Signature of $\mathcal{P}\mathcal{T}$-symmetric non-Hermitian superconductivity in angle-resolved photoelectron fluctuation spectroscopy

We show theoretically that the measurement of a $\mathcal{PT}$-symmetric non-Hermitian superconductor by angle-resolved photoelectron fluctuation spectroscopy (ARPFS) provides a particular signature. In fact, the signal is negative in a single-band case in contrast to the ARPFS signal of Hermitian superconductors. We suggest that the negative fluctuations can be explained by a remarkable pairing phenomenon: If the interaction between electrons in this $\mathcal{PT}$-symmetric non-Hermitian superconductor is attractive, then the interaction between holes (i.e., missing electrons) is repulsive and vice versa. This difference in the sign of the interactions gives rise to negative cross correlations. Here, we propose how such an electron-electron interaction can occur due to the spatiotemporal modulation of the material. We also discuss the observability of this signature in multiband systems.

Figure 1

Schematic of the ARPFS setup: An electromagnetic pulse is hitting onto the $\mathcal{PT}$-symmetric superconductor. Electrons are emitted from the substrate due to interaction with photons from the pulse and are registered by two detectors located at opposite sides of the sample. The aim of the detection scheme is to identify correlated electrons that formed a Cooper pair in the sample before they have left it.