1. State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan, Shandong 250100, People’s Republic of China
2. School of Physics, Shandong University, Jinan, Shandong 250100, People’s Republic of China
3. School of Civil Engineering, Shandong Jiaotong University, Jinan, Shandong 250300, People’s Republic of China