Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China.
MS-E536, NHMFL, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Nat Commun. 2017 May 19;8:15297. doi: 10.1038/ncomms15297.
The Fermi surface of elemental bismuth consists of three small rotationally equivalent electron pockets, offering a valley degree of freedom to charge carriers. A relatively small magnetic field can confine electrons to their lowest Landau level. This is the quantum limit attained in other dilute metals upon application of sufficiently strong magnetic field. Here we report on the observation of another threshold magnetic field never encountered before in any other solid. Above this field, B, one or two valleys become totally empty. Drying up a Fermi sea by magnetic field in the Brillouin zone leads to a manyfold enhancement in electric conductance. We trace the origin of the large drop in magnetoresistance across B to transfer of carriers between valleys with highly anisotropic mobilities. The non-interacting picture of electrons with field-dependent mobility explains most results but the Coulomb interaction may play a role in shaping the fine details.
元素铋的费米表面由三个小的旋转等价电子口袋组成，为载流子提供了一个谷自由度。相对较小的磁场可以将电子限制在其最低的朗道能级。这是在其他稀金属中施加足够强的磁场后达到的量子限制。在这里，我们报告了在任何其他固体中从未遇到过的另一个阈值磁场的观察结果。在此场强 B 之上，一个或两个谷完全为空。通过在布里渊区中的磁场使费米海干涸会导致电导率大大增强。我们追踪了磁阻在 B 处大幅下降的起源，发现载流子在各向异性迁移率的谷之间转移。具有场依赖迁移率的电子的非相互作用图像可以解释大多数结果，但库仑相互作用可能在形成精细细节方面发挥作用。
