The interplay among topology, crystal symmetry, magnetic order, and strong electron correlation can give rise to a plethora of exotic physical phenomena. The ZrSiS family is known as typical topological Dirac semimeta...
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The interplay among topology, crystal symmetry, magnetic order, and strong electron correlation can give rise to a plethora of exotic physical phenomena. The ZrSiS family is known as typical topological Dirac semimetals, among them LnSbTe (Ln denotes lanthanide) compounds exhibit intriguing characteristics due to the presence of Ln 4f electrons, resulting in quantum states and unique properties. In this paper, the topological electronic structure of PrSbTe is systematically studied by angle-resolved photoemission spectroscopy (ARPES), combined with magnetic, specific heat measurements, and band structure calculations. The detailed three-dimensional electronic structure of PrSbTe has been obtained, and a diamond-shaped Fermi surface and multiple Dirac nodal lines have been observed, which are in remarkable agreement with theoretical calculations. Moreover, the 4f electrons in PrSbTe are rather localized, which can be revealed by on-resonant ARPES data and further confirmed by the rather small Sommerfeld coefficient of γ=2.6231mJ/molK2. Our results provide more detailed information about the LnSbTe family, which gives a deeper understanding of the interaction between Ln 4f electrons and the topological states.
Several sets of energetic particle diagnostics, including a set of neutron flux monitoring systems, a solid-state neutral particle analyzer and a fast ion loss probe (FILP), have been used to investigate the energetic...
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Several sets of energetic particle diagnostics, including a set of neutron flux monitoring systems, a solid-state neutral particle analyzer and a fast ion loss probe (FILP), have been used to investigate the energetic ion losses induced by the long-lived saturated internal mode (LLM) in the HL-2A tokamak. Clear experimental evidence for different levels of energetic ion losses induced by LLM, sawtooth and minor disruption has been observed. A numerical calculation for the evolution of neutron emissions was carried out with the FBURN code, and it shows that the neutron emission drop rate linearly increases with the LLM amplitude and no threshold perturbation amplitude exists, illustrating that the loss mechanism for LLM induced energetic ion loss is dominantly convective. In addition, measurement results of the FILP demonstrate that LLM tends to expel energetic ions with relatively low energy (E < 27 keV) and high pitch angle (? > 60(?)), and can suppress the prompt loss of energetic ions with high energy and low pitch angle to a certain degree. Furthermore, the physical process for LLM induced energetic ion loss can be explained by orbit calculations, which show that LLM induced lost energetic ions will transport from center to peripheral region first, and then get lost out of plasma. The experimental observations are successfully reproduced by calculations using the ORBIT code combined with both the NUBEAM code and the MARS-K code. The paper clearly describes the whole physical process of LLM induced energetic ion loss for the first time in the HL-2A tokamak.
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