Bert F, Bellessa G, Grushko B
Laboratoire de Physique des Solides, Université Paris-Sud, Bâtiment 510, 91405 Orsay, France.
Phys Rev Lett. 2002 Jun 24;88(25 Pt 1):255901. doi: 10.1103/PhysRevLett.88.255901. Epub 2002 Jun 10.
We present low-temperature measurements, between 20 mK and 20 K, of the sound velocity variations in a single grain of the decagonal quasicrystal Al-Ni-Co. We have used acoustic shear waves of frequency 70 MHz propagating in the quasicrystalline planes with two different polarizations: parallel and perpendicular to the quasicrystalline planes. Our results show the presence of tunneling states (TSs) with a strong difference of the phonon-TS coupling for the two polarizations, which reveals a strong anisotropy of distribution of the orientations of the TSs in the sample. This result gives direct evidence that TSs are generated by the quasicrystalline structure itself.
我们展示了在20毫开尔文至20开尔文之间对十边形准晶体Al-Ni-Co单晶粒中声速变化的低温测量结果。我们使用了频率为70兆赫兹的声学剪切波，该波在准晶平面中以两种不同极化方向传播：平行于和垂直于准晶平面。我们的结果表明存在隧穿态（TSs），对于这两种极化，声子-TS耦合存在很大差异，这揭示了样品中TSs取向分布的强烈各向异性。这一结果直接证明了TSs是由准晶结构本身产生的。
