Investigating Josephson plasmons in layered cuprates via nonlinear terahertz spectroscopy

TL;DR

This paper explores the nonlinear optical properties of Josephson plasmons in layered cuprates using terahertz spectroscopy, revealing new selection rules and potential for THz pulse generation.

Contribution

It derives the selection rules for nonlinear plasmonics in layered superconductors and demonstrates how plasmon dispersion influences the nonlinear THz response in cuprates.

Findings

Nonlinear THz response depends on plasmon dispersion and light polarization.

Selection rules reveal plasmonic branches hidden to other spectroscopies.

Potential for generating THz pulses with engineered Josephson heterostructures.

Abstract

Josephson plasmons in layered superconductors represent a natural source of optical non-linearity, thanks to their intrinsically anharmonic nature. Here we derive the selection rules behind non-linear plasmonics showing its dependence on plasmonic branches hidden to other spectroscopies, like RIXS. We benchmark our results for the case of layered cuprates, showing how in a layered system the combined effect of plasmon dispersion and light polarization can move the resonance of the bilayer system away from the plasma edge measured in linear spectroscopy. Our results demonstrate the dependence of the non-linear THz response on the convoluted plasmon dispersion in a momentum region complementary to RIXS, and offer a possible perspective for the generation of THz pulses by artificially designed Josephson heterostructures.