论文标题
半金属到半导体转变的电子起源和尖晶石HGCR2SE4中的巨大磁性
Electronic Origin of Half-metal to Semiconductor Transition and Colossal Magnetoresistance in Spinel HgCr2Se4
论文作者
论文摘要
半米是托有自旋偏置的导载体的铁磁体，对于旋转型应用至关重要。 Chromium尖晶石HGCR2SE4代表了一种独特的半米类型，该类型具有半米至半导体转变（HMST），并在铁磁 - 磁性（FM-PM）转变上表现出巨大的磁倍率（CMR）。使用角度分辨光发射光谱（ARPES），我们发现N型HGCR2SE4（N-HGCR2SE4）的费米表面由一个单个电子袋组成，该袋在FMI级别（EF）上移动到FMI级别（EF），而FMI级别（EF）在FM-PM转换上移动，并通往HMST。这样的Lifshitz过渡表现出了一个巨大的带拆分，该带源自与特定化学非化学计量法揭示的交换相互作用。交换带拆分和化学非化学计量学是HMST和CMR的两种关键成分，与我们的AB-Initio计算一致。我们的发现提供了HGCR2SE4异常特性的电子起源的光谱证据，该特性解决了半米中独特的相变。
Half-metals are ferromagnets hosting spin-polarized conducting carriers and crucial for spintronics applications. The chromium spinel HgCr2Se4 represents a unique type of half-metal, which features a half-metal to semiconductor transition (HMST) and exhibits colossal magnetoresistance (CMR) across the ferromagnetic-paramagnetic (FM-PM) transition. Using angle-resolved photoemission spectroscopy (ARPES), we find that the Fermi surface of n-type HgCr2Se4 (n-HgCr2Se4) consists of a single electron pocket which moves above the Fermi level (EF) upon the FM-PM transition, leading to the HMST. Such a Lifshitz transition manifests a giant band splitting which originates from the exchange interaction unveiled with a specific chemical nonstoichiometry. The exchange band splitting and the chemical nonstoichiometry are two key ingredients to the HMST and CMR, consistent with our ab-initio calculation. Our findings provide spectroscopic evidences of the electronic origin of the anomalous properties of HgCr2Se4, which address the unique phase transition in half-metals.
