Angular dependence of SdH oscillations and reconstructed Fermi-surface of pyrite-type PtBi2
(Phys. Rev. B 98.085137 (2018))
Background
Recently, large nonsaturating magnetoresistance has been observed in various materials and electron-hole compensation has been regarded as one of the main mechanisms. Pyrite-type PtBi2, a theoretical predicted Dirac semimetal, was revealed with extremely large magnetoresistance up to 1.12×107% at low temperature at 33 T. However, its detailed Fermi surface is still lacking.
What we discover?
Here we present a detailed study of the angle-dependent Shubnikov–de Haas effect on large magnetoresistance material pyrite-type PtBi2. We reconstruct its Fermi-surface structure depend on the experiment result and extract the physical properties of each pocket. We find its Fermi surface contains four types of pockets in the Brillouin zone: three ellipsoid-like hole pockets α with C4 symmetry located on the edges (M points), one intricate electron pocket β merged from four ellipsoids along [111] located on the corners (R points), and two smooth and cambered octahedrons γ (electron) and δ (hole) on the center (Γ point). The deduced carrier densities of electrons and holes from the volume of pockets prove carrier compensation. We conclude that the compensation is the main mechanism for the large nonsaturating magnetoresistance in pyrite-type PtBi2.
The MR curves collected at T=1.7K with magnetic field parallel to the [001] direction and current direction along [100]
(Phys. Rev. B 98.085137 (2018))
Furthermore, the sub-quadratic dependence magnetoresistance grows up to 15,500,000% at the magnetic field of 80T without any sign of saturation. This is probably due to field-dependent mobilities, another feature of semimetals under high magnetic fields.
Why is this important?
We have experimentally mapped out the Fermi surface of pyrite-type PtBi2 including two hole and two electron pockets by angle dependence of SdH measurements. This allows us to deduce the carrier density and mobility of each pocket and to reveal a compensation between the electron and hole. Such compensation is further supported by two-band fitting from the temperature dependence of magnetoresistance and Hall resistivity. We ascribed the large nonsaturating magnetoresistance found in this material to the compensation. The high hole mobility may be due to the light mass and anisotropy of α pockets.
Who did the research?
Lingxiao Zhao, Liangcai Xu, Huakun Zuo, Xuming Wu, Guoying Gao, and Zengwei Zhu
Wuhan National High Magnetic Field Center School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
Funding:
This work is supported by the 1000 Youth Talents Plan, the National Science Foundation of China (Grants No. 11574097 and No. 51861135104), the National Key Research and Development Program of China (Grant No. 2016YFA0401704), and the China Postdoctoral Science Foundation (2018M630846).
