电子游戏正规平台ers have discovered a “layer” Hall effect in a solid state chip constructed of antiferromagnetic manganese bismuth telluride, a finding that signals a much sought-after topological Axion insulating state, 这个团队 报道 在杂志上 自然.
电子游戏正规平台ers have been trying to find evidence of a topological Axion insulating (TAI) state and developed some candidate materials based on theoretical calculations. The layered Hall effect represents the first clear experimental evidence of the state, 一个受量子物理定律约束的特征, according to 电子游戏软件 物理学助理教授马琼, 该项目的高级电子游戏正规平台员, 其中包括来自美国大学的36名科学家.S.美国、日本、中国、台湾、德国和印度.
物理学助理教授马琼
电子游戏正规平台人员认为，当它被完全理解时, TAI can be used to make semiconductors with potential applications in electronic devices, 马说. The highly unusual properties of Axions will support a new electromagnetic response called the topological magneto-electric effect, 为实现超灵敏铺平了道路, 超快的, 无耗散传感器, 探测器, 以及存储设备.
At the center of this line of inquiry among physicists and materials scientists are Axions, weakly-interacting particles first postulated by theorists more than 30 years ago, 马说. 它们是暗物质的主要候选者之一, a mysterious form of matter thought to account for approximately 85 percent of the universe.
While the search for Axions in high-energy physics is actively on-going, it has been recently proposed that Axions can be realized as quasi-particles in solid state materials. The prime candidate as the place to locate Axions is in a quantum TAI material, where researchers suggest Axions exist as low-energy electronic excitations, 马说.
“We set out to search for the topological Axion insulating state in a carefully designed quantum device made of even-number-layered MnBi2Te4—or manganese bismuth telluride,马说. “之前的电子游戏正规平台已经证明了这种绝缘状态, 即, 非常大的阻力, 这是, 然而, 对任何绝缘体都成立. We wanted to further demonstrate properties that are unique to Axion insulators and do not exist in regular insulators, 比如钻石.”
The material forms a two-dimensional layered crystal structure, which allowed Ma and her colleagues to mechanically exfoliate atom-thick flakes using cellophane tape that can be found in most drug stores and supermarkets. Thin flake structures with even numbers of layers were proposed to be an Axion insulator.
Ma worked closely with fellow 电子游戏软件 physicists Brian Zhou and Kenneth Burch. Zhou used a unique quantum technique to detect the magnetism of MnBi2Te4. Burch has a unique glovebox facility used to process the sample in an inert environment.
“We first characterized the layer number with optical methods and then performed electrical transport measurements, such as measuring the sample resistance under different conditions, 包括变电场, 磁场, 环境温度,马说.
电子游戏正规平台人员发现了霍尔效应, a well known law of physics where electrons travel at an angle from the axis under the influence of an applied 磁场. Only these electrons were traveling without such assistance, 马说. 关键在于材料的拓扑结构, or the quantum characteristics of its electrons and the waves in which they function.
“We observed a novel property for electrons travelling across this material in its Axion insulating state: The electrons do not travel in a straight line; instead, 它们向横向偏转. This effect was usually only observed under a large 磁场, 这就是霍尔效应,马说. “但是这里, the deflection occurs due to inherent topology of the materials and without external 磁场. More interestingly, the electrons deflect to opposite sides on the top and bottom layers. 因此，我们将其命名为霍尔效应. The layer Hall effect serves as a distinct signature of the topological Axion insulating state, 这在常规绝缘体中不会发生.”
马对这个项目的电子游戏正规平台得到了美国农业部的支持.S. 能源部, said 这个团队 was surprised to find that the topological Axion insulating state and the layer Hall effect can be effectively controlled by the so-called Axion field, 这是 the product of applying both an electric field and a 磁场.
“This means that whether the electrons deflect to the left or to the right on the top and bottom layers can be switched by the collective application of the electrical and 磁场s,马说. “A single field is not able to switch one situation to the other.”
Harvard University Assistant Professor of Chemistry Suyang Xu, 该报告的主要作者, 添加, “We are very excited about this work because it demonstrates the first realistic platform for the topological Axion insulator state.”
马说 the identification of the topological Axion insulating state leads to the next step of searching for signatures of the defining Axion dynamics in this system, 这被称为拓扑磁电效应.
“The topological ME effect is a fundamentally new mechanism to convert electricity to magnetism, 反之亦然, 没有能量损失, and has great potential to realize ultra-energy-efficient spintronic 以及存储设备,马说。.
To demonstrate such will require further optimization of the material quality, 设备的几何形状, 扩大实验能力, 马说.
Ed Hayward |大学传播| 2021年8月