Evidence for strongly coupled charge-density-wave ordering in three-dimensional RE5Ir4Si10 compounds by optical measurements

TL;DR

This study uses optical spectroscopy to reveal strong electron-phonon coupling and partial Fermi surface gapping due to charge density wave order in three-dimensional RE5Ir4Si10 compounds, coexisting with superconductivity or magnetism.

Contribution

It provides direct optical evidence of strongly coupled CDW order in 3D RE5Ir4Si10 compounds, quantifying the CDW gap and electron-phonon interaction strength.

Findings

Charge density wave gap ratio 2Δ/k_B T_CDW ≈ 10

Electron-phonon coupling constant λ ≈ 2.6

Approximately 16% of the Fermi surface is gapped in the CDW state

Abstract

We report optical spectra of Lu$_5$Ir$_4$Si$_{10}$ and Er$_5$Ir$_4$Si$_{10}$, exhibiting the phenomenon of coexisting superconductivity or antiferromagnetism and charge density wave (CDW) order. We measure the maximum value of the charge density wave gap present on part of the Fermi surface of Lu5Ir4Si10, corresponding to a ratio 2\Delta/k_B T_CDW \approx 10, well above the value in the limit of weak electron-phonon coupling. Strong electron-phonon coupling was confirmed by analyzing the optical conductivity with the Holstein model describing the electron-phonon interactions, indicating the coupling to phonons centered at 30 meV, with a coupling constant \lambda \approx 2.6. Finally we provide evidence that approximately 16 % of the Fermi surface of Lu5Ir4Si10 becomes gapped in the CDW state.