arXiv subjects

Jiang-Tao Liu

Publications and source records attributed to Jiang-Tao Liu.

At least 19 recordsLinked to original sources

arXiv2026

The trigger and localization system of SVOM-GRM

The Space multi-band Variable Object Monitor (SVOM) is an astronomical satellite jointly developed by China and France, primarily focused on the detection of gamma-ray bursts (GRBs) and transient sources. The SVOM satellite was launched on 22nd June, 2024 with four payloads installed onboard. As one of payload, GRM comprises 3 gamma-ray detectors (each detector has an effective area of approximately 200~cm$^{2}$) with distinct pointing directions, enabling the temporal and spectral measurements as well as localization of GRBs in the energy range of 15-5000 keV. This article firstly introduces the on-board localization algorithm design for GRM and presents preliminary test results. Then, leveraging abundant ground-based computational resources, a joint fitting method for spectral and localization analysis using Monte Carlo Markov Chain (MCMC) is implemented. In contrast to the on-board localization algorithm, the on-ground MCMC method comprehensively considers the influence of spectral characteristics, thereby mitigating systematic biases. Finally, a systematic analysis based on this method is provided, highlighting the localization and spectral measurement capabilities of GRM. The preliminary localization analysis result for the on-board detected GRB 240629A by both GRM and Fermi/GBM shows that the localization result (error$\sim$4.14$^{\circ}$) of GRM is consistent with the Fermi/GBM result.

astro-ph.IM↗

arXiv2026

Study on the detector energy response of SVOM/GRM

The SVOM mission is specifically designed to for the detection and localization of Gamma-Ray Bursts (GRBs) and subsequent follow-up observations. Among the four telescopes installed on the SVOM satellite, the Gamma-Ray Monitor (GRM) plays a crucial role in capturing the prompt emission of GRBs due to its wide field of view (FOV) and broad energy range. Accurate determination of the detector's energy response is vital for analyzing GRM data, particularly considering the significant impact of the atmospheric albedo effect on this response. This research focuses on deriving the detector's energy response and establishing a calibration database for the GRM, with particular emphasis on investigating the atmospheric albedo effect. The study shows that the contribution of albedo photons to the detector's effective area depends strongly on the orientation of the GRD line of sight (LoS) relative to Earth and on the incident direction of the GRB. When the GRD LoS is anti-Earth oriented, the albedo effect is minimal, with the highest proportion of albedo effective area accounting for approximately 10% of the total effective area. This occurs when the incident angle of the GRB is nearly perpendicular to the LoS. Conversely, if the GRD LoS is not pointing away from Earth and the GRB arrives from angles greater than about 90$^{\circ}$, the albedo component can become predominant, contributing up to around 100% of the total effective area. This is especially pronounced in the 8-20 keV range, where the direct effective area drops to zero due to the large GRB injection angle. Our results show that, it is necessary for GRM to consider the atmospheric albedo effects in detector response, otherwise the spectral and localization analyses will result in biased measurements.

astro-ph.HE↗

arXiv2026

The Gamma-Ray Monitor onboard the SVOM satellite

The Gamma-Ray Monitor (GRM) is a key scientific payload onboard the Space-based Multi-band Variable Object Monitor (SVOM) satellite, designed specifically for the detection and study of gamma-ray bursts (GRBs). Launched into a 625 km low-Earth orbit on 22 June 2024, GRM serves as a large-area, wide-field-of-view instrument capable of observing the hard X-ray and soft gamma-ray emissions in the energy range of 15 keV to 5 MeV. Its primary scientific objectives include: promptly triggering and localizing GRBs (with particular sensitivity to short-hard GRBs), measuring spectral and temporal properties of bursts, monitoring charged particle fluxes in orbit. GRM successfully detected its first GRB (GRB 240627B) on 27 June 2024, and has since maintained a detection rate of more than 100 GRBs per year. Cross-instrument comparisons with detectors such as GECAM and Fermi/GBM have validated the performance and data quality of GRM. This paper provides a comprehensive overview of GRM instrument design, reliability verification through ground testing, in-orbit triggering and localization algorithms, performance calibration, and preliminary in-orbit results, demonstrating its capability as a versatile gamma-ray all-sky monitor.

