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2,845 results on '"Yang, Jianping"'

3. Reversal of Orbital Hall Conductivity and Emergence of Tunable Topological Quantum States in Orbital Hall Insulator

Author

Ji, Shilei, Quan, Chuye, Yao, Ruijia, Yang, Jianping, and Li, Xing'ao

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Quantum Physics
Abstract

Recent findings indicate that orbital angular momentum (OAM) has the capability to induce the intrinsic orbital Hall effect (OHE), which is characterized by orbital Chern number in the orbital Hall insulator. Unlike the spin-polarized channel in Quantum anomalous Hall insulator, the OAM is valley-locked, posing challenges in manipulating the corresponding edge state. Here we demonstrate the sign-reversal orbital Chern number through strain engineering by combing the $k \cdot p$ model and first-principles calculation. Under the manipulation of strain, we observe the transfer of non-zero OAM from the valence band to the conduction band, aligning with the orbital contribution in the electronic structure. Our investigation reveals that electrons and holes with OAM exhibit opposing trajectories, resulting in a reversal of the orbital Hall conductivity. Furthermore, we explore the topological quantum state between the sign-reversible OHE.

Published
2023
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11. Constraints on Extragalactic Background Light using TeV Observations of BL Lacertae objects

Author

Qin, Longhua, Wang, Jiancheng, Gao, Quangui, Na, Weiwei, Li, Huaizhen, Wang, Ao, Yang, Chuyuan, and Yang, Jianping

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

The extragalactic background light (EBL) in the IR to UV bands partly absorbs very high energy (VHE, $E \geq$ 100GeV) $\gamma-$ray photons travelling over cosmological distances via pair production. In this paper, to get stronger constraints on EBL, we use the deliberate selection of the EBL model and data of five BL Lacs with better statistics and the harder spectra to limit the EBL density and the radiation mechanism of BL Lacs. We constrain the upper limit of the EBL density by fitting the spectral energy distributions (SEDs) of TeV BL Lacs and find that our results are compatible with the published measurement, reaching 50 $\rm{nW m^{-2} sr^{-1}}$. We also obtain that the EBL is not necessarily transparent to high VHE photons. We fix the intrinsic spectral index $\Gamma_i$ of TeV BL Lacs as 1.0 and 1.5 under observation evidence and model assumption. Comparing the EBL density given by galaxy count and $Spitzer$ observations, we then obtain that 1ES 1101-232 has $\Gamma_i$ $\leq$ 1.0 and 1ES 0229+200 should have $\Gamma_i$ not harder than 1.0. We demonstrate that the common radiation assumption of BL Lacs, in which the $\Gamma_i$ is softer than 1.5, should be revisited. Furthermore, we propose that the upper EBL density could be given by fitting the hardest energy spectra of TeV BL Lacs., Comment: Accepted by MNRAS

Published
2023
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