Yan-Ling Xiong(熊艷翎), Jia-Qi Guan(關(guān)佳其), Rui-Feng Wang(汪瑞峰),

Can-Li Song(宋燦立)1,2,?, Xu-Cun Ma(馬旭村)1,2,?, and Qi-Kun Xue(薛其坤)1,2,3,4

1State Key Laboratory of Low-Dimensional Quantum Physics,Department of Physics,Tsinghua University,Beijing 100084,China

2Frontier Science Center for Quantum Information,Beijing 100084,China

3Beijing Academy of Quantum Information Sciences,Beijing 100193,China

4Southern University of Science and Technology,Shenzhen 518055,China

Keywords: pseudogap(PG),modulation doping,Mott insulator,scanning tunneling microscope(STM)

2. Experiment

3. Results and discussion

Another noteworthy feature is a small dip that universally occurs nearEF, circled in Fig. 1(b). To present the feature more clearly,the smaller-energy-scale dI/dVspectra are acquired at the correspondingly identical sites and plotted in Fig. 1(d). A spatially uniform energy gap of approximately 20 meV, irrespective of the existence of Sn vacancy, is identified and symmetric with respect toEF. The results are consistent with the previous findings,except that no apparent van Hove singularity is observable belowEFin our study.[33,34]The robustness of the small energy gap against the Sn vacancy hints at its delocalized nature.

4. Conclusion

Acknowledgments

Project supported by the National Natural Science Foundation of China (Grant Nos. 62074092 and 11604366)and the National Key R&D Program of China (Grant No.2018YFA0305603).