1State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China 2Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 3Songshan Lake Materials Laboratory, Dongguan 523808, China 4School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China 5Frontier Science Center for Quantum Information, Beijing 100084, China
Abstract：We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca$_{3}$Cu$_{2}$O$_{4}$Cl$_{2}$ parent Mott insulator of cuprates. It is found that the upper Hubbard band moves towards the Fermi energy with increasing temperature, while the charge transfer band remains basically unchanged. This leads to a reduction of the charge transfer gap size at high temperatures, and the rate of reduction is much faster than that of conventional semiconductors. Across the Neel temperature for antiferromagnetic order, there is no sudden change in the electronic structure. These results shed new light on the theoretical models about the parent Mott insulator of cuprates.
2022, Vol. 39 
