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(a) ARPES measured LaSb electronic structure. (b) Quantum oscillation experimental data. (c) The two-dimensional Fermi surface analyzed by ARPES and quantum oscillation data can be symmetrically constructed to further construct a three-dimensional Fermi surface and solve the concentration of carriers. (d) Two-band and three-band models fit the magnetoresistive data.
Magnetoresistance is the change in resistance of a material under an applied magnetic field. Magnetoresistance is not only an important research object in condensed matter physics, but also has extensive application value. Many magnetic materials exhibit significant negative magnetoresistance effects, such as giant magnetoresistance (GMR) in magnetic multilayer films and coercive magnetoresistance (CMR) in perovskite manganese oxides. The 2007 Nobel Prize in physics was awarded to Albert Fert and Peter Grunberg for their outstanding contribution to the discovery of GMR. As early as 1930, a very large positive magnetic resistance (XMR) was also found in the non-magnetic material Bi.
In 2014, no saturation XMR was observed in a magnetic field of up to 60 T in the non-magnetic half-metal WTe2, which quickly attracted widespread attention. The magnetic reluctance of WTe2 exhibits a typical near quadratic magnetic field dependence, and at high fields the resistance increases rapidly at low temperatures and then reaches saturation. These behaviors have also recently been observed in many nonmagnetic half metal TmPn2 (Tm = Ta/Nb, Pn = As/Sb), LnX (Ln = La/Y, X = Sb/Bi) and ZrSiS series. A variety of mechanisms have been proposed to explain this type of XMR. However, due to the very complex electronic structures of many non-magnetic semimetals, it is difficult to conduct in-depth quantitative analysis based on these electronic structures.
Recently, Institute of Physics, Chinese Academy of Sciences/Beijing National Laboratory for Condensed Matter Physics (Group X) Zeng Lingkun and associate researcher Qian Tian, ​​PhD candidate EX1, Wu Desheng, and researcher Yan Jianlin, Ph.D., Ph.D., Department of Physics, Renmin University of China Professor Wang Shancai and his collaborators studied the electronic structure of LaSb giant reluctance materials through angularly resolved photoelectron spectroscopy (ARPES) and quantum oscillation measurements, and analyzed the mechanism of XMR based on the experimental results.
These results include: 1) Based on the experimental data of ARPES and quantum oscillation, the shape and size of all Fermi surfaces of LaSb are solved, and it is proved that LaSb hole and electron carriers are completely compensated at low and high temperatures, excluding Magneto-resistance is significantly reduced at high temperatures due to the carrier's non-compensating interpretation; 2) By analyzing the experimental band and combining the energy band calculations, LaSb is proved to be topologically mediocre, excluding the origin of XMR from the topological non- mediocre band. Explanation; 3) Pulse field measurement of LaSb is performed. No sign of magnetoresistive saturation is observed in a magnetic field of up to 40 T. The analysis of the magnetoresistive data reveals that the magnetic reluctance dependence on the magnetic field cannot be used by the traditional two bands. The model explained; 4) Finally, based on the electronic structure of LaSb, a three-band model was constructed and the magnetoresistive data was fitted quantitatively.
The analysis of the experimental results shows that the XMR in the non-magnetic semi-metal and the related magnetic transmission operation are closely related to the electronic structure of the multi-energy band. These experiments revealed that LaSb is the simplest electronic structure of all known XMR semimetals of the same class. It is an ideal material for the study of nonmagnetic semimetal XMRs, and gives detailed results of Fermi surfaces and energy band dispersions. The model's comprehensive quantitative understanding of XMR in non-magnetic semimetals provides key experimental data.
This research was published online on September 16 in Physical Review Letters 117 (127204 (2016)). This work was supported by the Ministry of Science and Technology's "National Major Scientific Research Plan" and "National Key R&D Program," the National Natural Science Foundation of China, and the Pilot Project B of the Chinese Academy of Sciences.
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