Antiferromagnetic fluctuations and a dominant dxyd_{xy}-wave pairing symmetry in nickelate-based superconductors

Motivated by recent experimental studies on superconductivity found in nickelate-based materials, we study the temperature dependence of the spin correlation and the superconducting pairing interaction within an effective two-band Hubbard model by the quantum Monte Carlo method. Based on parameters extracted from first-principles calculations, our intensive numerical results reveal that the pairing with a $d_{xy}$-wave symmetry firmly dominates over other pairings at low temperature, which is mainly determined by the Ni 3$d$ orbital. It is also found that the effective pairing interaction is enhanced as the on-site interaction increases, demonstrating that the superconductivity is driven by strong electron-electron correlation. Even though the $(\pi,\pi)$ antiferromagnetic correlation could be enhanced by electronic interaction, there is no evidence for long-range antiferromagnetic order exhibited in nickelate-based superconductors. Moreover, our results offer possible evidence that the pure electron correlation may not account for the charge density wave state observed in nickelates.Comment: Published versio

Charge Stripe Manipulation of Superconducting Pairing Symmetry Transition

One of the major differences between superconducting cuprates and nickelates is that $d$-wave is dominated in cuprates, while both $s$- and $d$-waves are observed in nickelates. This raises a strong puzzle on its origin, although these two systems exhibit similar structural and electronic characteristics. To solve this puzzle, we have investigated an inhomogeneous Hubbard model on a square lattice using the quantum Monte Carlo method. Surprisingly, we discover that period of charge stripe $\mathcal{P}$, differing in cuprates and nickelates, plays an unexpected role in determining the emergence of distinct pairing symmetries. While the $d$-wave is dominated for $\mathcal{P} \ge 4$ (the cases for cuprates), both $s$- and $d$-wave can appear when $\mathcal{P}< 4$. Taking $\mathcal{P}=3$ as the case for nickelates, we discover that the interplay between hole-doping concentration $\delta$ and charge-stripe amplitude $V_0$ can realize a remarkable $d$-$s$ wave transition. It originates from the $V_0$-modulated charge inhomogeneity between the on-stripe and inter-stripe region, which is stronger in a smaller $\mathcal{P}$ system, forming an interesting selection rule for the preferred pairing symmetry. Interestingly, accompanied by the $d$-$s$ wave transition, there is a novel magnetic-correlation transition, indicating the inherent intercoupling between charge stripe, superconducting pairing, and magnetic correlation. In general, our non-biased simulations provide a new insight into the difference of superconducting pairing mechanism between nickelates and cuprates, highlighting the decisive role of charge stripe.Comment: 5 figures, 7 pages with a supplemen

CDC42-Interacting Protein 4 Gene Is Down Trans-Regulated by HBV DNA polymerase Trans Activated Protein 1.

Hepatitis B Virus (HBV) DNA polymerase transactivated protein 1 (HBVDNAPTP1) is a novel protein transactivated by HBV DNA polymerase, screened by suppression subtractive hybridization technique (GenBank accession no: AY450389). The biological function of HBVDNAPTP1 was investigated in this study.We constructed a vector pcDNA3.1 (-)/myc-His A-HBVDNAPTP1 and used it to transfect acute monocytic leukemia cell line THP-1. HBVDNAPTP1 expression was detected by western blot analysis in the cells. A cDNA library of genes transactivated by HBVDNAPTP1 in THP-1 cells was made in pGEM-T Easy using suppression subtractive hybridization (SSH). The cDNAs were sequenced and analyzed with BLAST search against the sequences in GenBank.Some sequences, such as CIP4, might be involved in apoptosis development. mRNA and protein expression of CIP4 was identified by Real time RT-PCR and western blot in THP-1 cells. HBVDNAPTP1 could down-regulate the expression of CIP4 at both transcription and translation levels.HBVDNAPTP1 may be involved in the positive regulation on the initiation of monocyte apoptosis. The result contribute to reveal the HBVDNAPTP1 biological functions and provide new evidences for further exploration of the regulatory mechanism of HBVDNAPTP1

Unusual Hole-doping-dependent Electronic Instability and Electron-Phonon Coupling in Infinite-layer Nickelates

The interplay between superconductivity and charge density waves (CDWs) under hole doping in cuprates is one of the central phenomena in condensed matter physics. Recently, CDWs are also observed in CaCuO$_2$-analogous nickelates RNiO$_2$ (R = La, Nd) but exhibit fundamentally different hole-doping-dependent behaviors compared to that in cuprates, raising a challenging question on its origin. In this article, we propose that electronic instability (EI) and moment-dependent electron-phonon coupling (MEPC), mainly contributed by Ni 3dx2-y2 and R 5dz2, respectively, may be the possible reasons for CDW formation in RNiO$_2$. Without hole doping, a strong Fermi surface nesting (FSN) induced by the unique feature of van Hove singularity (VHS) across Fermi level exists in RNiO$_2$ but not in CaCuO$_2$, and the unusual temperature-insensitive feature of EI and MEPC could result in rather high temperature CDWs in RNiO$_2$. Under hole doping, the reduced FSN of Ni 3dx2-y2 by the shift of VHS and decreased occupation of R 5dz2 largely weaken EI and MEPC in RNiO$_2$, respectively, suppressing the CDW formation. Our theory not only offers possible explanations to some puzzling experimental observations, but also establishes a unified understanding on the hole-doping-dependent EI and MEPC in nickelates and cuprates