Interaction of in-plane Drude carrier with c-axis phonon in PdCoO2

Dongmin Seo, Gihyeon Ahn, Gaurab Rimal, Seunghyun Khim, Suk Bum Chung, A. P. Mackenzie, Seongshik Oh, S. J. Moon, Eunjip Choi

Research output: Contribution to journalArticlepeer-review


We performed polarized reflection and transmission measurements on the layered conducting oxide PdCoO2 thin films. For the a b-plane, an optical peak near Ω ≈ 750 cm−1 drives the scattering rate 1/τ(ω) and effective mass m *(ω) of the Drude carrier to increase and decrease respectively for ω ≧ Ω. For the c-axis, a longitudinal optical phonon (LO) is present at Ω as evidenced by a peak in the loss function Im[−1/ε c(ω)]. Further polarized measurements in different light propagation (q) and electric field (E) configurations indicate that the Peak at Ω results from an electron-phonon coupling of the a b-plane carrier with the c-LO phonon, which leads to the frequency-dependent 1/τ(ω) and m *(ω). This unusual interaction was previously reported in high-temperature superconductors (HTSC) between a non-Drude, mid-infrared (IR) band and a c-LO. On the contrary, it is the Drude carrier that couples in PdCoO2. The coupling between the a b-plane Drude carrier and c-LO suggests that the c-LO phonon may play a significant role in the characteristic a b-plane electronic properties of PdCoO2, including the ultra-high dc-conductivity, phonon-drag, and hydrodynamic electron transport.

Original languageEnglish
Article number74
Journalnpj Quantum Materials
Issue number1
StatePublished - Dec 2023


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