Highly fluctuating double-$q$ magnetic order in the van der Waals metal CeTe$_3$

TL;DR

CeTe$_3$ exhibits a complex, fluctuating double-$q$ magnetic order at low temperatures, with quantum fluctuations and charge-density-wave interactions influencing its magnetic state.

Contribution

This study reveals the nature of the low-temperature magnetic order in CeTe$_3$, highlighting its fluctuating double-$q$ structure and coupling to charge-density-wave instabilities.

Findings

Incommensurate Bragg peaks at $q_{ ext{±}} extasciitilde( ext{±}0.17,0,0.31)$ indicate a double-$q$ magnetic order.

Reduced ordered moments suggest strong quantum fluctuations due to $c$-$f$ hybridization.

Coupling to charge-density-wave instabilities affects the magnetic propagation vectors.

Abstract

CeTe$_3$ is a van der Waals antiferromagnet composed of magnetic [CeTe]$^+$ layers coupled to highly conducting Te$^{0.5-}$ square nets. Its simple quasi-two-dimensional electronic structure and cleavable nature make it an appealing platform for exploring correlated magnetism in reduced dimensions. To clarify the nature of its low-temperature state, we performed single-crystal neutron diffraction down to 0.3 K, complemented by scanning tunneling microscopy. A magnetic transition near 1.5 K gives rise to incommensurate Bragg peaks at $q_{\pm}\sim(\pm0.17,0,0.31)$, consistent with a double-$q$ magnetic order whose moments are predominantly aligned along the $c$ axis. The strongly reduced ordered moment is consistent with enhanced quantum fluctuations driven by $c$-$f$ hybridization, while the deviation of the propagation vectors from simple nesting suggests a coupling to residual charge-density-wave instabilities of the quasi-one-dimensional Te-derived bands. These results indicate that CeTe$_3$ hosts a correlated magnetic ground state where spin and itinerant charge degrees of freedom are intimately linked in the van der Waals limit.