Coexistence of charge density wave and field-tuned magnetic states in TmNiC$_2$

TL;DR

This study investigates how charge density waves coexist with various magnetic states in TmNiC$_2$, revealing that the CDW persists across different magnetic phases due to electron-phonon interactions, despite deteriorating nesting conditions.

Contribution

It provides experimental evidence of the coexistence of charge density waves with multiple magnetic states in TmNiC$_2$, supported by electronic and phonon structure calculations.

Findings

Charge density wave persists in all magnetic phases.

Magnetic states do not weaken the CDW.

Electron-phonon coupling drives the CDW transition.

Abstract

Exploring the relations between coexisting, cooperative, or competing types of ordering is a key to identify and harness the mechanisms governing the mutual interactions between them, and to utilize their combined properties. We have experimentally explored the response of the charge density wave (CDW) to various antiferromagnetic, metamagnetic, and field-aligned ferromagnetic states that constitute the magnetic phase diagram of TmNiC$_2$. The high resolution x-ray diffraction experiment employing synchrotron radiation at low temperature and high magnetic field, allowed to follow the superstructure satellite reflections, being a sensitive probe of CDW. This investigation not only reveals direct evidence that the charge density wave avoids even a partial suppression in the antiferromagnetic ground state but also proves that this state coexists, without any visible signatures of weakening, in the entire dome of the magnetically ordered phases, including the field-aligned ferromagnetic state. The calculations of the electronic and phonon structures support the experiment, revealing that the dominant contribution to the CDW transition stems from momentum-dependent electron-phonon coupling. We conclude that this mechanism prevents the CDW from vanishing, although the nesting conditions within the magnetically ordered phases deteriorate.