论文标题
钛酸腹膜中的介观隧道
Mesoscopic tunneling in strontium titanate
论文作者
论文摘要
原子之间的空间相关性可以在声音子的能量分散体中产生耗竭。两个众所周知的例子是超流体氦中的旋转子和金属中的科恩异常。在这里，我们通过无弹性中子散射在量子隐形SRTIO $ _3 $中观察到横向声学模式的大量软化。与其他已知情况相反，这种软化发生在微小的波矢量中，暗示空间相关性在距离上延伸到40个晶格参数。我们将其归因于由于局部应变和量子铁电波的耦合而导致的介观波动结构域的形成。因此，绝缘Srtio $ _3 $的基础状态的标志是杂交光学声子的出现。介质波动结构域在量子隧道中起作用，这阻碍了有限的宏观极化的出现。
Spatial correlation between atoms can generate a depletion in the energy dispersion of acoustic phonons. Two well known examples are rotons in superfluid helium and the Kohn anomaly in metals. Here we report on the observation of a large softening of the transverse acoustic mode in quantum paraelectric SrTiO$_3$ by means of inelastic neutron scattering. In contrast to other known cases, this softening occurs at a tiny wave vector implying spatial correlation extending over a distance as long as 40 lattice parameters. We attribute this to the formation of mesoscopic fluctuating domains due to the coupling between local strain and quantum ferroelectric fluctuations. Thus, a hallmark of the ground state of insulating SrTiO$_3$ is the emergence of hybridized optical-acoustic phonons. Mesoscopic fluctuating domains play a role in quantum tunneling, which impedes the emergence of a finite macroscopic polarisation.