astro-ph.IM↗

arXiv2026

GRM Scientific Pipeline

The Gamma-Ray Monitor (GRM) is a key payload of the Space-based multiband astronomical Variable Objects Monitor (SVOM) mission, which is designed to detect gamma ray bursts (GRBs) within the energy range of 15 keV to 5 MeV. The GRM Instrument Center (GRM\_IC) features real-time data processing through the X-band, enabling rapid response of high-energy GRB events. The system employs an event-driven architecture and distributed design, achieving efficient processing and real-time monitoring of massive observational data. Through comprehensive data production processes and scientific data product management, the system achieves efficient production of scientific data products of the L1B / C level through the submission of jobs to the task scheduling system. Through modular architecture design and automated processing workflow, the GRM data processing system realizes precise conversion and scientific analysis of GRB detection data, providing robust technical support for future system upgrades and cross-platform collaboration.

astro-ph.IM↗

arXiv2026

Design and preliminary performance study of the broad-band spectrometer detector for POLAR-2

POLAR-2, the successor of the POLAR experiment aboard China's Tiangong-2 space lab, is set to be deployed on the China Space Station. The POLAR-2 mission aims to conducting high-precision polarization measurements of high-energy transients with a primary focus on Gamma-Ray Bursts (GRBs), following POLAR's pioneering accurate polarization measurements of GRB prompt emission. One of the key advancements in POLAR-2 is the inclusion of a dedicated Broad-band Spectrometer Detector (BSD) instrument, designed to provide precise measurements of GRB location and spectral parameters, which are critical inputs for accurate polarization analysis of POLAR-2's dedicated High-energy Polarimetry Detector (HPD), which is made of plastic scintillator bars array. BSD employs a coded-aperture mask imaging technique and pixelated GAGG scintillation crystals, offering a wide half-coded field of view of ~132° x 125° and an operational energy range of 10-1000 keV. Simulation results indicate that the instrument can achieve a localization accuracy of approximately 1.5° for faint GRBs similar to GRB 170817A, satisfying the core requirements of GRB polarimetry with HPD. BSD also has moderate capability for GRB polarimetry, particularly at several hundred keV energy. This paper outlines the preliminary design of BSD and presents an overall evaluation of its expected scientific performance, based on extensive Monte Carlo simulations and preliminary ground-based calibration tests.

astro-ph.IM↗

arXiv2024

Gravitational Wave-Sensitive Photonic-Like Electronic Transport in Graphene for Efficient High-Frequency Gravitational Wave Detection

High-frequency gravitational waves are crucial for understanding the very early universe and distinguishing between various cosmological models, but detecting them remains a significant challenge. We investigated the effects of high-frequency gravitational waves on photonic-like electronic transport in graphene. The results show that, unlike the influence of gravitational waves on the propagation of light, the influence of gravitational waves on photonic-like electronic transport can accumulate not only in real space but also in $k$-space. This makes photonic-like electronic transport under gravitational waves similar to the propagation of light in a medium where the refractive index varies dramatically due to gravitational waves, and with shorter wavelengths. As a result, the relative intensity variation in photonic-like electronic transport under gravitational waves exceeds that of a laser interferometer with the same arm length by six orders of magnitude. At low temperatures, the influence of phonons on photon-like transport in the context of high-frequency gravitational waves can be ignored. These findings indicate a strong interaction between gravitational waves and electron transport, which helps to deepen the understanding of the interaction between gravitational waves and matter, and provides a different method for detecting high-frequency gravitational waves.

physics.ins-det↗

arXiv2023

High-sensitivity graphene MEMS force and acceleration sensor based on graphene-induced non-radiative transition

