arXiv subjects

Hongyan Chen

Publications and source records attributed to Hongyan Chen.

4 recordsLinked to original sources

arXiv2026

Observation of the Ferromagnetic Kondo Effect

The quest for quantum ground states beyond the conventional Fermi-liquid paradigm remains a central challenge in many-body physics. The ferromagnetic Kondo effect represents a particularly intriguing case: an exotic variant of the Kondo effect in which an asymptotically free spin gives rise to singular Fermi-liquid behavior. Despite its theoretical importance, this regime has long eluded experimental observation owing to its subtle spectroscopic signatures, vanishingly small energy scales, and strict symmetry constraints in conventional nanostructures. Here, we demonstrate the coexistence of the ferromagnetic and overscreened Kondo effects within a single molecular spin system$\unicode{x2014}$a triangulene dimer comprising spin-1 and spin-1/2 units adsorbed on a metal surface. Low-temperature scanning tunneling spectroscopy reveals characteristic signatures of singular Fermi-liquid behavior, which are fully supported by many-body calculations. The unique molecular design provides intrinsic control over spin configuration and coupling asymmetry, allowing distinct many-body regimes to be accessed within the same platform. Our results establish a robust strategy for realizing non-Fermi-liquid physics at the atomic scale and demonstrate that ferromagnetic Kondo behavior can not only be observed but also deliberately engineered in molecular systems.

cond-mat.mes-hall↗

arXiv2026

Fast Nuclear Spin Read-Out in Single Molecule Magnets

Nuclear spins in 4f single-molecule magnets (SMMs) are promising qubits or qudits candidates for quantum information processing due to their relative isolation and reduced susceptibility to environmental disturbances, while their hyperfine coupling to the 4f magnetic moments enable readout and control. So far, the nuclear spin states of individual TbPc2 SMMs have been detected in transport measurements via the spin-cascade effect. Here, we demonstrate a fast, field-sweep-free readout of nuclear spin in individual 163DyPc2 (I = 5/2) and 159TbPc2 (I = 3/2) using millikelvin spin-polarized scanning tunneling microscopy. This fast readout is enabled by the hyperfine interactions, which modifies the statistics of the telegraph noise generated by reversals of the Ln3+ moment, thereby revealing the nuclear spin state. We observe nuclear spin relaxation times T1 in excess of minutes. Furthermore, we drive nuclear spin transitions using a radio-frequency field and detect the resulting nuclear magnetic resonance directly in the tunneling current. Thus our approach enables fast access to long-lived nuclear spin states in an individual molecule

cond-mat.mes-hall↗

arXiv2023

Gate-tunable topological superconductivity in a supramolecular electron spin lattice

Topological superconductivity emerges in chains or arrays of magnetic atoms coupled to a superconductor. However, the external controllability of such systems with gate voltages is detrimental for their future implementation in a topological quantum computer. Here we showcase the supramolecular assembly of radical molecules on Pb(111), whose discharge is controlled by the tip of a scanning tunneling microscope. Charged molecules carry a spin-1/2 state, as confirmed by observing Yu-Shiba-Rusinov in-gap states by tunneling spectroscopy at millikelvin temperature. Low energy modes are localized at island boundaries with a long decay towards the interior, whose spectral signature is consistent with Majorana zero modes protected by mirror symmetry. Our results open up a vast playground for the synthesis of gate-tunable organic topological superconductors.

cond-mat.supr-con↗

arXiv2022

Wetland Quality as a Determinant of Economic Value of Ecosystem Services: an Exploration

Wetland quality is a critical factor in determining values of wetland goods and services. However, in many studies on wetland valuation, wetland quality has been ignored. While those studies might give useful information to the local people for decision-making, their lack of wetland quality information may lead to the difficulty in integrating wetland quality into a cross-studies research like meta-analysis. In a meta-analysis, a statistical regression function needs withdrawing from those individual studies for analysis and prediction. This research introduces the wetland quality factor, a critical but frequently missed factor, into a meta-analysis and simultaneously considers other influential factors, such as study method, socio-economic state and other wetland site characteristics, as well. Thus, a more accurate and valid meta-regression function is expected. Due to no obvious quality information in primary studies, we extract two kinds of wetland states from the study context as relative but globally consistent quality measurement to use in the analysis, as the first step to explore the effect of wetland quality on values of ecosystem services.

econ.GN↗