A Low Temperature Investigation of Amorphous Materials

非晶态固体的低温性能是显著的 不同于众所周知的结晶行为， 材料. 在低于1K的温度下，这种差异是由 局部激发 不知道是什么激发 对于任何无定形固体，但它们似乎来自于 具有原子大小的实体的隧穿运动。 的目的 拟议的研究是为了进一步确立 局部激发在超导低温性能， 确定如何操纵或控制激励，以及 最终确定在某些非晶激发 系统. 在较高的温度下，比热和 玻璃状固体的热导率再次显示出不寻常的 晶体中通常没有的行为。 拟议研究 也将试图建立一个定性的解释， 这些特征。 实验方法包括测量 比热、导热率、热膨胀，以及 硅酸盐样品的超声和介电分散 玻璃、无定形聚合物和取向无序 作为每个样品的无序基质的固体被修改 系统地

The low-temperature properties of amorphous solids are remarkably different from the well-understood behavior of crystalline materials. At temperatures below 1K this difference is caused by localized excitations. It is not known what the excitations are for any amorphous solid, but they appear to arise from the tunneling motion of some entity having atomic size. A purpose of the proposed research is to further establish the role of the localized excitations in seveal low-temperature properties, to determine how to manipulate or control the excitations, and eventually to identify the excitations in certain amorphous systems. At higher temperatures, both the specific heat and thermal conductivity of glassy solids again exhibit unusual behavior normally not found in a crystal. The proposed research will also attempt to establish a qualitative explanation for these features. The experimental approach involves measurements of specific heat, thermal conductivity, thermal expansion, and ultrasonic and dielectric dispersion on samples of silicate glasses, amorphous polymers, and orientationally disordered solids as the disordered matrix of each sample is modified systematically.