1. State Key Laboratory of New Ceramics and Fine ProcessingSchool of Materials Science and EngineeringTsinghua University Beijing 100084 China
2. MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed MatterSchool of ScienceXi'an Jiaotong University Xi'an 710049 China
3. Department of Physics and Tsinghua‐Foxconn Nanotechnology Research CenterTsinghua University Beijing 100084 China
4. Department of ChemistryTsinghua University Beijing 100084 China