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Hunting η-bound nuclei

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Chinese Physics C 2010年第9期34卷 1218-1223页

作者： H.Machner Institut für Kernphysik Forschungszentrum Jülich fakultt für physik Universitt Duisburg-Essen

the η meson can be bound to atomic *** search is discussed in the form of final state interaction for the reactions dp → 3 Heη and dd → 4 Heη.for the latter case tensor polarized deuterons were used in order to extract the s-wave *** both reactions complex scattering lengths are deduced： a 3 Heη = ± 10.7±0.8 ＋0.1 -0.5 ＋i· 1.5±2.6 ＋1.0-0.9 fm and a 4 Heη = [±（3.1±0.5）＋i·（0±0.5）] *** a two-nucleon transfer reaction under quasi-free conditions,p^ 27 Al → ^3 HeX,was *** system X can be the bound 25 Mg  η at *** a possible decay of an intermediate N  （1535） is required,a highly significant bump shows up in the missing mass *** data give for a bound state a binding energy of 13.3±1.6 MeV and a width of σ=4.4±1.3 MeV.

关键词： η meson production η nucleus interaction final state interaction recoil free kinematics

A Brief Overview of Hard-thermal-Loop Perturbation theory

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Communications in theoretical Physics 2012年第3期57卷 409-421页

作者：苏楠 fakultt fr physik Universitt BielefeldD-33615 BielefeldGermany

the poor convergence of quantum field theory at finite temperature has been one of the main obstacles in the practical applications of thermal QCD for *** we briefly review the progress of hard-thermal-loop perturbation theory (HtLpt) in reorganizing the perturbative expansion in order to improve the *** quantum mechanical anharmonic oscillator is used as a simple example to show the breakdown of weak-coupling expansion,and variational perturbation theory is introduced as an effective resummation scheme for divergent weak-coupling *** discuss HtLpt thermodynamic calculations for QED,pure-glue QCD,and QCD with N f=3 up to three-loop *** results suggest that HtLpt provides a systematic framework that can be used to calculate both static and dynamic quantities for temperatures relevant at LHC.

关键词： thermal field theory resummation hard thermal loops

the atomic structure and the properties of Ununbium (Z=112) and Mercury (Z=80)

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Science China(Physics,Mechanics & Astronomy) 2007年第6期50卷 707-715页

作者： S.frItZSCHE B.frICKE Institut fr physik Universita..t Kassel 34132Germany

A super heavy element Uub (z = 112) has been studied theoretically in conjunction with rela-tivistic effects and the effects of electron *** atomic structure and the oscillator strengths of low-lying levels have been calculated,and the ground states have also been determined for the singly and doubly charged ions. the influence of relativity and correlation effects to the atomic properties of such a super heavy element has been investigated in detail. the results have been compared with the properties of an element Hg. two energy levels at wave numbers 64470 and 94392 are suggested to be of good candidates for experimental observations.

关键词： super heavy element atomic structure relativistic effects electron correlation effects MCDf method

Statistical learning of engineered topological phases in the kagome superlattice of AV_(3)Sb_(5)

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npj Computational Materials 2022年第1期8卷 624-629页

作者： thomas Mertz Paul Wunderlich Shinibali Bhattacharyya francesco ferrari roser Valentí Institut für theoretische physik Goethe-UniversitätFrankfurt am MainGermany

recent experimental findings have reported the presence of unconventional charge orders in the enlarged(2×2)unit-cell of kagome metals AV3Sb5(A=K,rb,Cs)and hinted towards specific topological *** by these discoveries,we investigate the types of topological phases that can be realized in such kagome *** this context,we employ a recently introduced statistical method capable of constructing topological models for any generic *** analyzing large data sets generated from symmetry-guided distributions of randomized tight-binding parameters,and labeled with the corresponding topological index,we extract physically meaningful *** illustrate the possible real-space manifestations of charge and bond modulations and associated flux patterns for different topological classes,and discuss their relation to present theoretical predictions and experimental signatures for the AV_(3)Sb_(5)***,we predict higher-order topological phases that may be realized by appropriately manipulating the currently known systems.

关键词： topological signature meaningful

Limits on light emission from silicon

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Chinese Optics Letters 2009年第4期7卷 268-270页

作者： Peter Würfel Institut für Angewandte physik Universitt KarlsruheD-76128 KarlsruheGermany

Although silicon is an indirect semiconductor, light emission from silicon is governed by the same gener- alized Planck＇s radiation law as the emission from direct semiconductors. the emission intensity is given by the absorptance of the volume in which there is a difference of the quasi fermi energies. A difference of the fermi energies may result h＇om the absorption of external light （photoluminescence） or from the injection of electrons and holes via selective contacts （electroluminescence）. the quantum efficiency may be larger than 0.5 for carrier densities below 10^15 cm^-3. At larger densities, non-radiative recombination, in particular Auger recombination dominates. At all carrier densities, the relation between emission intensity and difference of the quasi fermi energies is maintained. Since this difference is equal to the voltage of a properly designed solar cell, luminescence is the key indicator of material quality for solar cells.

