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Modelling one-dimensional magnetism and optics

Date: 2019-08-26
Time: 10:00
Venue: M253
Speaker: Wei Wu

报告摘要:One-dimensional physics is fascinating as it can be a good platform for a variety of interesting physcs such as Haldane’s topological phase and Majorana particle. My talk will fall into two parts. In the first part, I will talk about the theoretical description of the magnetic properties of spin-chain compounds, including metal-phthalocyanines (MPc) – a typical organic chain compound, and Sr3NiIrO6. I will discuss the theoretical results for the exchange interactions in MPc based on hybrid-exchange density-functional theory, and compare them with the experimental SQUID measurements. Moreover, I will discuss the linear-spin-wave modelling of the inelastic neutron scattering spectra, where we can see a double-peak structure and energy gap due to the exchange anisotropy, in agreement with the recent first-principles calculations. In the second part, I will talk about the theoretical description of the optical properties of MPc. I will discuss the theoretical results based on the time-dependent density-functional theory for a molecular dimer, and compare them with the experimental UV-Vis measurements, where we can see clearly the agreement and discrepancy between them. Moreover, I will discuss the recent development of a tight-binding excitonic model combining the intra-molecular excitation and charge-transfer states to interpret the absorption spectra more accurately as compared with the dimer model. We also show the potential of molecular chain as a platform for one-dimensional bosonic topological phases. In addition, I will discuss the theoretical modelling of optical spectra of donor linear array in silicon, which is important for developing silicon-based quantum technologies. We will discuss the interesting physics for charge-transfer excitations and their interaction with excitations of other types. The excitation energy goes down to below 10 meV, well in the Thz region, suggesting their potential application in Thz and long-wavelength optics. From the multi-valley calculations, we can also see the effects of central-cell corrections and inter-valley couplings on the charge-transfer excited states.

报告人简介:Wei Wu(武威):2000年吉林大学本科毕业,2003年于中科院理论物理研究所获得硕士学位, 2007年博士毕业于英国伦敦大学学院,之后先后在伦敦纳米中心和伦敦帝国理工学院做研究工作。主要科研内容包括无机半导体中的杂质团簇和有机半导体以及有机大分子的光磁和含时理论,以及这些材料在量子计算,量子模拟,自旋电子学中的应用。