arXiv subjects

X. F. Jiang

Publications and source records attributed to X. F. Jiang.

13 recordsLinked to original sources

arXiv2026

The role of near neutron drip-line nuclei in the $r$-process

The role of near neutron-drip-line nuclei in the rapid neutron-capture process ($r$-process) is studied with the classical $r$-process model. Simulations under different astrophysical conditions ($T$, $n_n$) show that $r$-process paths approach the neutron-drip line under low-temperature and high-neutron-density conditions. A sensitivity study reveals that variations in the nuclear masses of these exotic nuclei significantly impact the abundances of superheavy nuclei, and lead to obvious abundance variations in the $A=110-125$, $A=175-185$, and $A=200-205$ regions. By contrast, the $r$-process rare-earth peak and the $A=130,195$ peaks remain largely unaffected. The nuclei that obviously impact $r$-process abundances are mainly distributed in the region of $25\leq Z\leq 90$ and $50\leq N\leq 180$, with the nuclei around neutron magic numbers found to be particularly important for the $r$-process, even in the near-neutron-drip-line region.

nucl-th↗

arXiv2026

Dipole response in deformed halo nuclei $^{42}\mathrm{Mg}$ and $^{44}\mathrm{Mg}$

The quasiparticle finite amplitude method based on the deformed relativistic Hartree-Bogoliubov theory in continuum has been developed for the noncharge-exchange multipole response. Taking neutron-rich magnesium isotopes as examples, the isovector electric dipole response, especially in the low-lying region, is studied. It is found that the low-energy dipole strength increases with neutron number and becomes notably enhanced in the predicted deformed halo nuclei $^{42}\mathrm{Mg}$ and $^{44}\mathrm{Mg}$. In these isotopes, the $K^π=1^-$ states below 3 MeV are dominated by transitions from the ``halo" part of the single-neutron orbitals. Their transition densities reveal a low-frequency, out-of-phase oscillation between the neutron halo and the core. These results provide a microscopic picture for the soft dipole resonance in $^{42}\mathrm{Mg}$ and $^{44}\mathrm{Mg}$.

nucl-th↗

arXiv2025

Exploratory study on the masses of odd-$Z$ nuclei and $r$-process simulation based on the deformed relativistic Hartree-Bogoliubov theory in continuum

Nuclear masses of exotic nuclei are important for both nuclear physics and astrophysics. The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) is capable of providing proper descriptions for exotic nuclei by simultaneously including deformation, pairing correlation and continuum effects, and a mass table of even-$Z$ nuclei with $8 \leqslant Z \leqslant 120$ has been developed based on the DRHBc theory. This work employs a methodology to estimate the masses of odd nuclei using neighboring even nuclei's masses and microscopic pairing gaps, and the performance of microscopic pairing gaps are validated by comparing with empirical ones. Combining the DRHBc masses of even-$Z$ nuclei and the estimated masses of odd-$Z$ nuclei, a pseudo DRHBc mass table is developed, with the root-mean-square (rms) deviation from available mass data $σ=1.47$ MeV. Then this mass table is employed in the $r$-process simulation; results show that the differences in the details of pairing gaps do not yield qualitative discrepancy in $r$-process abundances, while the deformation effects can influence the $r$-process path and thus affect the $r$-process abundance. In particular, the nuclear shape transitions can even lead to the discontinuity of the $r$-process path, suggesting that incorporating triaxiality or beyond-mean-field effects would be valuable for further improvement.

nucl-th↗

arXiv2020

Anisotropic transport and quantum oscillations in the quasi-one-dimensional TaNiTe5: Evidence for the nontrivial band topology

The past decade has witnessed the burgeoning discovery of a variety of topological states of matter with distinct nontrivial band topologies. Thus far, most of materials studied possess two-dimensional or three-dimensional electronic structures, with only a few exceptions that host quasi-one-dimensional (quasi-1D) topological electronic properties. Here we present the clear-cut evidence for Dirac fermions in the quasi-1D telluride TaNiTe5. We show that its transport behaviors are highly anisotropic and we observe nontrivial Berry phases via the quantum oscillation measurements. The nontrivial band topology is further corroborated by first-principles calculations. Our results may help to guide the future quest for topological states in this new family of quasi-1D ternary chalcogenides.

