Ferroelectric domain walls (DWs) are nanoscale topological defects that can be easily tailored to create nanoscale devices. Their excitations, recently discovered to be responsible for GHz DW conductivity, hold promise for faster signal transmission and processing compared to the existing technology. Here we find that DW phonons have unprecedented dispersion going from GHz all the way to THz frequencies, and resulting in a surprisingly broad GHz signature in DW conductivity. Puzzling activation of nominally forbidden DW sliding modes in BiFeO₃ is traced back to DW tilting and resulting asymmetry in wall-localized phonons. The obtained phonon spectra and selection rules are used to simulate scanning impedance microscopy, emerging as a powerful probe in nanophononics. The results will guide the experimental discovery of the predicted phonon branches and design of DW-based nanodevices operating in the technologically important frequency range.

铁电畴壁（DW）是纳米级拓扑缺陷，可以轻松定制以创建纳米级器件。最近发现它们的激发与GHz DW电导率有关，与现有技术相比，它们有望实现更快的信号传输和处理。在这里，我们发现DW声子从GHz一直到THz频率都具有空前的色散，并导致DW电导率中令人惊讶的宽GHz信号。令人费解的名义上禁止DW滑动模式中的激活的BiFeO ₃可以追溯到DW倾斜和壁局部声子的不对称性。获得的声子光谱和选择规则用于模拟扫描阻抗显微镜，是纳米声子学中功能强大的探针。结果将指导对预测的声子分支的实验发现以及在技术上重要的频率范围内运行的基于DW的纳米器件的设计。