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Martin Bojowald 《Pramana》2004,63(4):765-776
Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like
cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to
the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from
general relativity. The quantum theory is free of singularities, and there are new phenomenological scenarios for the evolution
of the very early universe such as inflation. We give an overview of the main effects, focussing on recent results obtained
by different groups. 相似文献
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Zhi-Huan Li Jian-Ling Lou Qi-Te Li Yu-Cheng Ge Zhe-Wei Yin Yan-Lin Ye 《Frontiers of Physics》2013,8(5):548-554
Particle detection technologies have been largely advanced in ,boratory over the past decade. A neutron sphere was built to detect the decay neutron emitted from the implanted unstable nu eleus, whereas a multi-neutron correlation spectrometer was implemented to detect the forward moving neutrons resulting from breakup reactions. Charged particle telescopes are now equipped with double sided Silicon strip detectors which have excellent energy and position resolutions. Large size gas chambers, such as resistive plate chambers, have been developed in order to achieve high Derformances related to timing or position measurements. The advances of these technologies con tribute substantially to such large science project, as LHC-CMS, and to the experiments with the radioactive nucleus beams. 相似文献
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Colloidal quantum dot(CQD) solar cells have attracted great interest due to their low cost and superior photo-electric properties. Remarkable improvements in cell performances of both quantum dot sensitized solar cells(QDSCs) and PbX(X = S, Se) based CQD solar cells have been achieved in recent years, and the power conversion efficiencies(PCEs) exceeding 12% were reported so far. In this review, we will focus on the recent progress in CQD solar cells. We firstly summarize the advance of CQD sensitizer materials and the strategies for enhancing carrier collection efficiency in QDSCs, including developing multi-component alloyed CQDs and core-shell structured CQDs, as well as various methods to suppress interfacial carrier recombination. Then, we discuss the device architecture development of PbX CQD based solar cells and surface/interface passivation methods to increase light absorption and carrier extraction efficiencies. Finally, a short summary, challenge, and perspective are given. 相似文献
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Nataliya N. Karaush Valentina A. Minaeva Hans Ågren Boris F. Minaev 《Molecular physics》2017,115(17-18):2218-2230
ABSTRACTThis mini-review presents recent advances in theory of electronic and spectral properties of hetero[8]circulenes used as promising fluorescent emitters for organic light-emitting diodes. Special attention is paid to the possibility of their further functionalisation into one-dimensional and two-dimensional (2D) materials. Such materials are predicted to be useful ambipolar organic semiconductors showing high charge carrier mobility. The porous structure of hetero[8]circulene-based nano-arrays can also provide suitable hydrogen storage materials, biomimetic-type nanopores and ionic channels. They serve as a good example of the density functional theory application for design of stable 2D structures, which extends the family of graphene-like materials. 相似文献
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2005年国家自然科学基金的各项评审工作已经基本结束,我们在此向所有关心和支持物理科学一处工作的广大科研工作者表示衷心的感谢!年底将至,我们将就科学处全年的评审工作情况向大家做一个汇报,对在评审中发现的一些问题提出一些建议,希望能对下一年度的项目申请有所帮助. 相似文献
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在清华大学物理系成立60周年之际,我们对近年来清华大学物理系量子信息研究的主要进展情况作一介绍,包括量子搜索算法研究,核磁共振量子计算的实验研究,量子通讯的理论与实验研究.在量子搜索算法研究方面,我们提出了量子搜索算法的相位匹配,纠正了当时的一种错误观点,并且提出了一种成功率为100%的量子搜索算法,改进了Grover算法;在核磁共振量子计算实验方面,我们实现了2到7个量子比特的多种量子算法的实验演示;在量子通讯方面,我们提出了分布式传输的量子通讯的思想,应用于量子密钥分配、量子秘密共享、量子直接安全通讯等方面,构造了多个量子通讯的理论方案.在实验室,我们实现了2米距离的空间量子密码通讯的演示实验. 相似文献
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Recent progress of infrared photodetectors based on lead chalcogenide colloidal quantum dots 下载免费PDF全文
《中国物理 B》2019,(2)