关键词： Carrier concentration fermi level Light Light emission Photoluminescence Semiconducting silicon Silicon

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Hadron molecules

Chinese Physics C 2010年第9期34卷 1185-1190页

作者： thomas Gutsche tanja Branz Amand faessler Ian Woo Lee Valery E.Lyubovitskij Institut für theoretische physik Universitt TübingenKepler Center for Astro and Particle Physics

We discuss a possible interpretation of the open charm mesons D＊s0 （2317）,D s1 （2460） and the hidden charm mesons X（3872）,Y（3940） and Y（4140） as hadron *** a phenomenological Lagrangian approach we review the strong and radiative decays of the D＊ s0 （2317） and D s1 （2460） *** X（3872） is assumed to consist dominantly of molecular hadronic components with an additional small admixture of a charmonium *** the radiative （γJ/ψ and γψ（2s）） and strong （J/ψ2π and J/ψ3π） decay modes we show that the present experimental observation is consistent with the molecular structure assumption of the X（3872）.finally,we give evidence for molecular interpretations of the Y（3940） and Y（4140） related to the observed strong decay modes J/ψ＋ω or J/ψ＋φ,respectively.

关键词： charm mesons hadronic molecule strong and radiative decay

tuning two-dimensional electron and hole gases at LaInO_(3)/BaSnO_(3) interfaces by polar distortions,termination,and thickness

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npj Computational Materials 2021年第1期7卷 1584-1591页

作者： Wahib Aggoune Claudia Draxl Institut für physik and IrIS Adlershof Humboldt-Universität zu Berlin12489 BerlinGermany

two-dimensional electron gases(2DEG),arising due to quantum confinement at interfaces between transparent conducting oxides,have received tremendous attention in view of electronic ***,we explore the potential of interfaces formed by two lattice-matched wide-gap oxides of emerging interest,i.e.,the polar,orthorhombic perovskite LaInO_(3)and the nonpolar,cubic perovskite BaSnO_(3),employing first-principles *** find that the polar discontinuity at the interface is mainly compensated by electronic relaxation through charge transfer from the LaInO_(3)to the BaSnO_(3)*** leads to the formation of a 2DEG hosted by the highly dispersive Sn-s-derived conduction band and a 2D hole gas of O-p character,strongly localized inside LaInO_(3).We rationalize how polar distortions,termination,thickness,and dimensionality of the system(periodic or non-periodic)can be exploited in view of tailoring the 2DEG characteristics,and why this material is superior to the most studied prototype LaAlO_(3)/SrtiO_(3).

关键词： termination gases distortion

Machine learning guided high-throughput search of non-oxide garnets

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npj Computational Materials 2023年第1期9卷 1717-1725页

作者： Jonathan Schmidt Hai-Chen Wang Georg Schmidt Miguel A.L.Marques Institut für physik Martin-Luther-Universität Halle-WittenbergD-06099 HalleGermany

Garnets have found important applications in modern technologies including magnetorestriction,spintronics,lithium batteries,*** overwhelming majority of experimentally known garnets are oxides,while explorations(experimental or theoretical)for the rest of the chemical space have been limited in scope.A key issue is that the garnet structure has a large primitive unit cell,requiring a substantial amount of computational *** perform a comprehensive search of the complete chemical space for new garnets,we combine recent progress in graph neural networks with high-throughput *** apply the machine learning model to identify the potentially(meta-)stable garnet systems before performing systematic density-functional calculations to validate the *** discover more than 600 ternary garnets with distances to the convex hull below 100 meV⋅atom−*** includes sulfide,nitride,and halide *** analyze their electronic structure and discuss the connection between the value of the electronic band gap and charge balance.

关键词： structure sulfide oxides

Quantum Impurity Models with Coupled Cluster Method

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Communications in theoretical Physics 2010年第9期54卷 509-517页

作者： Clive Emary tobias Brandes Institut für theoretische physik

We investigate the ground-state properties of the Anderson single impurity model （finite Coulomb impurity repulsion） with the Coupled Cluster Method. We consider different CCM reference states and approximation schemes and make comparison with exact Green＇s function results for the non-interacting model and with Brillouin-Wigner perturbation theory for the full interacting model. Our results show that coupled cluster techniques are well suited to quantum impurity problems.

关键词： strongly correlated electrons Anderson model coupled-cluster method quantum impurity