Development of a Submillimeter Spectrometer Operating at He-3 Temperatures

9704299 Basov该合同用于开发在He-3温度下工作的亚毫米光谱仪，用于研究新材料的基本特性。红外光谱和光谱学的实验方法在凝聚态科学中是非常有用的。然而，通常这些方法不允许在低于30-50 cm-1的频率和低于6-12 K的温度下进行测量。这些共同限制的一个直接后果是，在常规光谱学技术的范围之外，存在着广阔的未开发的新材料现象领域。对这些现象进行实验研究的仪器先决条件包括能够达到低至2-3 cm-1的频率，同时保持样品在T降至0.3 K。开发符合上述严格要求的设施是本提案的主要目标。最初的研究项目将致力于凝聚态物理的前沿问题之一，即金属间化合物中的非常规导电性和超导性。金属间材料的奇特输运性质提出了挑战金属理论基础的基本问题。目前，加州大学圣地亚哥分校物理系的几个小组正在研究具有强相关电子的金属间系统。该光谱计划将通过扩展红外区域的测量，极大地丰富联合研究能力，在红外区域，由于相互作用和相关性的影响主导了这些相关系统的响应。在这个项目中描述的红外设备将提供发射实验的手段，这在以前是不可能的，因为仪器的限制。特别是，超导态电动力学尚未在重费米子、有机材料或硼碳化物中进行探索。深入研究上述化合物的红外响应是初始研究计划的主要目标之一。另一个方向是Nd2-yCeyCuO4，它是一种电子型铜超导体。与所有其他铜酸盐不同，这种特殊材料与传统的BCS超导体有某些相似之处。另一方面，输运实验表明，该系统揭示了重的类似费米子的低能激发。这种材料有争议的性质可以通过在超导状态下对其电磁响应的调查来澄清。最后，将进行（Y-Pr）Ba2Cu3O7-x中超导体-绝缘体跃迁（SIT）和赝隙的光谱研究实验。期望对合成金属中超导态和SIT物理的详细研究将增进我们对非常规超导性和高度相关电子的一般行为的理解。＊＊＊

9704299 Basov This award is provided to develop a submillimeter spectrometer operating at He-3 temperatures for the studies of fundamental properties of novel materials. Experimental methods of infrared and optical spectroscopy are extremely informative in condensed matter science. However, usually these methods do not permit to perform measurements at frequencies below 30-50 cm-1 and at temperatures below 6-12 K. An immediate consequence of these common restrictions is the existence of a vast unexplored territory of new materials phenomena which lie beyond the scope of routine spectroscopic techniques. Instrumental prerequisites for the experimental study of these phenomena include the ability to reach frequencies as low as 2-3 cm-1 while keeping the specimens at T down to 0.3 K. Development of the facility that meets the above stringent requirements is the primary goal of this proposal. The initial research project will be devoted to one of the forefront problems of condensed matter physics which is Unconventional Conductivity and Superconductivity in Intermetallic Compounds. The exotic transport properties of intermetallic materials pose fundamental questions which challenge the foundation of the theory of metals. Currently several groups at the UCSD physics department are involved in the study of intermetallic systems with strongly correlated electrons. This spectroscopic program will greatly enrich the joint research capabilities by extending measurements in the infrared region where the effects due to interactions and correlations dominate the response of these correlated systems. An infrared facility described in this project will provide the means to launch experiments which were previously impossible because of instrumental limitations. In particular, super-conducting state electrodynamics has not been explored in heavy fermions, in organic materials or in borocarbides. A thorough study of the infrared response of the above compound s is one the primary targets of the initial research program. Another direction will be concerned with Nd2-yCeyCuO4 which is an electron-type cuprate superconductor. Unlike all other cuprates this specific materials shows certain similarities with conventional BCS superconductors. On the other hand, transport experiments indicate that this system reveals heavy fermion-like low-energy excitations. The controversial nature of this material may be clarified through a survey of its electro-magnetic response in the superconducting state. Finally, experiments aimed at the spectroscopic study of the superconductor-insulator transition (SIT) and of a pseudogap in (Y-Pr)Ba2Cu3O7-x will be performed. %%% It is expected that the detailed investigation of superconducting state in synthetic metals and of the SIT physics will enhance our understanding of unconventional superconductivity and of general behavior of highly correlated electrons. ***