Commercial photodetectors based on silicon are extensively applied in numerous fields. Except for their high performance, their maximum absorption wavelength is not over than 1100 nm and incident light with longer wavelengths cannot be detected; in addition, their cost is high and their manufacturing process is complex. Therefore, it is meaningful and significant to extend absorption wavelength, to decrease cost, and to simplify the manufacturing process while maintaining high performance for photodetectors. Due to the properties of size-dependent bandgap tunability, low cost, facile processing,and substrate compatibility, solution–processed colloidal quantum dots(CQDs) have recently gained significant attention and become one of the most competitive and promising candidates for optoelectronic devices. Among these CQDs, lead chalcogenide CQDs are getting very prominent and are widely investigated. In this paper, the recent progress of infrared(IR) photodetectors based on lead sulfide(PbS), lead selenide(PbSe), and ternary PbS_x Se_(1-x) CQDs, and their underlying concepts, breakthroughs, and remaining challenges are reviewed, thus providing guidance for designing high-performance quantum-dot IR photodetectors. 相似文献
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自旋电子学研究与进展 总被引:3,自引:0,他引:3
自旋电子学是最近几年在凝聚态物理中发展起来的新学科分支,它研究在固体中自旋自由度的有效控制和操纵,在金属和半导体中自旋极化、自旋动力学、自旋极化的输运和自旋电子检测.由于它在信息存储方面的重大应用前景,受到学术界和工业界的高度重视.文章扼要地介绍了自旋电子学发展的历程和发展中的最重要的发现.最近几年,最奇特的发现和最重要的应用莫过于巨磁电阻,薄膜领域纳米技术的迅速发展使巨磁电阻的应用变成可能.作为磁记录头它已使硬磁盘的记录密度提高到170Gbit/in2.动态随机存储器MRAM的研究已实现16Mbit的存储密度. 相似文献
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Graphene quantum dots (GQDs) not only have potential applications on spin qubit, but also serve as essential platforms to study the fundamental properties of Dirac fermions, such as Klein tunneling and Berry phase. By now, the study of quantum confinement in GQDs still attract much attention in condensed matter physics. In this article, we review the experimental progresses on quantum confinement in GQDs mainly by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Here, the GQDs are divided into Klein GQDs, bound-state GQDs and edge-terminated GQDs according to their different confinement strength. Based on the realization of quasi-bound states in Klein GQDs, external perpendicular magnetic field is utilized as a manipulation approach to trigger and control the novel properties by tuning Berry phase and electron–electron (e–e) interaction. The tip-induced edge-free GQDs can serve as an intuitive mean to explore the broken symmetry states at nanoscale and single-electron accuracy, which are expected to be used in studying physical properties of different two-dimensional materials. Moreover, high-spin magnetic ground states are successfully introduced in edge-terminated GQDs by designing and synthesizing triangulene zigzag nanographenes. 相似文献
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人工合成金刚石研究进展 总被引:2,自引:0,他引:2
1796年英国科学家S.Tennant的精确燃烧实验,首次揭示金刚石是由纯碳构成的宝石,从此人类开始了漫长的人工合成金刚石的探索.金刚石通常只能在极端条件下形成,因此,合成技术的突破是人类合成水平提高的一个重要标志,文章对这一领域一些重要工作做了简单回顾,也讨论了作者在合成金刚石方面的工作.我们在440℃的低温条件下,用碱金属(Li,Na,K)还原超临界CO2,得到透明、大尺寸的金刚石晶体,首次实现了金刚石燃烧实验的逆过程,即把低能、直线型CO2分子变成了碳-碳四面体连接的金刚石,开辟了人工合成金刚石的新途径.也讨论了它与天然金刚石起源之间的可能联系. 相似文献
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1796年英国科学家S.Tennant的精确燃烧实验,首次揭示金刚石是由纯碳构成的宝石,从此人类开始了漫长的人工合成金刚石的探索.金刚石通常只能在极端条件下形成,因此,合成技术的突破是人类合成水平提高的一个重要标志,文章对这一领域一些重要工作做了简单回顾,也讨论了作者在合成金刚石方面的工作.我们在440℃的低温条件下,用碱金属(Li,Na,K)还原超临界CO2,得到透明、大尺寸的金刚石晶体,首次实现了金刚石燃烧实验的逆过程,即把低能、直线型CO2分子变成了碳-碳四面体连接的金刚石,开辟了人工合成金刚石的新途径.也讨论了它与天然金刚石起源之间的可能联系. 相似文献
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随着新兴光学设备对微型化、一体化、智能化光学变焦系统的需求与日俱增,大大促进了纳米光电子学的迅猛发展。超构透镜是由具有特殊电磁属性的人造元素按照一定的排列方式组成的具有透镜功能的二维平面结构,其最大优点就是:轻薄和易于集成。然而,集成在超构透镜上的微纳结构一旦制备完成,便难以再改变其形貌或者尺寸,因而无法对其聚焦性能进行实时调控,限制了其功能及应用范围的进一步扩展。近年来,科学家们探索了实现超构透镜聚焦性能实时调控的多种途径,其中最引人注目的是将智能材料与超构透镜相结合。本文首先回顾了可调谐超构透镜的最新进展,分别详细阐述和分析了它们的调节原理和器件性能。最后,归纳分析了当前阻碍可调谐超构透镜发展的主要问题,并进一步对未来可调谐超构透镜的发展趋势做出了展望。 相似文献
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The field of medical photonics is rapidly expanding, and a wide variety of optical technologies and instruments have recently
been developed for diagnostic, therapeutic and basic science applications in medicine. This review presents the recent advances
and application of medical photonics, and the obtained results from our laboratory are highlighted. Finally, the challenges
and future prospects for the transition from technological exploration to clinical studies are discussed.
Supported by the National Natural Science Foundation of China (Grant No. 60678054), the PhD Program Foundation of Ministry
of Education (Grant No. 200803940001), the Key Grants from Ministry of Education (Grant No. 209063), and the Fujian Provincial
Natural Science Foundation (Grant No. 2008J0001) 相似文献