Predicting diamond-like Co-based chalcogenides as unconventional high temperature superconductors

Abstract

We predict Co-based chalcogenides with a diamond-like structure can host unconventional high temperature superconductivity (high-Tc). The essential electronic physics in these materials stems from the Co layers with each layer being formed by vertex-shared CoA4 (A=S,Se,Te) tetrahedra complexes, a material genome proposed recently by us to host potential unconventional high-Tc close to a d 7 filling configuration in 3d transition metal compounds. We calculate the magnetic ground states of different transition metal compounds with this structure. It is found that (Mn,Fe,Co)-based compounds all have a G-type antiferromagnetic(AFM) insulating ground state while Ni-based compounds are paramagnetic metal. The AFM interaction is the largest in the Co-based compounds as the three t2g orbitals all strongly participate in AFM superexchange interactions. The abrupt quenching of the magnetism from the Co to Ni-based compounds is very similar to those from Fe to Co-based pnictides in which a C-type AFM state appears in the Fe-based ones but vanishes in the Co-based ones. This behavior can be considered as an electronic signature of the high-Tc gene. Upon doping, as we predicted before, this family of Co-based compounds favor a strong d-wave pairing superconducting state.

Cobalt-Dimer Nitrides: A Potential Novel Family of High-Temperature Superconductors

“…The hybridization creates an empty hybridized band at high energy while leaving two near half-filled bands attributed to pure 𝑡 2g orbitals near Fermi energy in the 𝑑 6 configuration of Fe 2+ . We have proposed that the gene condition can be created in a layer formed by corner-shared tetrahedrons, [5,7] in which all three 𝑡 2g 's can be isolated near Fermi energy for the 𝑑 7 configuration of Co 2+ . However, forming such a layer is difficult because of too much energy cost in isolating all three anti-bonding 𝑡 2g orbitals.…”

Pressure-Induced Superconductivity in the Wide-Band-Gap Semiconductor Cu2Br2Se6 with a Robust Framework

“…Transition-metal-based compounds, which include both cuprates and Fe-based superconductors, are exceptionally interesting classes of materials. − Cuprates and Fe-based superconductors have similarities in their structures: whereas cuprates possess two-dimensional (2-D) square CuO 2 planes, Fe-based superconductors are composed of 2-D Fe 2 X 2 (X = Se, As) layers that contain edge-sharing FeX 4 tetrahedra. , The mechanism of superconductivity in both of these classes of unconventional superconductors is still controversial, but it is generally considered to originate from the electron–electron repulsive interaction, which leads to antiferromagnetic fluctuations. , In both families of superconductors, the transition-metal atoms (Cu and Fe) are magnetically ordered in their parent compounds, and the magnetism is suppressed either by chemical doping or by external pressure before superconductivity appears. − Moreover, pressure can enhance the superconducting transition temperatures ( T c s). − These observations have inspired studies of other transition-metal-based chalcogenides under pressure, and a number of unanticipated phenomena, including spin crossover , and superconductivity, , have been observed. Similar to the Fe-based superconductors, the transition-metal cations in most other transition-metal-based chalcogenides are magnetically ordered, − and there are only a few reports of superconductivity in nonmagnetic transition-metal-containing compounds. , …”

BaCuS2: a superconductor with moderate electron-electron correlation

“…Recently, focusing on the d-orbitals, emphasizing electronelectron interaction, we have suggested a new guiding principle for the search of unconventional high T c superconductors: those d-orbitals with d-p σ-bondings must be isolated near Fermi energy. Under this principle, local cation complexes, the connection between the complexes, the electron filling factor at transition metal atoms and lattice symmetries must collaborate to fulfill the criteria [18][19][20][21][22]. This simple principle can explain why cuprates and iron-based superconductors are so special as high T c superconductors.…”