Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: Correlated Magnetism – Dynamics and Spectroscopy

TT 33.3: Talk

Tuesday, March 10, 2026, 11:30–11:45, HSZ/0105

Terahertz Time-Domain Spectroscopy of Coupled Spin and Low-Energy Excitations in CeCoGe₃ — •Debankit Priyadarshi¹, Zekai Chen¹, Erik W. de Vos¹, Geetha Balakrishnan², and Manfred Fiebig¹ — ¹ETH Zurich, Switzerland — ²University of Warwick, United Kingdom

We present a direct observation of the interaction between a low-frequency excitation and a spin-wave resonance [1] in the intermetallic heavy-fermion compound CeCoGe₃ using terahertz time-domain spectroscopy. CeCoGe₃ exhibits three low-temperature magnetic transitions at 21 K, 12 K and 8 K [2]. In addition to the observation of a magnon mode below the Nèel temperature at 1.04 THz, we find a temperature-independent low-frequency excitation at 0.4 THz. The absorption intensities of the low-frequency mode and the magnon mode suggest an inverse coupling effect which becomes strongest below the second magnetic transition at 12 K. This hints at strong magnon-phonon coupling emerging at low-temperatures. These results can therefore shed light on how lattice vibrations influence heavy-fermion magnetism. Additionally, optical-pump THz-probe measurements are performed to investigate the role of electronic excitations in order to understand the cross-talk between these three different fundamental degrees of freedom in inter-metallic systems.
[1] M. Smidman et al., PRB 88, 134416 (2013).
[2] A. Thamizhavel et al., J. Phys. Soc. Jpn. 74, 1858 (2005).

Keywords: Strongly-correlated materials; magnetic excitations; Terahertz (THz) spectroscopy; intermetallic alloy