Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session U48: Superconductivity: Nickelates II (Theory and Models) |
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Sponsoring Units: DCMP Chair: B. Moritz Room: Mile High Ballroom 1A |
Thursday, March 5, 2020 2:30PM - 2:42PM |
U48.00001: Nickelate superconductivity --Formation of self-doped 2D single-orbital correlated electron systems in NdNiO2 Yusuke Nomura, Motoaki Hirayama, Terumasa Tadano, Yoshihide Yoshimoto, Kazuma Nakamura, Ryotaro Arita The recent discovery of superconductivity in the doped nickelate Nd0.8Sr0.2NiO2 has opened up a great opportunity to unravel the mystery of superconductivity in correlated materials. While the electronic structure of the nickelate is similar to that of the celebrated cuprates, there is one distinct difference: not only the Ni 3dx2-y2 electrons but electrons in the Nd layer also form the Fermi surface. The electronic structure around the Fermi level is well described by the Ni 3dx2-y2, Nd 5d3z2-r2, and a bonding orbital made from the interstitial s and Nd 5dxy orbitals. The hybridization between the Ni 3dx2-y2 and Nd-layer states is small, so that the screening effect of the Nd-layer states is less effective, which leaves the Ni 3dx2-y2 electrons strongly correlated. On the other hand, the electron-phonon coupling constant is not strong enough to mediate superconductivity of Tc~ 10 K. These results indicate that NdNiO2 hosts an almost isolated correlated Ni 3dx2-y2 orbital system with a self-doping due to the Nd-layer-state Fermi pockets [1]. Furthermore, we provide a useful guideline to eliminate the complication due to the self-doping and realize prototypical d9 nickelates [2]. |
Thursday, March 5, 2020 2:42PM - 2:54PM |
U48.00002: Nickelate superconductivity —A systematic computational design of dynamically stable d9 nickelates Motoaki Hirayama, Terumasa Tadano, Yusuke Nomura, Ryotaro Arita The origin of superconductivity in the Sr-doped layered nickelate NdNiO2 has been studied actively since its recent discovery [1]. Several theoretical studies, including our own [2], have shown that the electronic structure of NdNiO2 is quite similar to that of the cuprates near the Fermi level, but they are different in that the Ni 3dx2-y2 orbital is self-doped due to the presence of Fermi pockets formed by the states originating from the Nd block layer (BL). |
Thursday, March 5, 2020 2:54PM - 3:06PM |
U48.00003: Superconductivity in infinite-layer nickelates: similarities and differences from cuprates Antia Botana, Michael Norman The electronic structure of infinite-layer nickelates RNiO2 (R= La, Nd) is revisited in light of the discovery of superconductivity in Sr-doped NdNiO2. From a comparison to their cuprate counterpart CaCuO2, we derive essential facts related to their electronic structures, in particular, the values for hopping parameters and energy splittings, and the influence of the spacer cation. From this detailed comparison, we comment on expectations in regards to superconductivity. In particular, both materials exhibit a large ratio of longer-range hopping to nearest-neighbor hopping which should be conducive for superconductivity. |
Thursday, March 5, 2020 3:06PM - 3:18PM |
U48.00004: Superconductivity in the infinite-layered nickelate (Nd,Sr)NiO2 based on multiorbital model construction Hirofumi Sakakibara, Hidetomo Usui, Katsuhiro Suzuki, Takao Kotani, Hideo Aoki, Kazuhiko Kuroki The striking discovery of superconductivity in an infinite-layered nickelate (Nd,Sr)NiO2[1] has attracted renewed interests in non-copper compounds. The mother compound NdNiO2 has d9 electron configuration as in the high-Tc cuprates, but previous first-principles studies showed that the nickelate has narrower bandwidth than that of the cuprates, and there also exist additional electron-like Fermi pockets originating from the rare-earth 5d orbitals [2,3]. To investigate how these differences affect spin-fluctuation mediated superconductivity, we construct a seven-orbital model consisting of Ni 3d and rare-earth 5d orbitals by employing maximally localized Wannier functions and constrained random phase approximation. We apply fluctuation exchange approximation to the model to evaluate the strength of superconductivity. The calculation has revealed that much larger on-site interaction U than that of the cuprates suppresses Tc of d-wave superconductivity due to strong renormalization effects, while the additional Fermi pockets barely affect Tc [4]. [1] D. Li et al., Nature 572, 624 (2019). [2] V. I. Anisimsov et al., Phys. Rev. B 59, 7901 (1999). [3] K.-W. Lee and W. E. Pickett, Phys. Rev. B 70, 165109 (2004). [4] H. Sakakibara et al., arXiv:1909.00060 (2019). |
Thursday, March 5, 2020 3:18PM - 3:30PM |
U48.00005: Two-band model for magnetism and superconductivity in nickelates Nd1-xSrxNiO2 Lun-Hui Hu, Congjun Wu The recently discovered superconductivity in Nd1-xSrxNiO2 |
Thursday, March 5, 2020 3:30PM - 3:42PM |