cond-mat.str-el↗

arXiv2020

Magnetic-field-induced nontrivial electronic state in the Kondo-lattice semimetal CeSb

Synergic effect of electronic correlation and spin-orbit coupling is an emerging topic in topological materials. Central to this rapidly developing area are the prototypes of strongly correlated heavy-fermion systems. Recently, some Ce-based compounds are proposed to host intriguing topological nature, among which the electronic properties of CeSb are still under debate. In this paper, we report a comprehensive study combining magnetic and electronic transport measurements, and electronic band structure calculations of this compound to identify its topological nature. Quantum oscillations are clearly observed in both magnetization and magnetoresistance at high fields, from which one pocket with a nontrivial Berry phase is recognized. Angular-dependent magnetoresistance shows that this pocket is elongated in nature and corresponds to the electron pocket as observed in LaBi. Nontrivial electronic structure of CeSb is further confirmed by first-principle calculations, which arises from spin splitting in the fully polarized ferromagnetic state. These features indicate that magnetic-field can induce nontrivial topological electronic states in this prototypical Kondo semimetal.

cond-mat.mtrl-sci↗

arXiv2018

Correlation between non-Fermi-liquid behavior and superconductivity in (Ca, La)(Fe,Co)As2 iron arsenides: A high-pressure study

Non-Fermi-liquid (NFL) phenomena associated with correlation effects have been widely observed in the phase diagrams of unconventional superconducting families. Exploration of the correlation between the normal state NFL, regardless of its microscopic origins, and the superconductivity has been argued as a key to unveiling the mystery of the high-Tc pairing mechanism. Here we systematically investigate the pressure-dependent in-plane resistivity and Hall coefficient (RH ) of a high-quality 112-type Fe-based superconductor Ca1-xLaxFe1-yCoyAs2 (x = 0.2,y = 0.02). With increasing pressure, the normal-state resistivity of the studied sample exhibits a pronounced crossover from non-Fermi-liquid to Fermi-liquid behaviors. Accompanied with this crossover, Tc is gradually suppressed. In parallel, the extremum in the Hall coefficient RH (T ) curve, possibly due to anisotropic scattering induced by spin fluctuations, is also gradually suppressed. The symbiosis of NFL and superconductivity implies that these two phenomena are intimately related. Further study on the pressure-dependent upper critical field reveals that the two-band effects are also gradually weakened with increasing pressure and reduced to the one-band Werthamer-Helfand-Hohenberg limit in the low-Tc regime. Overall, our paper supports the picture that NFL, multigap, and extreme RH (T ) are all of the same magnetic origin, i.e., the spin fluctuations in the 112 iron arsenide superconductors.

cond-mat.supr-con↗

arXiv2017

Evidence of s-wave superconductivity in the noncentrosymmetric La$_7$Ir$_3$

Superconductivity in noncentrosymmetric compounds has attracted sustained interest in the last decades. Here we present a detailed study on the transport, thermodynamic properties and the band structure of the noncentrosymmetric superconductor La$_7$Ir$_3$ ($T_c$ $\sim$2.3 K) that was recently proposed to break the time-reversal symmetry. It is found that La$_7$Ir$_3$ displays a moderately large electronic heat capacity (Sommerfeld coefficient $γ_n$ $\sim$ 53.1 mJ/mol $\text{K}^2$) and a significantly enhanced Kadowaki-Woods ratio (KWR $\sim$ 32 $μΩ$ cm mol$^2$ K$^2$ J$^{-2}$) that is greater than the typical value ($\sim$ 10 $μΩ$ cm mol$^2$ K$^2$ J$^{-2}$) for strongly correlated electron systems. The upper critical field $H_{c2}$ was seen to be nicely described by the single-band Werthamer-Helfand-Hohenberg model down to very low temperatures. The hydrostatic pressure effects on the superconductivity were also investigated. The heat capacity below $T_c$ reveals a dominant s-wave gap with the magnitude close to the BCS value. The first-principles calculations yield the electron-phonon coupling constant $λ$ = 0.81 and the logarithmically averaged frequency $ω_{ln}$ = 78.5 K, resulting in a theoretical $T_c$ = 2.5 K, close to the experimental value. Our calculations suggest that the enhanced electronic heat capacity is more likely due to electron-phonon coupling, rather than the electron-electron correlation effects. Collectively, these results place severe constraints on any theory of exotic superconductivity in this system.

