Ferromagnetism emerged from non-ferromagnetic atomic crystals.

The recently emerged ferromagnetic two-dimensional (2D) materials provide unique platforms for compact spintronic devices down to the atomic-thin regime; however, the prospect is hindered by the limited number  of ferromagnetic 2D materials discovered with limited choices of magnetic properties. If 2D antiferromagnetism could be converted to 2D ferromagnetism, the range of 2D magnets and their potential applications would be significantly broadened. Here, we discovered emergent ferromagnetism by interfacing non-magnetic WS layers with the antiferromagnetic FePS.

Exploring magneto-optic properties of colloidal two-dimensional copper-doped CdSe nanoplatelets.

Transition-metal-doped semiconductor nanocrystals have received significant attention because of their attractive features deeming them invaluable in various technological fields including optoelectronics, bio-photonics, and energy conversion, to name a few. Of particular, these interests are two-dimensional materials with useful optical and magnetic properties combined with their large surface areas opening up new applications in biotechnology. These applications range from multimodal optical and magnetic bioimaging and sensing to measuring the weak magnetic field due to brain waves using their magneto-optic properties stemming from the exchange interaction between the transition metal dopants and the carrier spins.

Transition metal dichalcogenide graded alloy monolayers by chemical vapor deposition and comparison to 2D Ising model.

In this work, a chemical vapor deposition (CVD) method was developed for the synthesis of transition metal dichalcogenide alloy monolayers, with a composition gradient in the radial direction. The composition gradient was achieved by controlling the substrate cooling rate during the CVD growth. The two types of alloys, namely, WSSe and MoSSe, were found to exhibit an opposite composition gradient.

Light-Induced Paramagnetism in Colloidal Ag-Doped CdSe Nanoplatelets.

We describe a study of the magneto-optical properties of Ag-doped CdSe colloidal nanoplatelets (NPLs) that were grown using a novel doping technique. In this work, we used magnetic circularly polarized luminescence and magnetic circular dichroism spectroscopy to study light-induced magnetism for the first time in 2D solution-processed structures doped with nominally nonmagnetic Ag impurities. The excitonic circular polarization () and the exciton Zeeman splitting () were recorded as a function of the magnetic field () and temperature ().

Giant valley splitting in monolayer WS by magnetic proximity effect.

Lifting the valley degeneracy of monolayer transition metal dichalcogenides (TMDs) would allow versatile control of the valley degree of freedom. We report a giant valley exciton splitting of 16 meV/T for monolayer WS, using the proximity effect from an EuS substrate, which is enhanced by nearly two orders of magnitude from that obtained by an external magnetic field. More interestingly, a sign reversal of the valley splitting is observed as compared to that of WSe on EuS.

Enhanced valley splitting in monolayer WSe due to magnetic exchange field.

Exploiting the valley degree of freedom to store and manipulate information provides a novel paradigm for future electronics. A monolayer transition-metal dichalcogenide (TMDC) with a broken inversion symmetry possesses two degenerate yet inequivalent valleys, which offers unique opportunities for valley control through the helicity of light. Lifting the valley degeneracy by Zeeman splitting has been demonstrated recently, which may enable valley control by a magnetic field.

Mn(2+)-Doped CdSe/CdS Core/Multishell Colloidal Quantum Wells Enabling Tunable Carrier-Dopant Exchange Interactions.

In this work, we report the manifestations of carrier-dopant exchange interactions in colloidal Mn(2+)-doped CdSe/CdS core/multishell quantum wells. The carrier-magnetic ion exchange interaction effects are tunable through wave function engineering. In our quantum well heterostructures, manganese was incorporated by growing a Cd0.

Templated synthesis of ZnSe nanostructures using lyotropic liquid crystals.

We report a technique for controlled synthesis of zero-, one-, and two-dimensional compound semiconductor nanostructures by using cubic, hexagonal, and lamellar lyotropic liquid crystals as templates, respectively. The liquid crystals were formed by self-assembly in a ternary system consisting of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) amphiphilic block copolymer as the surfactant, heptane as the non-polar dispersed phase, and formamide as the polar continuous phase. ZnSe quantum dots and nanowires with diameters smaller than 10 nm, as well as free-standing, disc-like quantum wells, were grown inside the spherical, cylindrical, and planar nanodomains, respectively, by reacting diethylzinc that was dissolved in the heptane domains with hydrogen selenide gas that was brought into contact with the liquid crystal in a sealed chamber at room temperature and atmospheric pressure.

Synthesis and size control of luminescent ZnSe nanocrystals by a microemulsion-gas contacting technique.

A scalable method for controlled synthesis of luminescent compound semiconductor nanocrystals (quantum dots) using microemulsion-gas contacting at room temperature is reported. The technique exploits the dispersed phase of a microemulsion to form numerous identical nanoreactors. ZnSe quantum dots were synthesized by reacting hydrogen selenide gas with diethylzinc dissolved in the heptane nanodroplets of a microemulsion formed by self-assembly of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) amphiphilic block copolymer in formamide.

Electrical spin injection from an n-type ferromagnetic semiconductor into a III-V device heterostructure.

The use of carrier spin in semiconductors is a promising route towards new device functionality and performance. Ferromagnetic semiconductors (FMSs) are promising materials in this effort. An n-type FMS that can be epitaxially grown on a common device substrate is especially attractive.