arXiv subjects

Aikaterini Flessa Savvidou

Publications and source records attributed to Aikaterini Flessa Savvidou.

5 recordsLinked to original sources

arXiv2025

A Synthesizability-Guided Pipeline for Materials Discovery

Computational materials discovery relies on the generation of plausible crystal structures. The plausibility is typically judged through density functional theory methods which, while typically accurate at zero Kelvin, often favor low-energy structures that are not experimentally accessible. We develop a combined compositional and structural synthesizability score which provides an accurate way of predicting which compounds can actually be synthesized in a laboratory. We use it to evaluate non-synthesized structures from the Materials Project, GNoME, and Alexandria, and identified several hundred highly synthesizable candidates. We then predict synthesis pathways, conduct corresponding experiments, and characterize the products across 16 targets, successfully synthesizing 7 of 16. The entire experimental process was completed in only three days. Our results highlight omissions in lists of known synthesized structures, deliver insights into the practical utility of current materials databases, and showcase the central role synthesizability prediction can play in materials discovery.

cs.CE↗

arXiv2025

Diverse Magnetic Phase Diagram and Anomalous Hall Effect in Antiferromagetic LuMn$_6$Sn$_6$

The interactions between conduction electrons and magnetism can significantly enhance the Hall signal, a phenomenon known as the anomalous Hall effect (AHE). While the AHE is generally not expected in antiferromagnets, a large AHE is observed in certain antiferromagnets with noncollinear spin textures and nonvanishing Berry curvature. In this work, we present a rich temperature and magnetic phase diagram with eight distinct magnetic phases for the antiferromagnetic kagome compound LuMn$_6$Sn$_6$. The Hall effect analysis in LuMn$_6$Sn$_6$ reveals both intriguing physical phenomena and methodological challenges. In the coplanar canted antiferromagnetic phase, we observe an AHE, which likely originates from the intrinsic effects. At low temperatures, upon entering the ferromagnetic phase, the AHE sharply increases and exceeds the conventional limits expected from intrinsic mechanisms. We also demonstrate the limitations of standard experimental methods in extracting the topological contribution to the Hall effect data. We show the importance of considering magnetoresistance anisotropy when estimating the anomalous and topological Hall effects. These shortcomings in current approaches in partitioning the Hall response necessitate new tools to interpret transport results in complex magnetic materials such as LuMn$_6$Sn$_6$.

cond-mat.str-el↗

arXiv2023

Anisotropic positive linear and sub-linear magnetoresistivity in the cubic type-II Dirac metal Pd$_3$In$_7$

We report a transport study on Pd$_3$In$_7$ which displays multiple Dirac type-II nodes in its electronic dispersion. Pd$_3$In$_7$ is characterized by low residual resistivities and high mobilities, which are consistent with Dirac-like quasiparticles. For an applied magnetic field $(μ_{\text{0}} H)$ having a non-zero component along the electrical current, we find a large, positive, and linear in $μ_{\text{0}} H$ longitudinal magnetoresistivity (LMR). The sign of the LMR and its linear dependence deviate from the behavior reported for the chiral-anomaly-driven LMR in Weyl semimetals. Interestingly, such anomalous LMR is consistent with predictions for the role of the anomaly in type-II Weyl semimetals. In contrast, the transverse or conventional magnetoresistivity (CMR for electric fields $\textbf{E} \bot μ_{\text{0}} \textbf{H}$) is large and positive, increasing by $10^3-10^4$ \% as a function of $μ_{\text{0}}H$ while following an anomalous, angle-dependent power law $ρ_{\text{xx}}\propto (μ_{\text{0}}H)^n$ with $n(θ) \leq 1$. The order of magnitude of the CMR, and its anomalous power-law, is explained in terms of uncompensated electron and hole-like Fermi surfaces characterized by anisotropic carrier scattering likely due to the lack of Lorentz invariance.

cond-mat.mes-hall↗

arXiv2021

Evidence of a coupled electron-phonon liquid in NbGe$_2$

Whereas electron-phonon scattering typically relaxes the electron's momentum in metals, a perpetual exchange of momentum between phonons and electrons conserves total momentum and can lead to a coupled electron-phonon liquid with unique transport properties. This theoretical idea was proposed decades ago and has been revisited recently, but the experimental signatures of an electron-phonon liquid have been rarely reported. We present evidence of such a behavior in a transition metal ditetrelide, NbGe$_2$, from three different experiments. First, quantum oscillations reveal an enhanced quasiparticle mass, which is unexpected in NbGe$_2$ due to weak electron-electron correlations, hence pointing at electron-phonon interactions. Second, resistivity measurements exhibit a discrepancy between the experimental data and calculated curves within a standard Fermi liquid theory. Third, Raman scattering shows anomalous temperature dependence of the phonon linewidths which fits an empirical model based on phonon-electron coupling. We discuss structural factors, such as chiral symmetry, short metallic bonds, and a low-symmetry coordination environment as potential sources of coupled electron-phonon liquids.

cond-mat.mtrl-sci↗

arXiv2021

Complex Dirac-like Electronic Structure in Atomic Site Ordered Rh3In3.4Ge3.6

We report the synthesis via an indium flux method of a novel single-crystalline compound Rh3In3.4Ge3.6 that belongs to the cubic Ir3Ge7 structure type. In Rh3In3.4Ge3.6, the In and Ge atoms choose to preferentially occupy, respectively, the 12d and 16f sites of the Im-3m space group, thus creating a colored version of the Ir3Ge7 structure. Like the other compounds of the Ir3Ge7 family, Rh3In3.4Ge3.6 shows potential as a thermoelectric displaying a relatively large power factor, PF ~ 2 mW/cmK2, at a temperature T ~ 225 K albeit showing a modest figure of merit, ZT = 8 x 10-4, due to the lack of a finite band gap. These figures might improve through a use of chemical substitution strategies to achieve band gap opening. Remarkably, electronic band structure calculations reveal that this compound displays a complex Dirac-like electronic structure relatively close to the Fermi level. The electronic structure is composed of several Dirac type-I and type-II nodes, and even Dirac type-III nodes that result from the touching between a flat band and a linearly dispersing band. This rich Dirac-like electronic dispersion offers the possibility to observe Dirac type-III nodes and study their role in the physical properties of Rh3In3.4Ge3.6 and related Ir3Ge7-type materials.

cond-mat.mtrl-sci↗