Scanning tunneling microscopy studies on Andreev reflection and pseudogap in high-T_c cuprate superconductors

高温铜酸盐超导体中Andreev反射和赝能隙的扫描隧道显微镜研究

基本信息

批准号：
12640327
负责人：
ODA Migaku
金额：
$ 2.75万
依托单位：
HOKKAIDO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

In the present study, we have performed tunneling spectroscopy and Andreev reflection experiments using scanning tunneling microscope (STM), and obtained the following results.1) In tunneling spectroscopy experiments, it has been found that in the lectronic excitations, there exist two kinds of pseudogaps (LPG and SPG) ; one with a characteristic energy comparable to the superconducting (SC) gap Δ and another one that is 3 to 4 times larger.2) The larger energy-scale pseudogap (LPG) develops progressively below higher crossover temperature T_<max>. On the other hand, the smaller energy-scale pseudogap (SPG) develops progressively below lower crossover temperature T* in addition to the LPG, and evolves smoothly into the SC gap below T_c. The SC gap amplitude Δ scales with T* in the entire carrier (hole) concentration region examined.3) In Andreev reflection experiments, it has been suggested that the Andreev gap, which has been considered to reflect the effective energy gapΔ_<eff>^ due to coherent pairing, scales with T_c.The above findings, combined with the results in angle-resolved photoemission experiments on the pseudogap evolution in the k-space, suggest that an energy gap around the so-called "cold spots", which opens below T_c, functions as the effective energy gap Δ_<eff>, and the carriers around me cold spots play an crucial role in establishing the long-range phase coherence in the collective motion of pairs.

在演讲研究中，我们使用扫描隧道显微镜（STM）进行了隧道光谱和Andreev反射实验，并获得了以下结果。1）在隧道光谱实验中，已经发现，在胶质激励中，存在两种PSEUDOGAPP（LPG和SPG和SPG和SPG）；一个具有与超导（SC）GAPδ相当的特征能量，另一个具有3至4倍大的能量。2）较大的能量尺度伪PSEUDOGAP（LPG）逐渐低于较高的交叉温度T_ <max>。另一方面，除了LPG之外，较小的能量尺度伪PSEUDOGAP（SPG）在较低的交叉温度t*以下逐渐发展，并顺利演变为T_C以下的SC间隙。 SC间隙放大器δδ在检查的整个载体（孔）浓度区域中与T*缩放。3）在Andreev反射实验中，已经提出，已考虑将Andreev GAP与T_C的相干配对，与Pseion coptions consections consection consection consement consement consement consement-reys crounede consecy-resy Reselection相结合，该差距被认为反映了有效的能量gapΔ__<eff>^在k空间中，表明所谓的“冷点”围绕T_C以下打开的能量隙可以充当有效的能隙Δ_<eff>，而我周围的载体在对成对的集体运动中建立远距离相干性方面起着至关重要的作用。