从物理到大历史 | 本周物理学讲座

1从物理到大历史

报告人：钱致榕

时间：3月22日（周五）15:30

单位：中科院高能物理研究所

地点：主楼C305会议室

高能物理教我们从宏观看问题，从微观解决问题，把人和自然-宇宙看为一体。过去半个多世纪物理、天文、化学、生物、地质、气象、考古等各个学科的进展，使我们有史以来第一次可以探讨从138亿年前宇宙的诞生一直到今天宇宙、太阳系、地球及生物、人类的演化、变迁，建构出宇宙大历史，从而讲出我们的故事。

2Energy Loss Mechanisms in Organic Solar Cells

报告人：Moritz Riede，University of Oxford

时间：3月19日（周二）10:00

单位：中科院物理研究所

地点：A楼3层会议室

Organic solar cells have the potential to revolutionise the way we harness the power of the sun. They are based on earth-abundant non-toxic raw materials and can be processed by inexpensive and scalable production technologies on flexible substrates and on large areas. However, their power conversion efficiency, one of the key solar cell metrics, reaches only about ½ of the dominating commercial technology of today: silicon solar cells. Of these losses, the difference between optical gap and energy at open circuit voltage (Voc) are most significant. Experiments over the past years have shown how important charge transfer (CT) states between electron on the acceptor are in this: these CT states are the precursors for free charge carriers; are the lowest absorbing and emitting states; their energy correlates better with qVoc than with the energy levels of donor and acceptor; they limit the maximum possible Voc; and are the main source of recombination of electrons and holes, hence determining Voc. There are several strategies for reducing these energy losses and a better understanding of their underlying physics has led to new design criteria in the development of materials, showing the way for further increasing efficiencies to values not thought possible a decade ago. By now, organic solar cells are at the step towards commercialisation and may help to solar energy become as ubiquitous as we need it to save the environment.

3The exploration of new physics in the dark sector

报告人：刘佳，芝加哥大学费米研究所

时间：3月19日（周二）10:30

单位：清华大学

地点：理科楼C109

Dark matter contains 85% of the matter density and it is supposed to have a rich structure, same as our complex baryonic world. The dark sector related with the 85% matter density, is defined as particles which do not interact strongly with the Standard Model particles. It contains dark matter as a stable particle, and particles mediating interaction between dark matter and visible sector. Such particles are called dark mediators, whose interaction with visible sector is feeble, thus could be long-lived. We go over the direct, indirect and collider searches for the canonical dark matter candidate, the weakly interacting massive particles. Then we focus on the recent phase-2 upgrade of the LHC detectors, which has planned a timing resolution of 30 ps. We demonstrate that with the timing upgrade of the LHC, it can improve the sensitivity for the long-lived particle searches significantly, comparing with the traditional displaced-vertex methods. Besides the canonical dark matter candidate, we briefly introduce the ultralight dark matter phenomenology, emphasizing an interplay with neutrino physics and a possible solution to small structure problem.

4 Primordial Black Hole (原初黑洞)

报告人：黄庆国，中科院理论物理所

时间：3月19日（周二）12:00

单位：中科院理论物理所

地点：理论所主楼322报告厅

5High-resolution spectroscopic analysis of a large sample of Li-rich giants found by LAMOST

报告人：Yutao Zhou，NAOC

时间：3月19日（周二）12:00

单位：北京大学

地点：first meeting room, KIAA

The discovery of Li-rich giant has casted a new challenges for the standard stellar evolution models. To resolve this issue, the number of Li-rich giants has been updated by the development of worldwide surveys. Taking advantage of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), 44 newly discovered Li-rich giants are reported, which is the largest uniform high resolution sample until now. The high precision of atmospheric parameters and elemental abundances were derived by the spectral synthesis method based on the high-resolution and high signal-to-noise spectra. We perform a detailed analysis of the properties of these targets, including their evolutionary stages, infrared excess, projected rotational velocity (vsini) and the stellar population. We find that: (1) The associated phenomena of the Li-rich giants show that only three of them are rapid rotators and one have IR excess; (2) The Li-rich giants concentrate at the evolutionary status of the RGB bump, the red clump (RC) and the AGB. Our results imply that the origins of Li enrichment are most likely to be associated with the extra mixing in stellar interior, and the external scenario maybe make a minor contribution to the Li enhancement. Moreover, the different Li-rich episodes take place at the corresponding evolutionary stages. 

