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M. E. Kamminga

Publications and source records attributed to M. E. Kamminga.

2 recordsLinked to original sources

Coexisting Kondo and Weyl-like transport in kagome heavy-fermion metal, Yb$_y$Co$_3$G$e_{3-x}$Sn$_x$

Strong electron correlations and topology offer complementary routes to controlling electrical conduction, as correlations can make electrons heavy (e.g. Kondo lattices) whereas topology can make them behave as massless particles (e.g. Dirac or Weyl systems), and having both in one material is rare. In Kondo lattice systems, Kondo hybridization between localized 4$f$ and conduction electrons strongly enhances the quasiparticle mass, where in Weyl-Kondo systems these Kondo-renormalized bands form Weyl states, and simultaneous signs of both Kondo and Weyl states in one material have not been observed in transport. Here we report signs of both in the kagome metal \ce{Yb_yCo3Ge_{3-x}Sn_x} by combining magnetotransport, heat capacity, magnetization, angle-resolved and X-ray photoemission spectroscopy, and DFT+U calculations to reveal Yb-dependent Kondo scattering developing into lattice coherence, with extrapolated Sommerfeld coefficient of approximately 2 ~Jmol$_{\mathrm{Yb}}^{-1}$K$^{-2}$. Transverse magnetoresistance (MR) follows single-ion Kondo scaling, whereas longitudinal transport contains an additional negative response proportional to B$^2$ and remains unsaturated up to 32 T, consistent with a chiral anomaly. These findings support a picture of Kondo and Weyl-like conduction arising from distinct electronic states without external Fermi-level tuning, suggesting a possible route to combining correlated and topological functionality in a bulk material.

cond-mat.str-el↗

Microscopic origin of field-induced multiferroicity in Ni3TeO6

The continued demand for smaller, faster, and more energy-efficient technologies has driven condensed-matter research towards materials combining multiple responses within a single phase. Particularly interesting examples are multiferroic materials featuring cross-couplings between order parameters. Ni3TeO6 is a prominent member of this material class, exhibiting a hysteresis-free transition under magnetic field which simultaneously affects the magnetic structure, electric polarization, and phonon frequencies. Here, we uncover the microscopic origin of this multiferroic transition using a combination of neutron scattering techniques. We establish the presence of a finite Dzyaloshinskii-Moriya exchange term giving rise to non-reciprocal, chiral spin waves which soften in magnetic field. Their condensation alters the magnetic structure which controls the electric polarization and drives an ionic displacement, thereby coupling the magnetic, electric, and lattice degrees of freedom. Our study demonstrates that neutron scattering is a powerful technique to elucidate microscopic interactions in multiferroic materials, informing the design of next-generation electronic devices.

cond-mat.mtrl-sci↗