Tunneling Experiments of Recent Interest: Zero Bias Conductance Peak and Pseudogap Measurement

9972071 NG在这个项目中，新的和更复杂的隧道实验将在高温超导体上进行。 具体而言，零偏置电导峰值（ZBCP）和赝能隙测量将在超导体上进行。 本项目由三部分组成。 第一部分包括ZBCP在不同实验条件下的响应的研究，如1）隧穿方向，2）磁性和非磁性势垒杂质的存在下，和3）微波辐射的存在下。第二部分是对欠掺杂Bi_2Sr_2CaCu_2O_（8-d）（BSCCO）中赝能隙的测量。 将研究赝能隙对氧含量、磁场和温度的依赖性。 利用高温超导体到高温超导体的隧穿，研究了超导态中常见的倾斜特征与赝能隙之间的关系。 在项目的第三部分中，将进行两个新的实验来研究ZBCP和共同的赝能隙态。 第一个实验是在欠掺杂BSCCO中寻找当T_T_c。 如果赝能隙相中存在预形对，则Andreev反射将在隧穿电导曲线中产生弱的ZBCP。 另一种技术是使用巨磁阻（CMR）材料作为反电极。 自旋极化的电子将降低ZBCP的高度。 这些自旋极化电子也将抑制赝能隙，如果赝能隙与预形成的对在欠掺杂的高Tc超导体。 高温超导体表现出许多其他传统（普通）超导体所没有的有趣特性，这一点现在已经得到了很好的证实。普通超导体只能在非常低的温度下工作，但已经用于许多先进技术。人们正在努力改善高温超导体的性能，使其更容易、更经济地集成到技术设备中，例如长距离电力传输、储能设备、电动机等。 一个令人满意的高温超导性的基本理论还没有，这项研究是针对临界实验的性能，以帮助建立一个可接受的理论。 这项研究将涉及研究生以及本科生和博士后研究人员，他们将在当代凝聚态物理学和材料科学的前沿领域之一接受培训。 这项培训将为他们在21世纪的技术工作队伍中从事生产性职业做好准备。

9972071NgIn this project new and more sophisticated tunneling experiments will be performed on high-Tc superconductors. Specifically, Zero Bias Conductance Peak (ZBCP) and pseudogap measurements will be performed on superconductors. This project consists of three parts. The first part consists of the study of the response of ZBCP under different experimental conditions such as 1) the tunneling direction, 2) the presence of both magnetic and non-magnetic barrier impurities, and 3) the presence of microwave radiation. The second part involves careful measurements on the pseudogap found in underdoped Bi2Sr2CaCu2O8-d (BSCCO). The dependence of the pseudogap on the oxygen content, magnetic field, and the temperature will be investigated. The relationship between the dip feature commonly observed in the superconducting state and the pseudogap will also be investigated by means of high Tc superconductor - to - high Tc superconductor tunneling. In the third part of the project, two new experiments will be performed to study the ZBCP and also the pseudogap state in common. The first experiment is to search for the occurrence of Andreev reflection in underdoped BSCCO when T Tc. If there are pre-form pairs in the pseudogap phase, then Andreev reflection will produce a weak ZBCP in the tunneling conductance curve. The other technique is to use colossal magnetoresistance (CMR) material as a counter electrode. The spin polarized electrons will depress the height of ZBCP. These spin-polarized electrons will also suppress the pseudogap if the pseudogap is related to the pair pre-formation in underdoped high Tc superconductors. %%%It is now well established that high-temperature superconductors demonstrate many interesting properties that do not appear in other conventional (ordinary) superconductors. Ordinary superconductors operate at only very low temperatures yet are already used in many advanced technologies. There is a great effort underway to improve the behavior of high-temperature superconductors to allow them to be more easily and more economically integrated into technological devices, such as the transmission of electrical power over long distances, energy storage devices, electric motors, etc. These applications do depend, however, on a better understanding of high-temperature superconductivity. A satisfactory fundamental theory of high-temperature superconductivity is not yet available and this research is directed to the performance of critical experiments to assist in the establishment of an acceptable theory. This research will involve graduate as well as undergraduate students and postdoctoral research associates who will thereby receive training in one of the forefront areas of contemporary condensed-matter physics and materials science. This training will prepare them for productive careers in the technological work force during the 21st Century.