arXiv subjects

C. Wen

Publications and source records attributed to C. Wen.

10 recordsLinked to original sources

arXiv2026

EBS and in-beam $\gamma$-ray investigation of FCVA-prepared Cr$_2$O$_3$ targets for low-energy $^{16}$O+$^{16}$O fusion experiments

The Cr$_2$O$_3$ solid target for low-energy $^{16}$O+$^{16}$O fusion experiments was fabricated using filtered cathodic vacuum arc (FCVA) deposition. Its composition, oxygen areal density and impurity content were characterized by elastic backscattering spectrometry (EBS), and the impurity-induced background contributions were investigated by in-beam $\gamma$-ray spectroscopy. EBS results indicate that the Cr$_2$O$_3$ film exhibits good stoichiometry and uniformity, with $^{16}$O areal densities ranging from $(3.24-3.25)\times10^{17}$ atoms/cm$^2$. The EBS analysis reveals a carbon atomic fraction of approximately 1.25-1.29\% in the Cr$_2$O$_3$ layer, while a large amount of carbon impurities are also identified on the surface of Cr substrate. In-beam $\gamma$-ray spectra reveal prominent transitions associated with $^{27}$Al and $^{24}$Mg at 844, 1015, and 1369 keV, mainly originating from $^{12}$C+$^{16}$O fusion reactions induced by carbon impurities under $^{16}$O irradiation. Meanwhile, characteristic $\gamma$-rays emissions from evaporation channels of the $^{16}$O+$^{16}$O reaction, including $^{31}$S, $^{31}$P, and $^{28}$Si, were also observed and can be used to extract the $^{16}$O+$^{16}$O fusion cross sections. This work provides an experimental basis for the development of high-purity oxide targets and the optimization of target configurations for future low-background $^{16}$O+$^{16}$O fusion cross section measurements.

physics.ins-det↗

arXiv2025

$\mathcal{N}=2$ Universality at Strong Coupling

We present a detailed analysis of integrated correlators for an $\mathcal{N}=2$ superconformal field theory on a squashed sphere with SU$(N)$ gauge group and fundamental/anti-symmetric matter. Employing the matrix model arising from supersymmetric localisation, we compute derivatives of the partition function $\mathcal{Z}$ with respect to the fundamental mass ($\mu$), the anti-symmetric mass ($m$) and the squashing parameter ($b$), corresponding to integrated insertions of the $\mathcal{N}=2$ flavour-current and stress-tensor multiplets, which are holographically dual to gluon and graviton scatterings in the presence of D7-branes. For correlators dual to only graviton scatterings, we confirm the planar-limit equivalence with $\mathcal{N}=4$ SYM. Our main result is a remarkable universality for the mixed gluon-graviton scattering amplitudes off D7-branes, obtained from $\partial_\mu^2 \partial_m^2 \log \mathcal{Z}$ and $\partial_\mu^2 \partial_b^2 \log \mathcal{Z}$. We show that the leading and sub-leading large-$N$ contributions in the strong-coupling regime are governed by universal asymptotic series, identical to those found for integrated giant-graviton correlators in $\mathcal{N}=4$ SYM. We also propose an $\text{SL}(2, \mathbb{Z})$-invariant completion of these results in terms of non-holomorphic Eisenstein series. This completion provides exact constraints on higher-derivative terms in the dual $\text{AdS}_5$ brane-string amplitudes and highlights an unexpected universality across distinct superconformal theories at strong coupling.

hep-th↗

arXiv2025

Topological Optical Achirality

For arbitrary reciprocal single-mode structures, regardless of their geometric shapes or constituent materials, there must exist incident directions of plane waves for which they are optically achiral.

physics.optics↗

arXiv2025

Graphene Electro-Absorption Modulators for Energy-Efficient and High-Speed Optical Transceivers

The increasing demand for energy-efficient hardware for artificial intelligence (AI) and data centres requires integrated photonic solutions delivering optical transceivers with Tbit/s data rates and energy consumption$<$1pJ/bit. Here, we report double single-layer graphene electro-absorption modulators on Si optimized for energy-efficient and ultra-fast operation, demonstrating 67GHz bandwidth and 80Gbit/s data rate, in both O and C bands, using a fabrication tailored for wafer-scale integration. We measure a data rate$\sim$1.6 times larger than previously reported for graphene. We scale the modulator's active area down to 22$\mu$m$^2$, achieving a dynamic power consumption$\sim$58fJ/bit, $\sim$3 times lower than previous graphene modulators and Mach-Zehnder modulators based on Si or lithium niobate. We show devices with$\sim$0.037dB/V$\mu$m modulation efficiency,$\sim$16 times better than previous demonstrations based on graphene. This paves the way to wafer-scale production of graphene modulators on Si useful for Tbit/s optical transceivers and energy-efficient AI

