arXiv subjects

Mitsutaka Haruta

Publications and source records attributed to Mitsutaka Haruta.

3 recordsLinked to original sources

arXiv2026

Precisely positioned generation of CsPbBr3 nano-light sources in a Cs4PbBr6 film by electron beam irradiation

Integration of high-quality photon emitters at specific locations within nanophotonic structures or optoelectronic devices is a key to innovating on-chip optical control and quantum technologies. Halide perovskite nanoparticles have great potential as single photon emitters with high quantum efficiency. To achieve their full potential, they must be embedded in a host material that ensures chemical stability and passivates surface defects. A previous experiment on a CsPbBr3-Cs4PbBr6 nanocomposite film suggested possibility that electron beam irradiation can be used to control positions of CsPbBr3 nano-light sources in the Cs4PbBr6 host although the effects of electron beam irradiation are not fully understood. Here, we fabricate a Cs4PbBr6-CsBr film, not containing the CsPbBr3 phase, and provide direct evidence that CsPbBr3 nanoparticles can be locally generated in the Cs4PbBr6 host by irradiation with a focused electron beam. We further demonstrate perovskite nano-light source arrays with submicron spacing using this method.

cond-mat.mes-hall↗

arXiv2025

High-temperature helical edge states in BiSbTeSe$_2$/graphene van der Waals heterostructure

Van der Waals heterostructures have been used to tailor atomic layers into various artificial materials through interactions at heterointerfaces. The interplay between the band gap created by the band folding of the interfacial potential and the band inversion driven by enhanced spin-orbit interaction (SOI) through band hybridization enables us to realize a two-dimensional topological insulator (2D-TI). Here we report the realization of graphene 2D-TIs by epitaxial growth of three-dimensional topological insulator (3D-TI) BiSbTeSe$_2$ ultrathin films on graphene. By increasing the BiSbTeSe$_2$ thickness from 2 nm to 9 nm to enhance SOI on graphene, the electronic state is altered from the trivial Kekul${é}$ insulator to the 2D-TI. The nonlocal transport reveals the helical edge conduction which survives up to 200 K at maximum. Our graphene 2D-TI is stable, easy to make electrical contacts, and of high quality. It offers various applications including spin-current conversion and platforms for Majorana fermions in junctions to superconductors.

cond-mat.mes-hall↗

arXiv2023

Stabilization of Ferroelectric Hf0.5Zr0.5O2 Epitaxial Films via Monolayer Reconstruction Driven by Interfacial Redox Reaction

The binary fluorite oxide Hf0.5Zr0.5O2 tends to grab a significant amount of notice due to the distinct and superior ferroelectricity found in its metastable phase. Stabilizing the metastable ferroelectric phase and delineating the underlying growth mechanism, however, are still challenging. Recent discoveries of metastable ferroelectric Hf0.5Zr0.5O2 epitaxially grown on structurally dissimilar perovskite oxides have triggered intensive investigations on the ferroelectricity in materials that are nonpolar in bulk form. Nonetheless, the growth mechanism for the unique fluorite/perovskite heterostructures has yet to be fully explored. Here we show that the metastable ferroelectric Hf0.5Zr0.5O2 films can be stabilized even on a one-unit-cell-thick perovskite La0.67Sr0.33MnO3 buffer layer. In collaboration with scanning transmittance electron microscopy (STEM) based characterizations, we show that monolayer reconstruction driven by interfacial redox reactions plays a vital role in the formation of a unique heterointerface between the two structurally dissimilar oxides, providing the template monolayer that facilitates the epitaxial growth of the metastable HZO films. Our findings offer significant insights into the stabilization mechanism of the ferroelectric Hf0.5Zr0.5O2, and this mechanism could be extended for exploring functional metastable phases of various metal oxides.

cond-mat.mtrl-sci↗