报告介绍 Abstract:Bi2Se3 is predicted to be a 3D topological insulator (TI) with a large band gap and a single Dirac cone. Although surface sensitive spectroscopy has revealed the nature of the surface Dirac fermion states in Be2Se3, due to the coexistence of the bulk and surface states, transport evidence of the surface Dirac fermion states has been elusive. In this talk, I will present our effort to tune t...

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报告介绍 Due to the reduced spatial dimensions, many intriguing quantum phenomenon arise in two-dimensional (2D) systems, such as graphene, 2D electron gas (2DEG) in semiconductor heterostructures, and the topologically protected surface state of topological insulator (TI). While transport measurements are traditional ways to study the 2D systems, various surface sensitive probes including scanning tunneling...

报告介绍 Recently, level crossings in the energy bands of crystals have been identified as a key signature for topological phase transitions. I will discuss the criteria that need to be met for level crossings or anticrosssings to occur in quantum systems. In general, three independent parameters must be tuned appropriately to bring two quantum levels into degeneracy. Small perturbations thus easily destroy ...

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报告介绍 Seceond Harmonic Genration (SHG) and two photon luminescence are used to study the surface of metallic nanoparticles. We observed the first direct experimental evidence for the surface generated SHG signal from metallic nanoparticles. This observation clarified the confusion on the origin of the double frequency emission from metallic nanparticles in colloids. The SHG emission was then used to monit...

报告介绍 Semiconductor nanostructures such as quantum dots (QDs) have offered unique opportunities to investigate sophisticated quantum optical effects in a solid-state system. These include quantum interference, Rabi oscillations [1], as well as photon antibunching, and were previously only observable in isolated atoms or ions. In addition, QDs can be readily integrated into optical microcavities, making th...

报告介绍 There have been great interests in recent years on exploring the use of hybrid organic-inorganic nanostructures in various sustainable energy applications including photovoltaics and light-emitting devices (LEDs). Organic electronic materials such as conjugated polymers have advantages in low material cost, tunability in material properties, and compatibility with flexible substrate and roll-to-roll...

报告介绍 In this talk, I shall discuss issues concerning computational modeling of quantum transport properties of nanoelectronics from the atomic point of view, within the framework of density functional theory (DFT) combined with the Keldysh non-equilibrium Green’s functions (NEGF). The goal is to make parameter-free predictions of material specific properties of nanoelectronic devices. The successes...

报告介绍 报告摘要：量子级联激光器是一种利用半导体耦合量子阱子带间的电子跃迁而产生激光的单极性半导体激光器，是基于量子工程设计的、具有级联特征的、波长可大范围调节的中远红外波段激光器，目前的波长范围2.9-300微米，具有小型、高速响应、大功率、可集成等特点。在环境、医学、红外通信等方面具有广泛的应用前景。报告简要介绍量子级联激光器的工作原理和研究现状、中科院半导体所部分研究工作、目前存在的一些科学技术问题等。报告...

报告介绍 Air pollution and global climate change are important environmental issues that affect our society. In order to address these problems and to develop control strategies, advanced detection techniques and deeper understanding of atmospheric chemistry are required. This presentation focuses on (1) developments and applications of cavity ringdown spectroscopy (CRDS) and cavity enhance absorption spectr...

报告介绍 We propose a scheme for coherent rotation of the valley isospin of a single electron confined in a carbon nanotube quantum dot [1]. The scheme exploits the ubiquitous atomic disorder of the nanotube crystal lattice, which induces time-dependent valley mixing as the confined electron is pushed back and forth along the nanotube axis by an applied ac electric field. Using experimentally determined valu...

报告介绍 The negatively charged nitrogen-vacancy (NV-) centers in diamond, with their unique spin and optical properties, have emerged as a promising solid system for studying spin related phenomena. The local spin states of the NV- center can be accessed and manipulated optically at a single-site level, making it suitable for quantum information applications. Despite much research efforts, our understanding...

报告介绍 In this talk, He will summarize their new research on how to use FePt nanoparticles to catalyze H2O2 decomposition within cells for therapeutic applications, and how to apply core/shell M/FePt (M = Pd, NiPd or Au) nanoparticles to improve both activity and durability for the oxygen reduction reaction and methanol oxidation in polymer electrolyte membrane fuel cells.