6Micro-nanofabrication and microneedle

报告人：崔波，滑铁卢大学

时间：3月20日（周三）10:00

单位：中科院物理研究所

地点：M楼236报告厅

This talk will first focus on nanofabrication on non-flat irregular surfaces using electron beam lithography. Two methods will be presented, using evaporated polystyrene e-beam resist, and grafted mono-layer brush resist. Next, I will cover a few applications of nanostructures fabricated by electron beam and nanoimprint lithography, notably metallic nanostructures for plasmonic bio-chemical sensing applications.

Lastly, I will talk about the fabrication and application of microneedles, including out-of-plane hollow microneedles and long in-plane microneedles. Microneedle technologies have recently become interesting for realizing minimally-invasive monitoring system, since it requires only a small area of skin penetrated at a limited depth with minimal pain sensation and tissue damage.

7Gravitational-wave merging events from the dynamics of stellar mass binary black holes around the massive black holes in galactic nuclei

报告人：Fupeng Zhang，Guangzhou Univ

时间：3月20日（周三）12:00

单位：北京大学

地点：KIAA 1st meeting room

The Advanced LIGO have detected a number of gravitational-wave events that caused by merging of stellar mass binary black holes (BBHs). We study the dynamical evolution of stellar mass BBHs in a galactic nucleus that contains a massive black hole (MBH). We performed a comprehensive study of BBH merging events in the galactic nucleus, by considering simultaneously the non-resonant and resonant relaxations of the BBHs, the binary-single encounters of the BBHs with the field stars, the Kozai-Lidov (KL) oscillation, and the close encounters between the BBHs and the central MBH.  As the BBHs are usually heavier than the background stars, they sink to the center by mass segregation, making the KL oscillation an importanteffect in merging BBHs. The binary-single encounters can make BBHs hardening, and thus increase the merging rates significantly. The mergers of BBHs are mainly contributed by galaxies containing MBHs less massive than 10^8 solar masses and the total event rates are likely in orders of 1-10 /Gpc^3/yr,depending on the detailed assumptions of the nucleus clusters. About 3-10% of these BBH mergers have eccentricities >0.01 when their gravitational wave oscillating frequencies enter the LIGO band (10 Hz). Our results show that merging the BBHs within galactic nuclei can be an important source of the merging events detected by the Advanced LIGO/Virgo, and they can be distinguished from BBH mergers from the galactic fields and globular clusters when enough events are accumulated.

8Aspects on Entanglement Contour I: in Quantum Information Theories

报告人：Qiang Wen，Southeast University

时间：3月20日（周三）14:30

单位：中科院理论物理所

地点：Room 6420, ITP NEW BUILDING

Entanglement contour characterizes the spatial structure of entanglement and quantifies the contribution from the degrees of freedom in any subset of the region A to the total entanglement entropy. Recently I gave a simple proposal for entanglement contour that involves the entanglement entropies of all the subsets inside A. In this talk I will explicitly discuss this proposal and show why it is reasonable and how can we apply it.

9Disentangling the formation of galactic structures through a population-orbit superposition model

报告人： Ling Zhu，SHAO

时间：3月21日（周四）14:00

单位：清华大学

地点：蒙民伟科技南楼S727

Stellar kinematics is a fossil record of galaxy formation and evolution. In particular, the fraction of stars on approximately circular and co-planar orbits, compared to the fraction of stars on kinematically hotter and geometrically rounder orbits, speaks directly to the slowly accretion of gas flow or violent merging/feedback of the galaxies’ past. On the other hand, stars conserve chemical properties since their birth, chemistry is a widely-used indication of stellar age. The combination of stellar kinematics and stellar chemical age may provide us unprecedented information to understand the formation of galactic structures.

The IFU surveys, like CALIFA and MaNGA, provide us information integrated along the line-of-sight, including the surface brightness, kinematic maps, mean age and metallicity maps from stellar-population synthesis of the spectra across the 2D sky-plane.

Using the orbit-superpostion Schwarzschild method, we have been able to derive the internal stellar orbit distribution for a sample of 300 CALIFA galaxies, which form an orbit-based ‘dynamical Hubble sequence’.

Decomposition of different orbital structures is thus possible based on the orbit distribution. In order to obtain chemical information of these orbital structures, we further develop a population-orbit superposition model, by tagging age and metallicities to the orbits in the Schwarzschild model. This is an on-going work, I will show you various method-tests and some preliminary results on the CALIFA galaxies.