The micro-electromechanical-system (MEMS) force and acceleration sensor utilizing the graphene-induced non-radiative transition was investigated. The graphene-induced non-radiative transition is very sensitive to the distance, and the deflection of the graphene ribbon is highly susceptive to applied force or acceleration. Thus, a high-sensitivity MEMS sensor can be achieved with detecting the graphene ribbon's deflection of 1 nm, the force of 0.1 pN, and the acceleration of 0.1 mg. The MEMS sensor, with a size of only tens of microns, can be charged by light irradiation without connecting power sources. In addition, it allows long-distance detection, i.e., wireless transmitter circuit can be omitted. Therefore, it will have significant application prospects in the fields of micro-smart devices, wearable devices, biomedical systems, and so on.

cond-mat.mes-hall↗

arXiv2019

Detailed polarization measurements of the prompt emission of five Gamma-Ray Bursts

Gamma-ray bursts are the strongest explosions in the Universe since the Big Bang, believed to be produced either in forming black holes at the end of massive star evolution or merging of compact objects. Spectral and timing properties of gamma-ray bursts suggest that the observed bright gamma-rays are produced in the most relativistic jets in the Universe; however, the physical properties, especially the structure and magnetic topologies in the jets are still not well known, despite several decades of studies. It is widely believed that precise measurements of the polarization properties of gamma-ray bursts should provide crucial information on the highly relativistic jets. As a result there have been many reports of gamma-ray burst polarization measurements with diverse results, see, however many such measurements suffered from substantial uncertainties, mostly systematic. After the first successful measurements by the GAP and COSI instruments, here we report a statistically meaningful sample of precise polarization measurements, obtained with the dedicated gamma-ray burst polarimeter, POLAR onboard China's Tiangong-2 spacelab. Our results suggest that the gamma-ray emission is at most polarized at a level lower than some popular models have predicted; although our results also show intrapulse evolution of the polarization angle. This indicates that the low polarization degrees could be due to an evolving polarization angle during a gamma-ray burst.

astro-ph.HE↗

arXiv2018

Nonmonotonic strain dependence of lattice thermal conductivity in monolayer SiC: a first-principles study

An increasing number of two-dimensional (2D) materials have already been achieved experimentally or predicted theoretically, which have potential applications in nano- and opto-electronics. Various applications for electronic devices are closely related to their thermal transport properties. In this work, the strain dependence of phonon transport in monolayer SiC with a perfect planar hexagonal honeycomb structure is investigated by solving the linearized phonon Boltzmann equation. It is found that room-temperature lattice thermal conductivity ($κ_L$) of monolayer SiC is two orders of magnitude lower than that of graphene. The low $κ_L$ is due to small group velocities and short phonon lifetimes, which can also be explained by polarized covalent bond due to large charge transfer from Si to C atoms. In considered strain range, it is proved that the SiC monolayer is mechanically and dynamically stable. With increased tensile strain, the $κ_L$ of SiC monolayer shows an unusual nonmonotonic up-and-down behavior, which is due to the competition between the change of phonon group velocities and phonon lifetimes of low frequency phonon modes. At low strains ($<$8\%), the phonon lifetimes enhancement induces the increased $κ_L$, while at high strains ($>$8\%) the reduction of group velocities as well as the decrease of the phonon lifetimes are the major mechanism responsible for decreased $κ_L$. Our works further enrich studies on phonon transports of 2D materials with a perfect planar hexagonal honeycomb structure, and motivate farther experimental studies.

