arXiv subjects

Yuhao Gu

Publications and source records attributed to Yuhao Gu.

23 records · Page 2Linked to original sources

arXiv2020

A substantial hybridization between correlated Ni-d orbital and itinerant electrons in infinite-layer nickelates

The discovery of unconventional superconductivity in hole doped NdNiO2, similar to CaCuO2, has received enormous attention. However, different from CaCuO2, RNiO2 (R = Nd, La) has itinerant electrons in the rare-earth spacer layer. Previous studies show that the hybridization between Ni-dx2-y2 and rare-earth-d orbitals is very weak and thus RNiO2 is still a promising analog of CaCuO2. Here, we perform first-principles calculations to show that the hybridization between Ni-dx2-y2 orbital and itinerant electrons in RNiO2 is substantially stronger than previously thought. The dominant hybridization comes from an interstitial-s orbital rather than rare-earth-d orbitals, due to a large inter-cell hopping. Because of the hybridization, Ni local moment is screened by itinerant electrons and the critical U_Ni for long-range magnetic ordering is increased. Our work shows that the electronic structure of RNiO2 is distinct from CaCuO2, implying that the observed superconductivity in infinite-layer nickelates does not emerge from a doped Mott insulator.

cond-mat.str-el↗

arXiv2020

Unconventional High Temperature Superconductivity in Cubic Zinc-blende Transition Metal Compounds

We consider possible high temperature superconductivity (high-T$_c$) in transition metal compounds with a cubic zinc-blende lattice structure. When the electron filling configuration in the d-shell is close to d$^7$, all three t$_{2g}$ orbitals are near half filling with strong nearest neighbor antiferromagnetic (AFM) superexchange interactions. We argue that upon doping, this electronic environment can be one of "genes" to host unconventional high T$_c$ with a time reversal symmetry broken $d_{2z^2-x^2-y^2} \pm i d_{x^2-y^2}$ pairing symmetry. With gappless nodal points along the diagonal directions, this state is a direct three dimensional analogue to the two dimensional $B_{1g}$ d-wave state in cuprates. We suggest that such a case may be realized in electron doped CoN, such as CoN$_{1-x}$O$_x$ and (H, Li)$_{1-x}$CoN.

cond-mat.supr-con↗

arXiv2019

Topological superconductivity in Ni-based transition-metal trichalcogenide superconductors

Based on a two-orbital honeycomb lattice model and random phase approximation, we investigate the pairing symmetry of the Ni-based transition-metal trichalcogenide. We find that an I-wave (A2g) state and a chiral d-wave state are dominant and nearly degenerate for typical electron and hole dopings. These two states carry nontrivial topological properties, which are manifested by the presence of chiral edge states in the d+id-wave state and dispersionless Andreev bound state at zero energy in the I-wave state. Ni-based transition-metal trichalcogenides provide us a new platform to study the exotic phenomena emerged from electron-electron correlation effects.

cond-mat.supr-con↗

arXiv2018

Ni-based transition-metal trichalcogenide monolayer: a strongly correlated quadruple-layer graphene

We investigate the electronic physics of layered Ni-based trichalcogenide NiPX$_3$ (X=S, Se), a member of transition-metal trichalcogenides (TMTs) with the chemical formula, ABX$_3$. These Ni-based TMTs distinguish themselves from other TMTs as their low energy electronic physics can be effectively described by the two $e_g$ d-orbitals. The major band kinematics is characterized by the unusal long-range effective hopping between two third nearest-neighbor (TNN) Ni sites in the two-dimensional Ni honeycomb lattice so that the Ni lattice can be equivalently viewed as four weakly coupled honeycomb sublattices. Within each sublattice, the electronic physics is described by a strongly correlated two-orbital graphene-type model that results in an antiferromagnetic (AFM) ground state near half filling. We show that the low energy physics in a paramagnetic state is determined by the eight Dirac cones which locate at $K$, $K'$, $\frac{K}{2}$ and $\frac{K'}{2}$ points in the first Brillouin zone with a strong AFM fluctuation between two $K (K')$ and $\frac{K'}{2} (\frac{K}{2})$ Dirac cones and carrier doping can sufficiently suppress the long-range AFM order and allow other competing orders, such as superconductivity, to emerge. The material can be an ideal system to study many exotic phenomena emerged from strong electron-electron correlation, including a potential $d\pm id$ superconducting state at high temperature.

cond-mat.str-el↗

arXiv2018

Predicting Diamond-like Co-based Chalcogenides as Unconventional High Temperature Superconductors

We predict Co-based chalcogenides with a diamond-like structure can host unconventional high temperature superconductivity (high-$T_c$). The essential electronic physics in these materials stems from the Co layers with each layer being formed by vertex-shared CoA$_4$ (A=S,Se,Te) tetrahedra complexes, a material genome proposed recently by us to host potential unconventional high-$T_c$ 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 $t_{2g}$ 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-$T_c$ gene. Upon doping, as we predicted before, this family of Co-based compounds favor a strong d-wave pairing superconducting state.

cond-mat.supr-con↗