《自然》（20240801出版）一周论文导读
Nature, Volume 632 Issue 8023, 1 August 2024
《自然》第632卷，8023期，2024年8月1日
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物理学Physics
Dirac mass induced by optical gain and loss
光学增益和损耗引起的狄拉克质量
▲ 作者：Letian Yu, Haoran Xue, Ruixiang Guo, Eng Aik Chan, Yun Yong Terh, Cesare Soci, Baile Zhang & Y. D. Chong
▲链接：
https://www.nature.com/articles/s41586-024-07664-x
▲摘要：
质量通常被认为是物质的内在属性，但现代物理学揭示粒子质量有着复杂的起源，例如高能物理学中的希格斯机制。在像石墨烯这样的晶格中，相对论性狄拉克粒子可以以低能准粒子的形式存在，其质量是由晶格对称破缺扰动赋予的。这些产生质量的机制都假定了厄米性，或者说是能量守恒。
利用光子合成晶格，作者通过实验证明了基于光学增益和损耗的非厄米微扰可以产生狄拉克质量。他们探讨了增益和损失诱导狄拉克质量的时空工程如何影响准粒子。研究表明，准粒子在空间边界处经历克莱因隧穿，但非厄米对称的局部破缺可以在畴壁处产生新的通量非守恒效应。
在狄拉克质量符号突然翻转的时间边界上，研究者观察到时间反射现象的一种变体：在非相对论性极限下，狄拉克准粒子的速度反转，而在相对论性极限下，原始速度保持不变。
▲ Abstract：
Mass is commonly considered an intrinsic property of matter, but modern physics reveals particle masses to have complex origins1, such as the Higgs mechanism in high-energy physics. In crystal lattices such as graphene, relativistic Dirac particles can exist as low-energy quasiparticles with masses imparted by lattice symmetry-breaking perturbations. These mass-generating mechanisms all assume Hermiticity, or the conservation of energy in detail. Using a photonic synthetic lattice, we show experimentally that Dirac masses can be generated by means of non-Hermitian perturbations based on optical gain and loss. We then explore how the spacetime engineering of the gain and loss-induced Dirac mass affects the quasiparticles. As we show, the quasiparticles undergo Klein tunnelling at spatial boundaries, but a local breaking of a non-Hermitian symmetry can produce a new flux non-conservation effect at the domain walls. At a temporal boundary that abruptly flips the sign of the Dirac mass, we observe a variant of the time-reflection phenomenon: in the non-relativistic limit, the Dirac quasiparticle reverses its velocity, whereas in the relativistic limit, the original velocity is retained.
A hot-Jupiter progenitor on a super-eccentric retrograde orbit
超偏心逆行轨道上的热木星祖星
▲ 作者：Arvind F. Gupta, Sarah C. Millholland, Haedam Im, Jiayin Dong, Jonathan M. Jackson, Ilaria Carleo, Jessica Libby-Roberts, Megan Delamer, Mark R. Giovinazzi, Andrea S. J. Lin, Shubham Kanodia, Xian-Yu Wang, Keivan Stassun, Thomas Masseron, Diana Dragomir, Suvrath Mahadevan, Jason Wright, Jaime A. Alvarado-Montes, Chad Bender, Cullen H. Blake, Douglas Caldwell, Caleb I. Ca?as, William D. Cochran, Paul Dalba, …Carl Ziegler Show authors
▲链接：
https://www.nature.com/articles/s41586-024-07688-3
▲摘要：
巨大的系外行星绕着其主恒星运行，不太可能形成它们现在的形状。相反，这些“热木星”行星被认为是从冰线以外向内迁移的，并且提出了几种可行的迁移通道，包括通过与第三个天体的角动量交换来激发偏心，然后是潮汐驱动的轨道圆化。
极偏心(e = 0.93)的巨型系外行星HD 80606 b的发现提供了观测证据，证明热木星可能是通过这种高偏心潮汐迁移路径形成的。然而，尚未发现类似的热木星祖先，模拟预测影响这一机制有效性的一个因素是系外行星的质量，因为低质量的行星更有可能在近天通道期间被潮汐破坏6。
研究者介绍了对TIC 241249530 b的光谱和光度观测结果，这是一颗高质量的、轨道偏心率e=0.94的温暖木星。TIC 241249530 b的轨道与离心振荡的历史和未来的潮汐圆化轨迹一致。研究对变暖木星人口的质量和偏心率分布的分析进一步揭示了高质量和高偏心率之间的相关性。
▲ Abstract：
Giant exoplanets orbiting close to their host stars are unlikely to have formed in their present configurations1. These ‘hot Jupiter’ planets are instead thought to have migrated inward from beyond the ice line and several viable migration channels have been proposed, including eccentricity excitation through angular-momentum exchange with a third body followed by tidally driven orbital circularization. The discovery of the extremely eccentric (e?=?0.93) giant exoplanet HD?80606?b provided observational evidence that hot Jupiters may have formed through this high-eccentricity tidal-migration pathway. However, no similar hot-Jupiter progenitors have been found and simulations predict that one factor affecting the efficacy of this mechanism is exoplanet mass, as low-mass planets are more likely to be tidally disrupted during periastron passage6,7,8. Here we present spectroscopic and photometric observations of TIC?241249530?b, a high-mass, transiting warm Jupiter with an extreme orbital eccentricity of e?=?0.94. The orbit of TIC?241249530?b is consistent with a history of eccentricity oscillations and a future tidal circularization trajectory. Our analysis of the mass and eccentricity distributions of the transiting-warm-Jupiter population further reveals a correlation between high mass and high eccentricity.
High-performance 4-nm-resolution X-ray tomography using burst ptychography
高性能的纳米分辨率X射线断层扫描
▲ 作者：Tomas Aidukas, Nicholas W. Phillips, Ana Diaz, Emiliya Poghosyan, Elisabeth Müller, A. F. J. Levi, Gabriel Aeppli, Manuel Guizar-Sicairos & Mirko Holler
▲链接：
https://www.nature.com/articles/s41586-024-07615-6
▲摘要：
