First results of quasiparticle interference visualized by high-spatial-resolution photoemission electron microscopy

Quasiparticle interference (QPI) reveals essential electronic properties but has remained limited to static measurements with scanning tunneling microscopy. Here, we report the first observation of QPI using our newly developed low-temperature photoemission electron microscopy, a technique inherently suited for dynamical studies. Although the intrinsic QPI wavelength is smaller than our instrument's resolution, we detect a distinct dark line at the atomic step edge. Contrast transfer function modeling confirms that this line arises from the convolution of QPI-induced local density of states modulations with both imaging system response and detector effects. We further demonstrate that resolving finer QPI patterns is feasible with enhanced resolution. Our work establishes a new paradigm for time- and momentum-resolved QPI investigations, moving beyond static mapping to capture electronic dynamics in nonequilibrium quantum phenomena.