cond-mat.mtrl-sci↗

arXiv2022

Controlling charge density order in 2H-TaSe$_{2}$ using a van Hove singularity

We report on the interplay between a van Hove singularity and a charge density wave state in 2H-TaSe$_{2}$. We use angle-resolved photoemission spectroscopy to investigate changes in the Fermi surface of this material under surface doping with potassium. At high doping, we observe modifications which imply the disappearance of the $(3\times 3)$ charge density wave and formation of a different correlated state. Using a tight-binding-based approach as well as an effective model, we explain our observations as a consequence of coupling between the single-particle Lifshitz transition during which the Fermi level passes a van Hove singularity and the charge density order. In this scenario, the high electronic density of states associated with the van Hove singularity induces a change in the periodicity of the charge density wave from the known $(3\times 3)$ to a new $(2\times 2)$ superlattice.

cond-mat.str-el↗

arXiv2021

Observation of the near-threshold intruder $0^-$ resonance in $^{12}$Be

A resonant state at $3.21^{+0.12}_{-0.04}$\,MeV, located just above the one-neutron separation threshold, was observed for the first time in $^{12}$Be from the $^{11}$Be\,$(d,p)^{12}$Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^-$, according to the distorted-wave Born approximation (DWBA) and decay-width analysis. Gamow coupled-channel (GCC) and Gamow shell-model (GSM) calculations show the importance of the continuum-coupling, which dramatically influences the excitation energy and ordering of low-lying states. Various exotic structures associated with cross-shell intruding configurations in $^{12}$Be and in its isotonic nucleus $^{11}$Li are comparably discussed.

nucl-ex↗

arXiv2018

Binding-energy independence of reduced single particle strengths derived from $(p,d)$ reactions

An overall reduction factor (ORF) is introduced for studying the quenching of single particle strengths through nucleon transfer reactions. The ORF includes contributions of all the probed bound states of the residual nucleus in a transfer reaction and permits a proper comparison with results of inclusive knockout reactions. A systematic analysis is made with 103 sets of angular distribution data of $(p,d)$ reactions on 21 even-even targets with atomic mass numbers from 8 to 56 using the consistent three-body model reaction methodology proposed in [J. Lee, J.A. Tostevin, B.A. Brown, et al., Phys. Rev. C 73, 044608 (2006)]. The extracted ORFs are found to be nearly independent on the nuclear isospin asymmetry, which is different from the systematics of inclusive knockout reactions but is consistent with the recent measurement of $(d,t)$, $(d,3He)$, $(p,2p)$, and $(p,pn)$ reactions on nitrogen and oxygen isotopes and \textit{ab initio} calculations.

nucl-ex↗

arXiv2018

A New Measurement of the Intruder Configuration in 12Be

A new $^{11}$Be($d,p$)$^{12}$Be transfer reaction experiment was carried out in inverse kinematics at 26.9$A$ MeV, with special efforts devoted to the determination of the deuteron target thickness and of the required optical potentials from the present elastic scattering data. In addition, a direct measurement of the cross sections for the 0$_2^+$ state was realized by applying an isomer-tagging technique. The s-wave spectroscopic factors of 0.20(0.04) and 0.41(0.11) were extracted for the 0$_1^+$ and 0$_2^+$ states, respectively, in $^{12}$Be. Using the ratio of these spectroscopic factors, together with the previously reported results for the p-wave components, the single-particle component intensities in the bound 0$^+$ states of $^{12}$Be were deduced, allowing a direct comparison with the theoretical predictions. It is evidenced that the ground-state configuration of $^{12}$Be is dominated by the d-wave intruder, exhibiting a dramatic evolution of the intruding mechanism from $^{11}$Be to $^{12}$Be, with a persistence of the $N = 8$ magic number broken.

nucl-ex↗

arXiv2009

Tree-Level Amplitudes in N=8 Supergravity

We present an algorithm for writing down explicit formulas for all tree amplitudes in N=8 supergravity, obtained from solving the supersymmetric on-shell recursion relations. The formula is patterned after one recently obtained for all tree amplitudes in N=4 super Yang-Mills which involves nested sums of dual superconformal invariants. We find that all graviton amplitudes can be written in terms of exactly the same structure of nested sums with two modifications: the dual superconformal invariants are promoted from N=4 to N=8 superspace in the simplest manner possible--by squaring them--and certain additional non-dual conformal gravity dressing factors (independent of the superspace coordinates) are inserted into the nested sums. To illustrate the procedure we give explicit closed-form formulas for all NMHV, NNMHV and NNNMV gravity superamplitudes.

hep-th↗

arXiv2004

QCD$_4$ Glueball Masses from AdS-6 Black Hole Description

By using the generalized version of gauge/gravity correspondence, we study the mass spectra of several typical QCD$_4$ glueballs in the framework of AdS$_6$ black hole metric of Einstein gravity theory. The obtained glueball mass spectra are numerically in agreement with those from the AdS$7 \times S^4$ black hole metric of the 11-dimensional supergravity.

hep-th↗