arXiv subjects

Q. Xue

Publications and source records attributed to Q. Xue.

4 recordsLinked to original sources

arXiv2026

Magnetic precession induced spin accumulation in collinear antiferromagnets

Generating and characterizing uniform and staggered spin polarization in antiferromagnets is one of the key challenges for antiferromagnetic spintronic technology. Here, we perform perturbative theory, group-theoretical symmetry analysis, low energy and ab initio simulations to propose that the magnetic precession near the equilibrium magnetic axis could generate finite uniform and staggered spin polarization at the opposite magnetic sublattices (referring to total magnetic and N\'eel vector generation) in a single AFM semiconductors. This response does not require the heterojunction setup and could eliminate the lattice mismatch issues at the junction. Through scrutinizing all symmetrically-protected vanishing magnetic moment groups and especially focusing on parity-time (PT ) invariant groups, we identify the symmetry constraints that describe the staggered spin accumulation responses, and disclose their fieldlike and dampinglike characters. This unravels a hidden spin accumulation mode in AFM semiconductors. Furthermore, we simulate such an effect using a perturbative approach and suggest that electric gate field and Floquet light-dressing can effectively manipulate these responses.

cond-mat.mtrl-sci↗

arXiv2025

Insufficient evidence for DMS and DMDS in the atmosphere of K2-18 b. From a joint analysis of JWST NIRISS, NIRSpec, and MIRI observations

Recent JWST observations of the temperate sub-Neptune K2-18 b have been interpreted as suggestive of a liquid water ocean with possible biological activity. Signatures of DMS and DMDS have been claimed in the near-infrared (using the NIRISS and NIRSpec instruments) and mid-infrared (using MIRI). However, the statistical significance of the atmospheric imprints of these potential biomarkers has yet to be quantified from a joint analysis of the entire planet spectrum. We test the robustness of the proposed DMS/DMDS detections by simultaneously modeling the NIRISS and NIRSpec observations jointly with the MIRI spectrum, considering different data reductions and modeling choices. We use three well-tested pipelines to re-reduce the JWST observations, and two retrieval codes to analyze the resulting transmission spectra as well as previously published data. Our joint analysis of the panchromatic (0.6 - 12 um) spectrum of K2-18 b finds insufficient evidence for the presence of DMS and/or DMDS in the atmosphere of the planet. Furthermore, other molecules containing methyl functional groups (e.g., ethane) with absorption bands similar to DMS/DMDS provide an equally good fit to the data. We find that any marginal preferences are the result of limiting the number of molecules considered in the model and oversensitivity to small changes between data reductions. Our results confirm that there is no statistical significance for DMS or DMDS in K2-18 b's atmosphere. While previous works have demonstrated this on MIRI or NIRISS/NIRSpec observations alone, our analysis of the full transmission spectrum does not support claims of potential biomarkers. Using the best-fitting model including DMS/DMDS on the published data, we estimate that ~25 more MIRI transits would be needed for a 3-sigma rejection of a flat line relative to DMS/DMDS features in the planet's mid-infrared transmission spectrum.

astro-ph.EP↗

arXiv2025

Reversing Neel Vector in PT-Antiferromagnets by Nonreciprocal Light Scattering

Antiferromagnetic (AFM) spintronics has been receiving tremendous attention due to their ultrafast kinetics, zero stray field, immune to external magnetic field, and potential to minimizing magnetic storage devices. The optical control of AFM Neel vector has become a hectic topic during recent years, which could facilitate the AFM utilization in practical systems. In this work, we propose a nonreciprocal light scattering mechanism to flip the Neel vector in parity-time (PT) combined AFM multilayers, by estimating the energy contrast between the bistable Neel polarization configurations. We illustrate our theory using a low energy kp model, and perform ab initio calculations on two typical A-type AFM materials, MnBi2Te4 and CrI3 thin films. We show that varying incident photon frequency could modulate the relative stability between the bistable Neel vector state, which also depends on the light handedness. According to this theory, our parameter-independent calculations on the Neel vector diagram shows consistent predictive results with recent experimental observations. This mechanism provides an effective route to controlling the AFM order parameter through photo-magnetic interaction.

cond-mat.mtrl-sci↗

arXiv2022

A multi-cubic-kilometre neutrino telescope in the western Pacific Ocean

Next-generation neutrino telescopes with significantly improved sensitivity are required to pinpoint the sources of the diffuse astrophysical neutrino flux detected by IceCube and uncover the century-old puzzle of cosmic ray origins. A detector near the equator will provide a unique viewpoint of the neutrino sky, complementing IceCube and other neutrino telescopes in the Northern Hemisphere. Here we present results from an expedition to the north-eastern region of the South China Sea, in the western Pacific Ocean. A favorable neutrino telescope site was found on an abyssal plain at a depth of $\sim$ 3.5km. At depths below 3km, the sea current speed, water absorption and scattering lengths for Cherenkov light, were measured to be $v_{\mathrm{c}}<$10cm/s, $\lambda_{\mathrm{abs} }\simeq$ 27m and $\lambda_{\mathrm{sca} }\simeq$ 63m, respectively. Accounting for these measurements, we present the design and expected performance of a next-generation neutrino telescope, TRopIcal DEep-sea Neutrino Telescope (TRIDENT). With its advanced photon-detection technology and large dimensions, TRIDENT expects to observe the IceCube steady source candidate NGC 1068 with 5$\sigma$ significance within 1 year of operation. This level of sensitivity will open a new arena for diagnosing the origin of cosmic rays and probing fundamental physics over astronomical baselines.

astro-ph.HE↗