Anomalous Nernst Effect Induced Terahertz Emission in a Single Ferromagnetic Film.

Despite its important role in understanding ultrafast spin dynamics and revealing novel spin/orbit effects, the mechanism of the terahertz (THz) emission from a single ferromagnetic nanofilm upon a femtosecond laser pump still remains elusive. Recent experiments have shown exotic symmetry, which is not expected from the routinely adopted mechanism of ultrafast demagnetization. Here, by developing a bidirectional pump-THz emission spectroscopy and associated symmetry analysis method, we set a benchmark for the experimental distinction of the THz emission induced by various mechanisms. Our results unambiguously unveil a new mechanism─anomalous Nernst effect (ANE) induced THz emission due to the ultrafast temperature gradient created by a femtosecond laser. Quantitative analysis shows that the THz emission exhibits interesting thickness dependence where different mechanisms dominate at different thickness ranges. Our work not only clarifies the origin of the ferromagnetic-based THz emission but also offers a fertile platform for investigating the ultrafast optomagnetism and THz spintronics.

Exploiting Spin Fluctuations for Enhanced Pure Spin Current.

We demonstrate the interplay of pure spin current, spin-polarized current, and spin fluctuation in 3d Ni_{x}Cu_{1-x}. By tuning the compositions of the Ni_{x}Cu_{1-x} alloys, we separate the effects due to the pure spin current and spin-polarized current. By exploiting the interaction of spin current with spin fluctuation in suitable Ni-Cu alloys, we obtain an unprecedentedly high spin Hall angle of 46%, about 5 times larger than that in Pt, at room temperature. Furthermore, we show that spin-dependent thermal transport via anomalous Nernst effect can serve as a sensitive magnetometer to electrically probe the magnetic phase transitions in thin films with in-plane anisotropy. The enhancement of spin Hall angle by exploiting spin current fluctuation via composition control makes 3d magnets functional materials in charge-to-spin conversion for spintronic application.

Negative circular polarization emissions from WSe2/MoSe2 commensurate heterobilayers.

Van der Waals heterobilayers of transition metal dichalcogenides with spin-valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications. The interlayer coupling was predicted to exhibit subtle changes with the interlayer atomic registry. Manually stacked heterobilayers, however, are incommensurate with the inevitable interlayer twist and/or lattice mismatch, where the properties associated with atomic registry are difficult to access by optical means. Here, we unveil the distinct polarization properties of valley-specific interlayer excitons using epitaxially grown, commensurate WSe2/MoSe2 heterobilayers with well-defined (AA and AB) atomic registry. We observe circularly polarized photoluminescence from interlayer excitons, but with a helicity opposite to the optical excitation. The negative circular polarization arises from the quantum interference imposed by interlayer atomic registry, giving rise to distinct polarization selection rules for interlayer excitons. Using selective excitation schemes, we demonstrate the optical addressability for interlayer excitons with different valley configurations and polarization helicities.

The effectiveness of healthy physical fitness programs on people with intellectual disabilities living in a disability institution: six-month short-term effect.

Little information is available on the provision of physical fitness and intervention program among people with intellectual disabilities. The aim of this study is to provide information of examining the effectiveness of healthy physical fitness programs on people with intellectual disabilities living in a disability institution. There were 146 participants with intellectual disabilities (age 19-67 years) were recruited in the study. We collected information on disability condition (type and level), height, weight, BMI, and physical fitness status (includes V-shape sit and reach test, sit-up 30s, sit-up 60s, and shuttle run) at the beginning and 6 months later of the program intervention. The results show that there were statistical decreases in individual's weight, BMI score, BMI category, and positive improvement in V-shape sit and reach test, sit-up in 30s and 60s tests after 6-month interventions. However, the shuttle run test did not improve at the post-test among people with intellectual disabilities. The results also showed that the mild disability level group has the highest effectiveness on the healthy fitness program on decreasing body weight. Generally speaking, the preliminary study found the healthy exercise program has positive fitness effects on people with intellectual disabilities. To maximize the benefits of regular physical activity on people with ID, there is a need to evaluate the long-term effect of the intervention program and then to initiate the healthy exercise strategies in institution for this group of people.