U48.00006: d-wave superconductivity in the t−J model with spin one holes: possible applications to the nickelate superconductor Nd1−xSrxNiO2 Yahui Zhang, Ashvin Vishwanath The recent observation of superconductivity at relatively high temperatures in hole doped NdNiO2 has generated considerable interest, particularly due to its similarity with the infinite layer cuprates. Building on the observation that the Ni2+ ions resulting from hole doping are commonly found in the spin-triplet state, we introduce and study a variant of the t−J model in which the holes carry S=1. We find two distinct mechanisms for d wave superconductivity. In both scenarios the pairing is driven by the spin coupling J. However, coherence is gained in distinct ways in these two scenarios. In the first case, the spin-one holes condense leading to a d wave superconductor along with spin-symmetry breaking. In the second scenario, a coherent and symmetric d wave superconductor is achieved from "Kondo resonance": spin one holes contribute two electrons to form large Fermi surface together with the spin 1/2 singly occupied sites. The large Fermi surface then undergoes d wave pairing because of spin coupling J, similar to heavy fermion superconductor.Our study shows that a combination of "cuprate physics" and "heavy fermion physics" may emerge in this novel t−J model. |
Thursday, March 5, 2020 3:42PM - 3:54PM |
U48.00007: Superconductivity in trilayer Nickelates Emilian Nica, Jyoti Krishna, Rong Yu, Qimiao Si, Antia S. Botana, Onur Erten Infinite-layer NdNiO2 has recently been shown to exhibit superconductivity upon Sr-doping [1]. |
Thursday, March 5, 2020 3:54PM - 4:06PM |
U48.00008: Understanding magnetism in infinite-layer nickelates ab initio Victor Pardo, Adolfo O. Fumega, Antia S. Botana Since the discovery of superconductivity in Sr-doped NdNiO2 [1], magnetism has been ruled out [2] as being part of the equation in superconducting layered nickelates. Even though NdNiO2 (containing NiO2 layers with |
Thursday, March 5, 2020 4:06PM - 4:18PM |
U48.00009: Robust dx2−y2 wave superconductivity of infinite-layer nickelates Xianxin Wu, Domenico Di Sante, Tilman Schwemmer, Werner R Hanke, Harold Hwang, Srinivas Raghu, Ronny Thomale Motivated by the recent observation of superconductivity in strontium doped NdNiO2, we study the superconducting instabilities in this system from various vantage points. Starting with first principles calculations, we construct two distinct tight-binding models, a simpler single-orbital as well as a three-orbital model, both of which capture the key low energy degrees of freedom to varying degree of accuracy. We study superconductivity in both models using the random phase approximation (RPA). We then analyze the problem at stronger coupling, and study the dominant pairing instability in the associated t-J model limits. In all instances, the dominant pairing tendency is in the dx2−y2 channel, analogous to the cuprate superconductors. |
Thursday, March 5, 2020 4:18PM - 4:30PM |
U48.00010: Ground States of Infinite-Layer Nickelates at Strong Coupling: A Variational Study Amal Medhi, Chuan Chen, Vijay Shenoy, Debanjan Chowdhury Motivated by the recent discovery of superconductivity in infinite-layer nickelates, we study a two orbital model, including both nickel 3d and the rare-earth 5d orbitals, in the regime of strong local repulsive interactions. Using variational Monte-Carlo calculations which treat strong correlations via suitable projection techniques, we investigate superconductivity and study its dependence on the hole and electron doping, three-dimensionality, and the energetics of the rare-earth 5d orbital. We report a ground state phase diagram of this system, and provide complementary insights using a parton mean-field theory. |
Thursday, March 5, 2020 4:30PM - 4:42PM |
U48.00011: Hole superconductivity in infinite-layer nickelates Frank Marsiglio, Jorge Hirsch We propose that the superconductivity recently observed in Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ with critical temperature in the range $9$ K to $15$ K results from the same charge carriers and the same mechanism that we have proposed give rise to superconductivity in both hole-doped and electron-doped cuprates: pairing of hole carriers in oxygen $p\pi$ orbitals, driven by a correlated hopping term in the effective Hamiltonian that lowers the kinetic energy, as described by the theory of hole superconductivity. We predict a large increase in $T_c$ with compressive epitaxial strain. |
Thursday, March 5, 2020 4:42PM - 4:54PM |
U48.00012: A Determinant Quantum Monte Carlo Study of an Effective Low Energy Model for Infinite-layer Nickelates Fangze Liu, Xuxin Huang, Brian Moritz, Edwin Huang, Thomas Devereaux Our study was motivated by the recent experimental observation of superconductivity in layered nickelate heterostructures with Tc of about 9K to 15K (D Li, et al. 2019). Here, we use determinant quantum Monte Carlo (DQMC) simulations of a composite system, consisting of Hubbard-like Ni, or NiO2, layers coupled to metallic rare-earth layers, to investigate the physics associated with nickelate superconductors. We study the doping-dependent magnetic and electronic properties, such as spin and charge correlations, the single-particle spectral function, interlayer pair correlations, and even superfluid stiffness. |
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