Interest in many strongly spin-orbit-coupled 5d-transition metal oxide insulators stems from mapping their electronic structures to a J eff ¼ 1/2 Mott phase. One of the hopes is to establish their Mott parent states and explore these systems' potential of realizing novel electronic states upon carrier doping. However, once doped, little is understood regarding the role of their reduced Coulomb interaction U relative to their strongly correlated 3d-electron cousins. Here we show that, upon hole-doping a candidate J eff ¼ 1/2 Mott insulator, carriers remain localized within a nanoscale phase-separated ground state. A percolative metal-insulator transition occurs with interplay between localized and itinerant regions, stabilizing an antiferromagnetic metallic phase beyond the critical region. Our results demonstrate a surprising parallel between doped 5d-and 3d-electron Mott systems and suggest either through the near-degeneracy of nearby electronic phases or direct carrier localization that U is essential to the carrier response of this doped spin-orbit Mott insulator.

Germanane (GeH), a hydrogen-terminated layered germanium structure, has recently been synthesized. Here, we employed a four-probe thermal transport measurement method to obtain the basal-plane thermal conductivity of thin exfoliated GeH flakes and correlated the measurement results with the crystal structure. The obtained thermal conductivity increases with increasing temperature, suggesting that extrinsic grain boundary and defect scattering dominate over intrinsic phonon-phonon scattering. Annealing a polycrystalline GeH sample at 195 °C caused it to become amorphous, reducing the room-temperature thermal conductivity from 0.53 ± 0.09 W m−1 K−1, which is close to the value calculated for 16 nm grain size, to 0.29 ± 0.05 W m−1 K−1, which approaches the calculated amorphous limit in the basal plane thermal conductivity.

We present a first-principles theoretical approach to calculate temperature dependent phonon dispersions in bcc Fe, which captures finite temperature spin-lattice coupling by treating thermal disorder in both the spin and lattice systems simultaneously. With increasing temperature, thermal atomic displacements are found to induce increasingly large fluctuations in local magnetic moment magnitudes. The calculated phonon dispersions of bcc Fe show excellent agreement with measured data over a wide range of temperatures both above and below the magnetic and structural transition temperatures, suggesting the applicability of the developed approach to other magnetic materials.

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