Charge density wave (CDW) transition in Eu(Ga,Al)4 series studied by diffraction and inelastic x-ray scattering

Date

Dec 11, 2023

Time

2:50 PM - 4:20 PM

Speaker

Artem Korshunov

Affiliation

ESRF

Series

TUD Physik-IFMP Institutsseminar

Language

en

Main Topic

Physik

Other Topics

Physik

Host

D. Peets

Description

Abstract:

The intermetallic Eu(Ga,Al)4 system has recently attracted attention due to its nontrivial magnetic transitions and the emergence of a CDW state [1]. Its crystal structure adopts the BaAl4 structure type with tetragonal symmetry of I4/mmm space group. As an example, EuAl4 undergoes an incommensurate CDW transition with propagation vector qCDW ≈ (0, 0, 0.18) below TCDW = 145 K [2]. Remarkably, external pressure can entirely suppress this state in EuAl4, while the CDW in EuGa₄ can only be induced by pressure. The CDW modulation is associated with atomic displacements within the ab plane; however, the localization of the CDW remains unclear. Concurrently, the Fermi surface does not exhibit a clear instability at qCDW that is responsible for the CDW. Recent density functional theory calculations [3] suggest that strong electron-phonon coupling may be the driving force for the CDW, but this awaits experimental evidence.

In this study, we aim to shed light on the origin of the CDW in the Eu(Ga,Al)4 series. We have traced changes in crystal structure and diffuse scattering during the CDW transition by means of single crystal synchrotron diffraction at the ID28 beamline (ESRF). Additionally, using inelastic x-ray scattering, we measured phonon dispersions for several temperatures. Our findings reveal a pronounced softening of a transverse acoustic phonon near qCDW over a broad temperature range, providing crucial insights into CDW formation in isostructural compounds.

[1] Nakamura, Ai, et al., Transport and magnetic properties of EuAl4 and EuGa4, JPSJ 84(12), 124711 (2015)

[2] Ramakrishnan, S., et al., Orthorhombic charge density wave on the tetragonal lattice of EuAl4, IUCrJ 9(3), 378 (2022).

[3] Wang, L, et al. Origin of Charge Density Wave in Topological Semimetals SrAl4 and EuAl4, arXiv:2306.15068 (2023).

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Links

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Last modified: Dec 11, 2023, 7:36:17 AM