arXiv subjects

Adrien Rosuel

Publications and source records attributed to Adrien Rosuel.

4 recordsLinked to original sources

arXiv2026

Comment on: Microscopic signatures of an imaginary charge density wave in a kagome metal

Recently, Suetsugu $\textit{at al.}$ reported microscopic signatures of an imaginary charge density wave (iCDW) and TRSB in CsV$_3$Sb$_5$ at $T^* \approx 120$ K, attributing nuclear quadrupole resonance (NQR) linewidths and asymmetric Zeeman-perturbed NQR (Zp-NQR) lineshapes to chiral loop currents in [arXiv:2605.05101; https://doi.org/10.1038/s41567-026-03339-8]. In this Comment, we demonstrate that these observations are not evidence of exotic physics but are instead fully explained by crystalline mosaicity and pre-transitional CDW fluctuations. Through exact diagonalization of the full nuclear-spin Hamiltonian, we show that the observed asymmetric lineshapes arise naturally from an angular mosaic spread in the Zp-NQR regime, completely reproducing the data without the need for internal magnetic fields. Furthermore, we reveal that the reported emergent local field ($h_{\text{loc}}$) is an artifact resulting from unjustified and unreported fitting constraints, and the use of an approximate perturbative model. Strikingly, we point out that this local-field model required for the proposed iCDW produces features that are absent in the data. Addressing the recent Reply by Suetsugu $\textit{at al.}$ [arXiv:2608.24927v1], we show that these core issues remain unresolved: the linewidth follows a standard Curie-Weiss law with no phase transition at $T^*$, and their definition of mosaicity overlooks well-documented strain-mediated lattice distortions. Most critically, when the full Hamiltonian is solved exactly and the artificial fitting constraints are removed, the inferred loop-current signature vanishes ($h_{\text{loc}} \to 0$). We therefore conclude that the claim of an iCDW state in in Ref. [arXiv:2605.05101; https://doi.org/10.1038/s41567-026-03339-8] is unsupported by the data, arising instead from incomplete spectral simulations and inadequate theoretical modeling.

cond-mat.str-el↗

arXiv2026

Orbital glass conceals missing magnetic entropy in a relativistic Mott insulator

Coupling between different degrees of freedom (DOF) in an electronic material leads to exotic phases of matter characterized by complex and competing order parameters as well as emergent excitations. Building a microscopic understanding of these order parameters and their mutual relationship is hindered by the fact that different orders often mask each others' response to conventional experimental probes. Here, we reveal how to disentangle responses from distinct orders that arise from the coupling between the spin and orbital DOF. Our method uses a phase sensitive technique that measures ground state properties by independently resolving interactions of different symmetries. This allows us to directly detect an orbital glass state caused by competing interactions in the $5d^1$ relativistic Mott insulator Ba$_2$NaOsO$_6$. We observe short-range orbital order up to 380 K and a dramatic increase of orbital dispersion near the magnetic phase transition. This orbital dispersion generates a directional ordering, $\textit{i.e.}$, it forms an orbital nematic state which breaks the rotational symmetry of the crystal. We establish that the orbital nematic state induces the magnetic ordering. The presence of this short-range orbital order well above the magnetic phase transition solves the long-standing puzzle of missing entropy in this material.

cond-mat.str-el↗

arXiv2025

Observation of ubiquitous charge correlations and hidden quantum critical point in hole-doped kagome superconductors

The interplay between superconductivity and charge-density wave (CDW) order, and its evolution with carrier density, is central to the physics of many quantum materials, notably high-$T_c$ cuprates and kagome metals. Hole-doped kagome compounds exhibit puzzling double-dome superconductivity and, as chemical substitution inevitably introduces quenched disorder, their properties remain poorly understood. Here, by leveraging the sensitivity of nuclear quadrupole resonance to local and static orderings, we uncover new features, primarily the incipient and fragmented CDW phases, in the charge landscape of CsV$_3$Sb$_{5-x}$Sn$_x$. Static CDW puddles are observed well above the transition temperature, a hallmark of pinning by defects. Their doping and temperature evolution indicate that, in the absence of disorder, the inverse Star-of-David $\pi$-shifted (ISD-$\pi$) CDW order would vanish near $x=0.12$, between the two superconducting domes. This critical doping represents a hidden quantum critical point. Nevertheless, the ISD-$\pi$ pattern persists well beyond previous reports, although its volume fraction is progressively reduced up to the critical doping at which it saturates. We establish that carrier doping promotes fragmentation of the ISD-$\pi$ order, whereas randomness preserves the ISD-$\pi$ patches.

cond-mat.str-el↗

arXiv2023

Field-induced tuning of the pairing state in a superconductor

The recently discovered superconductor UTe$_2$, with a T$_c$ between 1.5~K and 2~K, is attracting much attention due to strong suspicion of spin-triplet and topological superconductivity. Its properties under magnetic field are also remarkable, with field-reinforced and field-induced superconducting phases. Here, we report the first complete thermodynamic determination of the phase diagram for fields applied along the three crystallographic directions. Measurements were performed up to 36~T along the hard magnetisation $b$~axis in order to follow the superconducting transition up to the metamagnetic transition at $H_{m} = 34.75$~T. They reveal the existence of a phase transition line within the superconducting phase, and drastic differences occurring between these two phases. Detailed analysis supports a different spin state between the two phases, implying a low-field spin-triplet to high-field spin-singlet transition, a unique case among superconductors, giving insight on the mechanisms leading to spin-triplet superconductivity.

cond-mat.supr-con↗