Research
High-Tc Superconductors
1. Cuprate Superconductors
I. M. Vishik. Rep. Prog. Phys. 81, 062501 (2018)
• Fermi surface reconstruction in NCCO- • Electronic supermodulation in YBCO
- • Coexistence of two sharp-mode couplings in Bi2212
The cuprate high-Tc superconductors have inspired intense research interest since their discovery in 1986. A wealth of advances, including the synthesis of high-quality samples, innovations in experimental techniques and the development of theoretical models have been motivated by the research in cuprates. These advances, in turn, have deepened our understanding of the cuprates system. However, a unified understanding of the cuprate superconductors, including both the superconducting mechanism and the normal state properties, remains to be reached. Our previous highlights in cuprates are summarized below:
2. Iron-based Superconductors
Hideo Aoki and Hideo Hosono. Phys. World 28 (2), 31 (2015)- • Interface enhanced 2D high Tc superconductors - FeSe/STO
- • Single-layer FeSe/STO film
The discovery of superconductivity in iron pnictides in 2008 ignited an explosion of research activities that uncovered a new family of high-Tc superconductors. As the second player in the field of high-Tc superconductivity, iron-based superconductors have already demonstrated a complexity comparable to that of the cuprates. They also provide us with a second route to explore the mechanism of high-Tc superconductivity. Summaries of our previous highlights in iron-based superconductors are shown below:
• Insulator–superconductor crossover in single-layer FeSe/SrTiO3 films
• Dichotomy of the electronic structure and superconductivity between single-layer and double-layer FeSe/SrTiO3 films
3. Nickelate Superconductors
Yu Miao, et al., arXiv:2608.03908
Nickelate superconductors have recently emerged as a new class of unconventional high-temperature superconductors. The discovery of superconductivity near 80 K in bilayer La3Ni2O7 single crystals under pressures above ~14 GPa established layered nickelates as genuine high-Tc systems. Complementing studies of bulk crystals, recent advances in epitaxial thin films have opened new opportunities to realize and tune high-Tc superconductivity at ambient pressure. Compressively strained La3Ni2O7 and (La,Pr)3Ni2O7 films exhibit superconducting onset above 40 K, while optimized (La,Pr)3Ni2O7 films have now reached onset temperatures of above 60 K at ambient pressure. These advances make bilayer nickelate films a particularly promising platform for investigating the microscopic pairing mechanism and for engineering still higher transition temperatures. Our previous highlights in nickelate superconductors are listed below:
• Nodeless superconducting gap and electron-boson coupling in (La,Pr,Sm)3Ni2O7 films
• Thermodynamic phase transition, pairing symmetry and Fermi surface topology in Ruddlesden-Popper nickelate films
• Electronic structures across superconductor-insulator transition in Ruddlesden-Popper bilayer nickelate films
• Thermodynamic phase transition, pairing symmetry and Fermi surface topology in Ruddlesden-Popper nickelate films
• Electronic structures across superconductor-insulator transition in Ruddlesden-Popper bilayer nickelate films
Kagome Superconductors
Kagome metal has become an important platform to study the interplay among electron correlation, band topology and lattice geometry. Its unique lattice structure formed by corner-sharing triangles exhibits Dirac cones, Van Hove singularities and electronic flat band, which may induce exotic topological quantum phenomena such as charge density wave and unconventional superconductivity. The recent discovered quasi two-dimensional layered Kagome superconductor displays three-dimensional charge order, nematic order, pairing density wave and Z2 topological surface state which has attracted a lot of research interest. Our previous highlights in Kagome metal are listed below:
• Realizing Kagome Band Structure in Surface States of RV6Sn6 (R = Gd, Ho)
• Topological surface states and flat bands in CsV3Sb5
• Electronic states dressed by an out-of-plane supermodulation in CsV3Sb5
B. R. Ortiz et al., Phys. Rev. Lett. 125, 247002 (2020)
Spin-orbit Coupled Mott Insulators
B. J. Kim et al., Phys. Rev. Lett. 101, 076402 (2008)
Perovskite iridates represent the 5d-electron counterpart of cuprates, in which the cooperation of spin-orbit coupling and Coulomb interactions gives rise to a Mott insulating state. Many exotic quantum phenomena appear when the spin-orbit-coupled Mott insulators are doped with carriers. Summaries of our previous highlights in iridates can be found below:
• Electron-boson coupling in electron-doped Sr2IrO4
• Negative electronic compressibility in (Sr1-xLax)3Ir2O7
• Fermi arcs vs. Fermi pockets in (Sr1-xLax)3Ir2O7