Condensed Matter Research using Intense Spallation Neutrons

日英中子散射合作是日本高能物理国家实验室（KEK）和英国科学与工程研究委员会（SERC）于1986年建立的一项协议的结果，该协议旨在促进日本和英国科学家在脉冲中子散射领域的科学合作和交流。它导致了ISIS设施MARI光谱仪的建设，并正式进入了科学计划日本科学家的ISIS。1994年日英合作的科学成果如下：在高tc超导体及相关材料领域的重点工作包括对高tc铜酸盐La_<1.85>Sr_<0.15>CuO_4的动态结构因子S （Q,epsilon）的MARI测量。这些实验揭示了与YBa_2Cu_3O_7不同的异常高能磁波动，最高可达300 meV。研究了S=3/2的一维Heisenberg反铁磁体CsVCl_3的量子效应。利用MARI，他们能够确定磁激发的完全色散，区域边界能量为75兆电子伏。这些测量的关键结果之一是，在区域中心没有像在整数自旋情况中发现的间隙。氢在许多固体材料的性质中起着基本的作用。中子可以获得有关其在结构中的位置及其动力学行为的信息。量子理论对于解释后者是必要的，并且使散射强度能够根据氢原子所处的势阱来解释。这可以通过测量氢波函数的形状来实现。研究了氢键在KHCO_3铁电相变中的作用，并通过S （Q,epsilon）的测量研究了晶体电位的形状。

The Japan-UK Collaboration in Neutron Scattering is a consequence of an Agreement between the Japanese National Laboratory for High Energy Physics (KEK) and UK Science and Engineering Research Council (SERC) established in 1986 to promote scientific collaboration and interchange between Japanese and UK scientists in the field of pulsed neutron scattering It has resulted in the construction of the MARI spectrometer at the ISIS Facility and has given formal accsess to the scientific program at ISIS for Japanese scientists.The scientific achievements of the Japan-UK Collaboration in the year of 1994 are as follows.Highlights of the work in the area of high-Tc superconductors and related materials include the measurements on MARI of the dynamical structure factor S (Q,epsilon) of examples of the high-Tc cuprates, La_<1.85>Sr_<0.15>CuO_4. These experiments revealed anomalous high-energy magnetic fluctuations extending up to 300 meV which are quite different from YBa_2Cu_3O_7.Quantum effects on one-dimensional Heisenberg antiferromagnet with S=3/2, CsVCl_3, were investigated. Using MARI they were able to determine the full dispersion of the magnetic excitations, with zone boundary energies of 75 meV.One of the key results of these measurements is that there is nogap at the zone center as was found in the integer spin case.Hydrogen plays a fundamental role in the properties of many solid materials. Neutrons can gain information on its position in the structure and its dynamical behavior. Quantum theory is necessary to account for the latter, and enables the scattering intensity to be interpreted in terms of the potential well in which the hydrogen atom resides. This may be accomplished by measuring the shape of the hydrogen wave function. The role of the hydrogen bond in the ferroelectric phase transition was studied in KHCO_3, and the shape of the crystal potential was studied by measuring S (Q,epsilon).