Hidden Order in the Inhomogeneous Electronic State in Y-Based Superconducting Cuprate Oxide

为了研究高温超导体中的纳米级电子有序，我们对YBa_2Cu_3O_y单晶进行了低温扫描隧道显微镜（STM）实验。由于载流子库的不完全性，使得未掺杂的CuO_2面的载流子不能充分地掺杂到最上面的CuO_2面，利用解理面的优势，通过BaO表面研究了欠掺杂的CuO_2面的电子态。在低于20 mV的低偏压下测量的STM图像显示了沿Cu-O键沿着的一维（1D）电子调制。1D调制不具有长程有序，并且周期性取决于表面上的位置而在~2a-4a的范围内变化。这些结果表明，欠掺杂YBa_2Cu_3O_y中的电子有序不同于Bi_2Sr_2CaCu_2O_y和Ca_ Na_xCuO_2Cl_2中观察到的4aX 4a棋盘结构<2-x>。

To study the nanoscale electronic order in high-T_c superconductors, we have performed low-temperature scanning tunneling microscopy (STM) experiments on YBa_2Cu_3O_y single crystals. The electronic state of the underdoped CuO_2 plane is studied through the BaO surface taking advantage of the cleaved surface, which has an insufficient carrier doping into the topmost CuO_2 plane because of the incomplete carrier reservoir. The STM image measured at low bias-voltage below 20 mV shows the one-dimensional (1D) electronic modulation along the Cu-O bonds. The 1D modulation do not have long-range order and the periodicity varies within the range~2a-4a depending on the position on the surface. These results indicate that electronic order in underdoped YBa_2Cu_3O_y differs from the 4aX4a checkerboard structure observed in Bi_2Sr_2CaCu_2O_y and Ca_<2-x>Na_xCuO_2Cl_2.