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This study investigates the electronic structure of the vanadium-based kagome metal YV6Sn6 using magnetoresistance (MR) and torque magnetometry. The MR exhibits a nearly linear, non-saturating behavior, increasing by up to 55% at 35 T but shows no evidence of Shubnikov–de Haas oscillations. In contrast, the torque signal, measured up to 41.5 T, reveals clear de Haas–van Alphen (dHvA) oscillations over a wide frequency range, from a low frequency of Fα ∼20 T to high frequencies between 8 and 10 kT. Angular and temperature-dependent dHvA measurements were performed to probe the Fermi surface parameters of YV6Sn6. The dHvA frequencies display weak angular dependence, and the effective mass, determined by fitting the temperature-dependent data to the Lifshitz–Kosevich formula, is 0.097 mo, where mo represents the free electron mass. To complement the experimental findings, we computed the electronic band structure and Fermi surface using density functional theory. The calculations reveal several notable features, including multiple Dirac points near the Fermi level, flatbands, and Van Hove singularities. Two bands cross the Fermi level, contributing to the Fermi surface, with theoretical frequencies matching well with the observed dHvA frequencies. These combined experimental and theoretical insights enhance our understanding of the electronic structure of YV6Sn6 and provide a valuable framework for studying other vanadium- and titanium-based kagome materials. 

Abstract Kagomé metals are widely recognized, versatile platforms for exploring topological properties, unconventional electronic correlations, magnetic frustration, and superconductivity. In theRV₆Sn₆family of materials (R= Sc, Y, Lu), ScV₆Sn₆hosts an unusual charge density wave ground state as well as structural similarities with theAV₃Sb₅system (A= K, Cs, Rb). In this work, we combine Raman scattering spectroscopy with first-principles lattice dynamics calculations to reveal phonon mixing processes in the charge density wave state of ScV₆Sn₆. In the low temperature phase, we find at least four new peaks in the vicinity of the V-containing totally symmetric mode near 240 cm⁻¹suggesting that the density wave acts to mix modes ofP6/mmmand$$R\bar{3}m$$ $R\overline{3}m$symmetry - a result that we quantify by projecting phonons of the high symmetry state onto those of the lower symmetry structure. We also test the stability of the short-range ordered density wave state under compression and propose that both physical and chemical pressure quench the effect. We discuss these findings in terms of symmetry and the structure-property trends that can be unraveled in this system. 

Abstract Metals with kagome lattice provide bulk materials to host both the flat-band and Dirac electronic dispersions. A new family of kagome metals is recently discovered inAV₆Sn₆. The Dirac electronic structures of this material needs more experimental evidence to confirm. In the manuscript, we investigate this problem by resolving the quantum oscillations in both electrical transport and magnetization in ScV₆Sn₆. The revealed orbits are consistent with the electronic band structure models. Furthermore, the Berry phase of a dominating orbit is revealed to be aroundπ, providing direct evidence for the topological band structure, which is consistent with calculations. Our results demonstrate a rich physics and shed light on the correlated topological ground state of this kagome metal. 

Abstract Whereas electron-phonon scattering relaxes the electron’s momentum in metals, a perpetual exchange of momentum between phonons and electrons may conserve total momentum and lead to a coupled electron-phonon liquid. Such a phase of matter could be a platform for observing electron hydrodynamics. Here we present evidence of an electron-phonon liquid in the transition metal ditetrelide, NbGe₂, from three different experiments. First, quantum oscillations reveal an enhanced quasiparticle mass, which is unexpected in NbGe₂with weak electron-electron correlations, hence pointing at electron-phonon interactions. Second, resistivity measurements exhibit a discrepancy between the experimental data and standard Fermi liquid calculations. Third, Raman scattering shows anomalous temperature dependences of the phonon linewidths that fit 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 design principles for materials with coupled electron-phonon liquid.