Magnetic topological insulators provide an important materials platform to explore emergent quantum phenomena such as the quantized anomalous Hall (QAH) effect, Majorana modes and the axion insulator state, etc. Recently, MnBi2Te4 was discovered to be the first material realization of a van der Waals (vdW) antiferromagnetic topological insulator (TI). In the two-dimensional (2D) limit, at a record high temperature of 4.5 K, MnBi2Te4 manifests the QAH effect in the forced ferromagnetic state above 12 T. To realize the QAH effect at lower fields, it is essential to search for magnetic TIs with lower saturation fields. By realizing a bulk vdW material MnBi4Te7 with alternating [MnBi2Te4]and [Bi2Te3] layers, we suggest that it is ferromagnetic in plane but antiferromagnetic along the c axis with a small out-of-plane saturation field of ~ 0.22 T at 2 K. Our angle-resolved photoemission spectroscopy and first-principles calculations further demonstrate that MnBi4Te7 is a Z2 antiferromagnetic TI with two types of surface states associated with the [MnBi2Te4] or [Bi2Te3] termination, respectively. Therefore, MnBi4Te7 provides a new material platform to investigate emergent topological phenomena associated with the QAH effect at much lower magnetic fields in its 2D limit.

Solution-processed n-channel organic thin-film transistors (OTFTs) that exhibit a field-effect mobility as high as 11 cm(2) V(-1) s(-1) at room temperature and a band-like temperature dependence of electron mobility are reported. By comparison of solution-processed OTFTs with vacuum-deposited OTFTs of the same organic semiconductor, it is found that grain boundaries are a key factor inhibiting band-like charge transport.

Objectives Studies have reported that rural elders in China have higher levels of depression than their urban peers. We aimed to examine the extent to which four sets of factors (socioeconomic status (SES), healthcare access, health status, social support and participation) account for such rural-urban differences. Methods Cross-sectional data from the 2011 China Health and Retirement Longitudinal Study were analyzed. A representative sample (N = 5,103) of older Chinese (age 60+) was included. Depressive symptoms were measured by the CESD-10. Multilevel linear regression was conducted. Results Rural elders had more depressive symptoms than urban elders. When SES at the individual-, household- and community-level was simultaneously controlled, the rural-urban difference lost its statistical significance. Health status, social support and social participation accounted for some, whereas healthcare access explained almost none, of the rural-urban difference. Discussion Results suggest that SES is the predominant factor accounting for the rural-urban depression gap in China.