10Theoretically Tracing Topological States: from crystals to quasicrystals and amorphous systems

报告人：黄华卿，犹他大学

时间：3月21日（周四）14:00

单位：北京师范大学

地点：物理楼106

Since the remarkable discovery of topological insulators, the electronic-structure topology of quantum materials has emerged as a new frontier in modern condensed matter physics and material science. Novel macroscopic quantum phenomena of topological materials are not only of fundamental interest, but may hold some potential for technological applications. In this talk, I will briefly introduce several works about novel topological states (including various topological insulators and semimetals) in crystalline materials, some of which have already experimental verified. And I will also discuss the materials engineering of controlling topological phase transition (TPT) in topological materials. Then, I will expend the horizon of topological states to a new territory, the quasicrystals, and define a new topological invariant, the spin Bott index, to identify nontrivial topology in aperiodic and amorphous systems. Finally, I develop a unified view of TPTs in solids by devising a general topological band theory that underlines a universal linear scaling of TPTs in crystalline, quasicrystalline and amorphous systems.

112D Spin-Orbit Coupling with Ultracold Quantum Gas

报告人：陈帅，中国科学技术大学

时间：3月21日（周四）16:00

单位：清华大学

地点：理科楼郑裕彤讲堂

Spin-Orbit (SO) coupling, as a fundamental quantum effect, is an essential ingredient in many topological phases of quantum matters, like topological insulator and topological semiconductor. To synthesize 2-dimensional (2D) SO coupling with ultracold quantum gases is one of the keys in the field of quantum simulation to study topological quantum matters. We report here the realization of a robust and highly controllable 2D SO coupling with topological non-trivial band structure. By applying a retro-reflected 2D optical lattice, the synthesized 2D SO coupling has precise inversion and C4 symmetries. The non-trivial band topology of the 2D SO coupling is precisely addressed by both equilibrium and non-equilibrium processes. Winding numbers and topological charges are also extracted from the post-quench evolution. Novel dynamical topological quantum matter is also synthesized. Our studies open the new avenue in quantum simulation to explore exotic topological matters with non-equilibrium dynamics.

12Anti-triplet charmed baryon decays with SU(3) flavor symmetry

报告人：Yu-Kuo Hsiao，Shanxi Normal University

时间：3月22日（周五）10:00

单位：中科院高能物理所

地点：B326 main building

In this talk, I would like to present the studies of Bc->BnM, BnMM’ and BnV with SU(3) flavor symmetry, where Bc denotes the anti-triplet charmed baryon states of (Xi^0_c, Xi^+_c, Lambda^+_c), and M(V) the pseudo-scalar (vector) meson ones. Particularly, I will show our recent predictions for the branching fractions of Lambda^+_c->BnV, which are accessible to the BESIII experiment.

13A New Insight into Forming Jupiter’s Dilute Core

报告人：Shangfei Liu，Sun Yat-sen Univ

时间：3月22日（周五）12:00

单位：北京大学

地点：1st meeting room, KIAA

The Juno spacecraft has measured Jupiter's gravitational field to an unprecedented precision. These data suggest that Jupiter could have a diluted (low mean-density) core over 40% of its radius. Despite the large mass (an order of magnitude larger than that of the Earth) of heavy elements (other than hydrogen and helium) in the core, its spatial spread poses a challenge to the conventional Jupiter formation model based on the assumption of runaway gas accretion onto a distinct heavy-element core. While Jupiter's original rocky/metallic core could have been subsequently eroded by its surrounding convective gaseous envelope, it is unlikely for most of its mass to have diffused over such an extended region during the past 4.56 Gyr. With a series of 3D hydrodynamic simulations, we show that sufficiently energetic collisions between additional planetary embryos and the newly emerged Jupiter can shatter its primordial heavy-element compact core and mix the heavy elements with the outer envelope. This leads to an internal structure consistent with the diluted core scenario which is also found to persist over billions of years. A similar event may have also occurred for Saturn. We suggest that different mass and speed of the intruding embryo may have contributed to the structural dichotomy between Jupiter and Saturn.

14机器学习在探索新物理中的应用

报告人：杨金民

时间：3月22日（周五）18:30

单位：中国科学院大学

地点：雁栖湖校区 教1-009

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