Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843-4242;
Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
Proc Natl Acad Sci U S A. 2018 Jul 3;115(27):6995-6999. doi: 10.1073/pnas.1721493115. Epub 2018 Jun 18.
A phase transition occurs when correlated regions of a new phase grow to span the system and the fluctuations within the correlated regions become long lived. Here, we present neutron scattering measurements showing that this conventional picture must be replaced in YFeAl, a compound that forms naturally very close to a [Formula: see text] quantum phase transition. Fully quantum mechanical fluctuations of localized moments are found to diverge at low energies and temperatures; however, the fluctuating moments are entirely without spatial correlations. Zero temperature order in YFeAl is achieved by an entirely local type of quantum phase transition that may originate with the creation of the moments themselves.
当新相的关联区域生长到跨越整个系统，并且关联区域内的涨落变得持久时，就会发生相变。在这里，我们呈现了中子散射测量结果，表明在 YFeAl 中，这种传统的图景必须被取代，YFeAl 是一种在[Formula: see text]量子相变附近自然形成的化合物。在低能量和温度下，局域矩的全量子力学涨落被发现是发散的；然而，涨落的矩完全没有空间相关性。YFeAl 的零温有序是通过一种完全局域的量子相变实现的，这种相变可能源于矩本身的产生。
