flow on PFC surface are considered a promising alternative. However, due to the poor wettability of liquid metal on most solid substrates and the complex magnetohydrodynamic (MHD), the realization of stable free surface flow on PFCs surface is challenging. In the present study, using the 3D printed methods, we developed a novel liquid metal PFC surface with MIcrostructures pre-FIlled by Liquid Metal (MIFILM) to realize a stable free liquid metal surface flow. The experimental results demonstrated that due to the existence of MIFILM, the apparent contact angle (ACA) of liquid metal changes from 140$^{\circ}$ to approximately 20$^{\circ}$, indicating a transition from hydrophobic to hydrophilic. When the liquid metal flows on the MIFILM substrate, it is found that the liquid metal can completely spread on the surface with a stable and orderly free surface, even at a low flow rate. Moreover, the liquid metal could exhibit sustained spreading properties on the MIFILM substrate under a strong transverse magnetic field (up to 1.6 T). Results indicate that the magnetic field induces limited MHD drag but also accelerates the flow via two-dimensional effects. When the Stuart number $N<1$, the flow accelerates and the film thickness decreases. For $N>1$, both flow velocity and film thickness gradually stabilize. Therefore, the present novel MIFILM can offer a good choice for liquid metal PFC substrates in nuclear fusion.

physics.flu-dyn↗

arXiv2025

Engineering Graphene Nanoribbons via Periodically Embedding Oxygen Atoms

Heteroatom doping is an important method for engineering graphene nanoribbons (GNRs) because of its ability to modify electronic properties by introducing extra electrons or vacancies. However, precisely integrating oxygen atoms into the lattice of GNRs is unexplored, and the resulting electronic properties remain elusive. Here, we achieve the precise embedding of oxygen atoms into the lattice of GNRs via in situ formation of pyrans, synthesizing two types of oxygen-doped GNRs (O-doped chevron-GNR and O-doped chiral (2,1)-GNR). Using scanning tunneling microscopy, non-contact atomic force microscopy, and density functional theory calculations, the atomic structures and electronic properties of O-doped GNRs are determined, demonstrating that both GNRs are direct bandgap semiconductors with different sensitivities to oxygen dopants. Oxygen dopants have a minor impact on the bandgap of chevron-GNR but a significant effect on the bandgap of chiral (2,1)-GNR, which is attributed to the difference in density of states near the Fermi level between substituted intrinsic carbon atoms and their pristine counterparts. Compared with the pristine chiral (2,1)-GNR, the band structure of O-doped chiral (2,1)-GNR exhibits unexpected band edges transition, which is ascribed to sp2-hybridized oxygen atoms which introduces additional electrons to the conduction band of chiral (2,1)-GNR, leading to the upward shift of Fermi surface.

cond-mat.mtrl-sci↗