arXiv subjects

X. Lei

Publications and source records attributed to X. Lei.

6 recordsLinked to original sources

arXiv2023

Multimodality of $^{187}$Ir fission studied by Langevin approach

[Background] The fission mechanism of sub-lead nuclides remains unclear, especially the types of fission modes involved and their corresponding shell effects. [Purpose] The aim is to identify the different modes in the fission of $^{187}$Ir, and investigate the corresponding mechanism. [Method] The three-dimensional Langevin approach considering nucleus elongation, deformation, and mass asymmetry is applied to simulate fission dynamics. The macro-microscopic models are used to calculate the transport coefficients. [Results] The fragment mass, deformation, and total kinetic energy (TKE) of $^{187}$Ir fission at different excitation energies are calculated. Based on the mass-TKE correlations, four fission modes are identified, namely two asymmetric standard modes, a symmetric super-long mode, and a symmetric liquid-drop mode. Strong excitation-energy resistance of two asymmetric modes is found. The mass distributions show the dominance of single-peak shape, which is in good agreement with experimental data. The fission potential energy surface and the fission dynamics are analyzed to investigate the origins of the modes and the competition between neutron and proton shell effects. [Conclusions] Multiple fission modes are included in the $^{187}$Ir fission behind the single-peak-like distribution of observables. The proton and neutron magic numbers with different asymmetry parameter might heighten the sensitivity to the uncertainties of shell corrections.

nucl-th↗

arXiv2021

Magnetically tunable Shubnikov-de Hass oscillations in MnBi2Te4

Shubnikov-de Hass oscillations are directly observed in undoped antiferromagnetic topological insulator MnBi2Te4. With increasing magnetic fields, the oscillation period decreases gradually in the magnetic transition from canted antiferromagnetism to ferromagnetism and then saturates in high magnetic fields, indicating the field-induced evolution of the band structure. From the analysis of the high-field oscillations, a nontrivial Berry phase and a small effective mass are extracted, in agreement with the predicted Weyl semimetal phase in ferromagnetic MnBi2Te4. Furthermore, rotating the magnetization of MnBi2Te4 can lead to a splitting of the high-field oscillations, which suggests the enhanced asymmetry of the Weyl cones in tilted fields. Therefore, the observation of these magnetically tunable quantum oscillations clearly demonstrates the indispensable role of field in tuning the band structure or physical properties of MnBi2Te4.

cond-mat.mtrl-sci↗

arXiv2021

The GoogLeNet-assisted phase transition detectors

In the presence of the phase fluctuations in superconducting nanowires array, the electrical resistance of the superconducting nanowires is always non-zero unless the system undergoes Berezinskii-Kosterlitz-Thouless (BKT) transition where the superconducting vortices and anti-vortices form pairs. The two-dimensional XY model can mimic the superconducting transition temperature Tc and the BKT transition at a lower critical temperature TBKT by observing the heat capacity anomalies upon cooling. If the Josephson coupling across the nanowires is strong, the heat capacity anomalies almost overlap with each other so that it is difficult to distinguish between the Tc and the TBKT. To solve this issue, we apply an artificial-intelligence technique to split the nearly overlapped heat capacity anomalies. After the GoogLeNet-assisted phase transition detector is built, the GoogLeNet model can learn from the features of the phase transitions and then interpret the Tc and TBKT in the unseen system precisely. Our work opens a path for the GoogLeNet model to enter the world of magnetism and superconductivity.

cond-mat.supr-con↗

arXiv2020

Surface-induced linear magnetoresistance in antiferromagnetic topological insulator MnBi2Te4

Through a thorough magneto-transport study of antiferromagnetic topological insulator MnBi2Te4 (MBT) thick films, a positive linear magnetoresistance (LMR) with a two-dimensional (2D) character is found in high perpendicular magnetic fields and temperatures up to at least 260 K. The nonlinear Hall effect further reveals the existence of high-mobility surface states in addition to the bulk states in MBT. We ascribe the 2D LMR to the high-mobility surface states of MBT, thus unveiling a transport signature of surface states in thick MBT films. A suppression of LMR near the Neel temperature of MBT is also noticed, which might suggest the gap opening of surface states due to the paramagnetic-antiferromagnetic phase transition of MBT. Besides these, the failure of the disorder and quantum LMR model in explaining the observed LMR indicates new physics must be invoked to understand this phenomenon.

cond-mat.mtrl-sci↗

arXiv2019

Anisotropic Landau level splitting and Lifshitz transition induced magnetoresistance enhancement in ZrTe5 crystals

Magneto-transport study has been performed in ZrTe5 single crystals. The observed Shubnikov-de Hass quantum oscillation at low temperature clearly demonstrates the existence of a nontrivial band with small effective mass in ZrTe5. Furthermore, we also revealed the 3D anisotropic nature of high-field Landau level splitting in ZrTe5, very different from the 2D behavior measured in previous transport studies. Besides these, an abnormal large enhancement of magnetoresistance appears at high temperatures, which is believed to arise from the Lifshitz transition induced two-carrier transport in ZrTe5. Our study provides more understanding of the physical properties of ZrTe5 and sheds light on potential application of ZrTe5 in spintronics.

cond-mat.mtrl-sci↗

arXiv2017

Islands in the Gap: Intertwined Transport and Localization in Structurally Complex Materials

Localized waves in disordered one-dimensional materials have been studied for decades, including white-noise and correlated disorder, as well as quasi-periodic disorder. How these wave phenomena relate to those in crystalline (periodic ordered) materials---arguably the better understood setting---has been a mystery ever since Anderson discovered disorder-induced localization. Nonetheless, together these revolutionized materials science and technology and led to new physics far beyond the solid state. We introduce a broad family of structurally complex materials---chaotic crystals---that interpolate between these organizational extremes---systematically spanning periodic structures and random disorder. Within the family one can tune the degree of disorder to sweep through an intermediate structurally disordered region between two periodic lattices. This reveals new transport and localization phenomena reflected in a rich array of energy-dependent localization degree and density of states. In particular, strong localization is observed even with a very low degree of disorder. Moreover, markedly enhanced localization and delocalization coexist in a very narrow range of energies. Most notably, beyond the simply smoothed bands found in previous disorder studies, islands of transport emerge in band gaps and sharp band boundaries persist in the presence of substantial disorder. Finally, the family of materials comes with rather direct specifications of how to assemble the requisite material organizations.

cond-mat.mtrl-sci↗