Fully gapped superconducting state in Au2Pb: a natural candidate for topological superconductor

We measured the ultra-low-temperature specific heat and thermal conductivity of Au$_2$Pb single crystal, a possible three-dimensional Dirac semimetal with a superconducting transition temperature $T_c \approx$ 1.05 K. The electronic specific heat can be fitted by a two-band s-wave model, which gives the gap amplitudes $\Delta_1$(0)/$k_BT_c$ = 1.38 and $\Delta_2$(0)/$k_BT_c$ = 5.25. From the thermal conductivity measurements, a negligible residual linear term $\kappa_0/T$ in zero field and a slow field dependence of $\kappa_0/T$ at low field are obtained. These results suggest that Au$_2$Pb has a fully gapped superconducting state in the bulk, which is a necessary condition for topological superconductor if Au$_2$Pb is indeed one.Comment: 6 pages, 4 figure

Governing cross-border regions: History, characteristics, and implications from the European Union

The recent development of globalization and regionalization has witnessed the emergence of a new form of regional governance-cross-border cooperation.The European Union hosts some of the most representative cross-border regions and provides good examples of cross-border region-building.In this paper, we review the institutionalization process of cross-border cooperation in the EU (formerly European Community), focusing on how multilevel governance was structured and how relevant policy packages were formulated and played out on the ground.Based on key actors involved in and main characteristics of cross-border institutionalization, we divide the process of cross-border cooperation into four phases: initiation (characterized by cross-border spatial planning), growth (characterized by cross-border legal frameworks), expansion (characterized by INTERREG initiatives) and deepened cooperation (characterized by the EU Cohesion Policy and multilevel governance).Spatial, legal, and economic issues were the priorities of different phases, leaving national sovereignty as the main hurdle for further institutional integration.Drawing on the lessons from the EU and the observations in the Yangtze River Delta, we made several suggestions on how the Yangtze River Delta would build its own cross-boundary regions.Although regions in the Yangtze River Delta are not separated by hard borders and are thus free from most political issues faced by EU cross-border regions, they encountered many spatial, economic, and institutional issues in regional development that are similar to EU cross-border regions.We, therefore, suggest a couple of aspects that they can learn from the EU cross-border development, including the establishment of project-based cooperation platforms supported by stable funding, the inclusion of multiple stakeholders in multilevel governance, particularly grassroots governments and cross-boundary organizations, and the promotion of cooperation between adjacent regions.We hope these suggestions would further contribute to the development of regional cooperation in China, which may extend from cross-boundary cooperation between neighbors to multifaceted cooperation and multilevel governance