The pseudogap (PG) state and its related intra-unit-cell symmetry breaking remain the focus in the research of cuprate superconductors. Although the nematicity has been studied in Bi2Sr2CaCu2O8+δ, especially underdoped samples, its behavior in other cuprates and different doping regions is still unclear. Here we apply a scanning tunneling microscope to explore an overdoped (Bi, Pb)2Sr2CuO6+δ with a large Fermi surface (FS). The establishment of a nematic order and its real-space distribution is visualized as the energy scale approaches the PG.

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As emerging topological nodal-line semimetals, the family of ZrSiX (X = O, S, Se, Te) has attracted broad interests in condensed matter physics due to their future applications in spintonics.Here, we apply a scanning tunneling microscopy (STM) to study the structural symmetry and electronic topology of ZrSiSe. The glide mirror symmetry is verified by quantifying the lattice structure of the ZrSe bilayer based on bias selective topographies. The quasiparticle interference analysis is used to identify the band structure of ZrSiSe. The nodal line is experimentally determined at ∼ 250 meV above the Fermi level. An extra surface state Dirac point at ∼ 400 meV below the Fermi level is also determined. Our STM measurement provides a direct experimental evidence of the nodal-line state in the family of ZrSiX. arXiv:1801.09979v1 [cond-mat.mtrl-sci]

The electronic evolution of doped Mott insulators has been extensively studied for decades in search of exotic physical phases. The proposed Mott insulator 1T-TaS2 provides an intriguing platform to study the electronic evolution via doping. Here we apply scanning tunneling microscopy (STM) to study the evolution in Ti-doped 1T-TaS2 at different doping levels. The doping Ti atom locally perturbs the electronic and spin state inside the doped star of David and induces a clover-shaped orbital texture at low-doping levels (x < 0.01). The insulator to metal transition occurs around a critical point x = 0.01, in which small metallic and large insulating domains coexist. The clover-shaped orbital texture emerges at a broader energy range, revealing a competition with the electron correlation. It transforms to a disorder-induced Anderson insulating behavior as doping increases. We directly visualize the trapped electrons in dI/dV conductance maps. The comprehensive study of the series of Ti-doped 1T-TaS2 deepens our understanding of the electronic state evolution in a doped strong-correlated system.

Tuning the electronic properties of a matter is of fundamental interest in scientific research as well as in applications. Recently, the Mott insulator-metal transition has been reported in a pristine layered transition metal dichalcogenides 1T -TaS 2 , with the transition triggered by an optical excitation, a gate controlled intercalation, or a voltage pulse. However, the sudden insulatormetal transition hinders an exploration of how the transition evolves. Here, we report the strain as a possible new tuning parameter to induce Mott gap collapse in 1T -TaS 2 . In a strain-rich area, we find a mosaic state with distinct electronic density of states within different domains. In a corrugated surface, we further observe and analyze a smooth evolution from a Mott gap state to a metallic state. Our results shed new lights on the understanding of the insulator-metal transition and promote a controllable strain engineering on the design of switching devices in the future. * yiyin@zju.edu.cn 1 arXiv:2005.13311v2 [cond-mat.str-el] 28 May 2020