Fig. 4: Observation of the properties of point-gap topology of the non-Hermitian Hamiltonian \({H}_{2}\) .
From: Multi-dimensional band structure spectroscopy in the synthetic frequency dimension
The left column illustrates \(L\left(\alpha =1,\,{\rm{\delta }}k\right)\) where the winding numbers are defined. The right column shows the winding diagrams. The gray solid lines in the right column are theoretical results. A complex energy on the right is related to its location in the Brillouin zone on the left by the color. a \({\rm{\delta }}k=-{\rm{\pi }}/2\), b \({\rm{\delta }}k=0\), c \({\rm{\delta }}k={\rm{\pi }}/4\), d \({\rm{\delta }}k={\rm{\pi }}/2\), e \({\rm{\delta }}k={\rm{\pi }}\)
