Terahertz Spectra Revealing the Collective Excitation Mode in Charge‐Density‐Wave Single Crystal LuFe ₂ O ₄

Abstract

A low‐energy collective excitation mode in charge‐ordered multiferroic LuFe2O4 is reported via terahertz time‐domain spectroscopy. Upon cooling from 300 to 40 K, the central resonance frequency showed a pronounced hardening from 0.85 to 1.15 THz. In analogy to the well‐known low‐energy optical properties of LuFe2O4, this emerging resonance was attributed to the charge–density–wave (CDW) collective excitations. By using the Drude–Lorentz model fitting, the CDW collective mode becomes increasingly damped with the increasing temperature. Furthermore, the kinks of the CDW collective mode at the magnetic transition temperature are analyzed, which indicate the coupling of spin order with electric polarization.

Terahertz spectroscopic signature of the charge density wave in the spin-ladder compound, Sr14Cu24O41

“…Hence upon illumination with electromagnetic radiation, the CDW phason mode becomes visible in the complex optical spectrum. Since the CDW phason mode appears in the millimeter frequency range, THz spectroscopy has been previously used to study the CDW phason mode in manganites, nickelates, and multiferroic materials [11][12][13][14][15]. In most cases, the CDW phason peak appears in the few-meV energy range, along with a broad shoulder at lower energies.…”