cond-mat.supr-con↗

arXiv2017

New approaches in agent-based modeling of complex financial systems

Agent-based modeling is a powerful simulation technique to understand the collective behavior and microscopic interaction in complex financial systems. Recently, the concept for determining the key parameters of the agent-based models from empirical data instead of setting them artificially was suggested. We first review several agent-based models and the new approaches to determine the key model parameters from historical market data. Based on the agents' behaviors with heterogenous personal preferences and interactions, these models are successful to explain the microscopic origination of the temporal and spatial correlations of the financial markets. We then present a novel paradigm combining the big-data analysis with the agent-based modeling. Specifically, from internet query and stock market data, we extract the information driving forces, and develop an agent-based model to simulate the dynamic behaviors of the complex financial systems.

q-fin.ST↗

arXiv2014

Structure of local interactions in complex financial dynamics

With the network methods and random matrix theory, we investigate the interaction structure of communities in financial markets. In particular, based on the random matrix decomposition, we clarify that the local interactions between the business sectors (subsectors) are mainly contained in the sector mode. In the sector mode, the average correlation inside the sectors is positive, while that between the sectors is negative. Further, we explore the time evolution of the interaction structure of the business sectors, and observe that the local interaction structure changes dramatically during a financial bubble or crisis.

q-fin.GN↗

arXiv2014

Spatial and temporal structures of four financial markets in Greater China

We investigate the spatial and temporal structures of four financial markets in Greater China. In particular, we uncover different characteristics of the four markets by analyzing the sector and subsector structures which are detected through the random matrix theory. Meanwhile, we observe that the Taiwan and Hongkong stock markets show a negative return-volatility correlation, i.e., the so-called leverage effect. The Shanghai and Shenzhen stock markets are more complicated. Before the year 2000, the two markets exhibit a strong positive return-volatility correlation, which is called the anti-leverage effect. After 2000, however, it gradually changes to the leverage effect. We also find that the recurrence interval distributions of both the trading volume volatilities and price volatilities follow a power law behavior, while the exponents vary among different markets.

q-fin.ST↗

arXiv2013

Time-reversal asymmetry in financial systems

We investigate the large-fluctuation dynamics in financial markets, based on the minute-to-minute and daily data of the Chinese Indices and German DAX. The dynamic relaxation both before and after the large fluctuations is characterized by a power law, and the exponents $p_\pm$ usually vary with the strength of the large fluctuations. The large-fluctuation dynamics is time-reversal symmetric at the time scale in minutes, while asymmetric at the daily time scale. Careful analysis reveals that the time-reversal asymmetry is mainly induced by external forces. It is also the external forces which drive the financial system to a non-stationary state. Different characteristics of the Chinese and German stock markets are uncovered.

q-fin.GN↗

arXiv2012

Anti-correlation and subsector structure in financial systems

With the random matrix theory, we study the spatial structure of the Chinese stock market, American stock market and global market indices. After taking into account the signs of the components in the eigenvectors of the cross-correlation matrix, we detect the subsector structure of the financial systems. The positive and negative subsectors are anti-correlated each other in the corresponding eigenmode. The subsector structure is strong in the Chinese stock market, while somewhat weaker in the American stock market and global market indices. Characteristics of the subsector structures in different markets are revealed.

q-fin.GN↗

arXiv2011

Large-volatility dynamics in financial markets

We investigate the large-volatility dynamics in financial markets, based on the minute-to-minute and daily data of the Chinese Indices and German DAX. The dynamic relaxation both before and after large volatilities is characterized by a power law, and the exponents $p_\pm$ usually vary with the strength of the large volatilities. The large-volatility dynamics is time-reversal symmetric at the time scale in minutes, while asymmetric at the daily time scale. Careful analysis reveals that the time-reversal asymmetry is mainly induced by exogenous events. It is also the exogenous events which drive the financial dynamics to a non-stationary state. Different characteristics of the Chinese and German stock markets are uncovered.

q-fin.ST↗