cond-mat.mtrl-sci↗

arXiv2017

Strain effects on phonon transport in antimonene from a first-principles study

Strain engineering is a very effective method to continuously tune the electronic, topological, optical and thermoelectric properties of materials. In this work, strain-dependent phonon transport of recently-fabricated antimonene (Sb monolayer) under biaxial strain is investigated from a combination of first-principles calculations and the linearized phonon Boltzmann equation. It is found that the ZA dispersion of antimonene with strain less than -1\% gives imaginary frequencies, which suggests that compressive strain can induce structural instability. Experimentally, it is possible to enhance structural stability by tensile strain. Calculated results show that lattice thermal conductivity increases with strain changing from -1\% to 6\%, and lattice thermal conductivity at 6\% strain is 5.6 times larger than that at -1\% strain at room temperature. It is interesting that lattice thermal conductivity is in inverse proportion to buckling parameter $h$ in considered strain range. Such a strain dependence of lattice thermal conductivity is attributed to enhanced phonon lifetimes caused by increased strain, while group velocities have a decreased effect on lattice thermal conductivity with increasing strain. It is found that acoustic branches dominate the lattice thermal conductivity over the full strain range. The cumulative room-temperature lattice thermal conductivity at -1\% strain converges to maximum with phonon mean free path (MFP) at 50 nm, while one at 6\% strain becomes as large as 44 $\mathrm{μm}$, which suggests that strain can give rise to very strong size effects on lattice thermal conductivity in antimonene. These results may provide guidance on fabrication techniques of antimonene, and offer perspectives on tuning lattice thermal conductivity by size and strain for applications of thermal management and thermoelectricity.

cond-mat.mtrl-sci↗

arXiv2017

Enhanced circular photogalvanic effect in HgTe quantum wells in the heavily inverted regime

Thanks to the strong spin-orbit interaction (SOI), HgTe-based quantum wells (QWs) exhibit very rich spin-related properties. But the full descriptions of them are beyond the simple parabolic band models and conventional Rashba and Dresselhaus SOI terms, as a result of the strong interband coupling of the narrow gap band structures. Here, we develop a theoretical method to calculate the circular photogalvanic effect (CPGE) in Hg$_{0.3}$Cd$_{0.7}$Te/HgTe/Hg$_{0.3}$Cd$_{0.7}$Te quantum wells (HgTe QWs) based on the realistic eight-band $\mathbf{k}\cdot\mathbf{p}$ model with density matrix formalism. Our method could take account of the unusual band structures and SOIs of HgTe QWs, therefore can be used to calculate the CPGE currents in HgTe QWs with non-parabolic, Dirac-like and inverted energy dispersions. The microscopic origin of CPGE and the interplay effect of structure inversion asymmetry (SIA) and bulk inversion asymmetry (BIA) is also investigated. In addition, this method is extended to study the pure spin currents (PSCs) in HgTe QWs injected by linearly polarized light at normal incidence. Our calculation results support the following findings: (i) In the inverted phase regime, the energy dispersion of heavily inverted HgTe QWs could be strongly distorted, lead to a significant enhancement of CPGE at a certain range of energy spectrum. (ii) The interplay of SIA and BIA could lead to the CPGE currents anisotropically dependent on the azimuth angle of oblique incident light. (iii) The PSC $j_{y'}^{x'}$ ($x'\parallel[110]$ and $y'\parallel[\bar{1}10]$) produced by [110]-linearly-polarized light could change sign with HgTe QW transformed from normal phase to inverted phase. These findings might be utilized in developing the HgTe-based infrared/terahertz optoelectronic and spintronic devices.

cond-mat.mes-hall↗

arXiv2016

Resonant electron-phonon-electron interaction

The effect of the resonance of electron scattering energy difference and phonon energy on the electron-phonon-electron interaction (EPEI) is studied. Results show that the resonance of electron transition energy and phonon energy can enhance EPEI by a magnitude of 1 to 2. Moreover, the anisotropic S-wave electron or dx2-y2 electron can enhance resonance EPEI, and the self-energy correction of the electron will weaken resonance EPEI. Particularly, the asymmetrical spin-flip scattering process in k space can reduce the effect of electronic self-energy to enhance resonance EPEI

cond-mat.supr-con↗

arXiv2016

Enhanced absorption of monolayer MoS2 with resonant back reflector

By extracting the permittivity of monolayer MoS2 from experiments, the optical absorption of monolayer MoS2 prepared on top of one-dimensional photonic crystal (1DPC) or metal films is investigated theoretically. The 1DPC and metal films act as resonant back reflectors that can enhance absorption of monolayer MoS2 substantially over a broad spectral range due to the Fabry-Perot cavity effect. The absorption of monolayer MoS2 can also be tuned by varying either the distance between the monolayer MoS2 and the back reflector or the thickness of the cover layers.

