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Chin. Phys. B, 2022, Vol. 31(6): 067401    DOI: 10.1088/1674-1056/ac65f2

Experimental observation of pseudogap in a modulation-doped Mott insulator: Sn/Si(111)-(√30×√30)R30°

Yan-Ling Xiong(熊艳翎)1, Jia-Qi Guan(关佳其)1, Rui-Feng Wang(汪瑞峰)1, Can-Li Song(宋灿立)1,2,†, Xu-Cun Ma(马旭村)1,2,‡, and Qi-Kun Xue(薛其坤)1,2,3,4
1 State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China;
2 Frontier Science Center for Quantum Information, Beijing 100084, China;
3 Beijing Academy of Quantum Information Sciences, Beijing 100193, China;
4 Southern University of Science and Technology, Shenzhen 518055, China
Abstract  Unusual quantum phenomena usually emerge upon doping Mott insulators. Using a molecular beam epitaxy system integrated with cryogenic scanning tunneling microscope, we investigate the electronic structure of a modulation-doped Mott insulator Sn/Si(111)-($\sqrt{3}\times \sqrt{3})R$30$^\circ$. In underdoped regions, we observe a universal pseudogap opening around the Fermi level, which changes little with the applied magnetic field and the occurrence of Sn vacancies. The pseudogap gets smeared out at elevated temperatures and alters in size with the spatial confinement of the Mott insulating phase. Our findings, along with the previously observed superconductivity at a higher doping level, are highly reminiscent of the electronic phase diagram in the doped copper oxide compounds.
Keywords:  pseudogap (PG)      modulation doping      Mott insulator      scanning tunneling microscope (STM)  
Received:  01 March 2022      Revised:  28 March 2022      Accepted manuscript online:  11 April 2022
PACS:  74.72.Kf (Pseudogap regime)  
  81.15.-z (Methods of deposition of films and coatings; film growth and epitaxy)  
  68.37.Ef (Scanning tunneling microscopy (including chemistry induced with STM))  
  68.37.-d (Microscopy of surfaces, interfaces, and thin films)  
Fund: 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).
Corresponding Authors:  Can-Li Song, Xu-Cun Ma     E-mail:;

Cite this article: 

Yan-Ling Xiong(熊艳翎), Jia-Qi Guan(关佳其), Rui-Feng Wang(汪瑞峰), Can-Li Song(宋灿立), Xu-Cun Ma(马旭村), and Qi-Kun Xue(薛其坤) Experimental observation of pseudogap in a modulation-doped Mott insulator: Sn/Si(111)-(√30×√30)R30° 2022 Chin. Phys. B 31 067401

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