physics.optics↗

arXiv2015

Broadband perfect light trapping in the thinnest monolayer graphene-MoS$_{2}$ photovoltaic cell

The light absorption of a monolayer graphene-molybdenum disulfide photovoltaic (GM-PV) cell in a wedge-shaped microcavity with a spectrum-splitting structure is investigated theoretically. The GM-PV cell, which is three times thinner than the traditional photovoltaic cell, exhibits up to 98\% light absorptivity in a wide wavelength range. This rate exceeds the fundamental limit of nanophotonic light trapping in solar cells. The effects of defect layer thickness, GM-PV cell position in the microcavity, incident angle, and lens aberration on the light absorption rate of the GM-PV cell is explored. Regardless of errors, the GM-PV cell can still achieve at least 90\% light absorptivity with the current technology. Our proposal provides different methods to design light-trapping structures and apply spectrum-splitting systems.

physics.optics↗

arXiv2015

Broadband ultra-high transmission of terahertz radiation through monolayer MoS$_{2}$

In this study, terahertz (THz) absorption and transmission of monolayer MoS$_{2}$ was calculated under different carrier concentrations. Results showed that the THz absorption of monolayer MoS$_{2}$ is very small even under high carrier concentrations and large incident angle. Equivalent loss of the THz absorption is the total sum of reflection and absorption that is one to three grades lower than that of graphene. The monolayer MoS$_{2}$ transmission is much larger than that of the traditional GaAs and InAs two-dimensional electron gas. The field-effect tubular structure formed by the monolayer MoS$_{2}$-insulation-layer-graphene is investigated. In this structure the THz absorption of graphene to reach saturation under low voltage. Meantime, the maximum THz absorption of monolayer MoS$_{2}$ was limited to approximately 5\%. Thus, monolayer MoS$_{2}$ is a kind of ideal THz Transparent Electrodes.

physics.optics↗

arXiv2014

Control of absorption of monolayer MoS$_{2}$ thin-film transistor in one-dimensional defective photonic crystal

The light absorption and transmission of monolayer MoS$_{2}$ in a one-dimensional defective photonic crystal (d-1DPC) is theoretically investigated. The study shows that the strong interference effect decreases photon density in particular areas of the microcavity. The d-1DPC can reduce light absorption of monolayer MoS$_{2}$ and enhance light transmission. The impact of monolayer MoS$_{2}$ light absorption on the localization effect of photon is investigated when monolayer MoS$_{2}$ and the organic light-emitting diode are located in the same microcavity. However, monolayer MoS$_{2}$ does not reduce the localization effect of light by regulating the position of monolayer MoS$_{2}$ in the microcavity.

physics.optics↗

arXiv2014

Perfect light trapping in nanoscale thickness semiconductor films with resonant back reflector and spectrum-splitting structures

The optical absorption of nanoscale thickness semiconductor films on top of light-trapping structures based on optical interference effects combined with spectrum-splitting structures is theoretically investigated. Nearly perfect absorption over a broad spectrum range can be achieved in $<100$ nm thick films on top of one-dimensional photonic crystal or metal films. This phenomenon can be attributed to interference induced photonic localization, which enhances the absorption and reduces the reflection of the films. Perfect solar absorption and low carrier thermalization loss can be achieved when the light-trapping structures with wedge-shaped spacer layer or semiconductor films are combined with spectrum-splitting structures.

physics.optics↗

arXiv2013

Gate-tunable nearly total terahertz absorption in graphene with resonant metal back reflector

The gate-tunable terahertz (THz) absorption of graphene layers with a resonant metal back reflector (RMBF) is theoretically investigated. We demonstrate that the THz absorption of graphene with RMBF can vary from nearly negligible to nearly total by tuning the external gate voltage. This peculiar nearly total THz absorption can be attributed to the Fabry-Perot cavity effect, which enhances the absorption and reduces the reflection of graphene. The absorption spectra of the graphene-RMBF structure can also be tailored in bandwidth and center frequency by changing the thickness and dielectric constant of the spacer layer.

cond-mat.mes-hall↗