Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session T57: Superconductivity: Mostly NickelatesRecordings Available
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Sponsoring Units: DCMP Chair: Jason Haraldsen, University of North Florida Room: Hyatt Regency Hotel -Clark |
Thursday, March 17, 2022 11:30AM - 11:42AM |
T57.00001: Magnetic, f-electron, and hole doping effects in infinite-layer nickelates Ruiqi Zhang, Christopher A Lane, Bahadur Singh, Johannes S Nokelainen, Matthew Matzelle, Bernardo Barbiellini, Robert S Markiewicz, Arun Bansil, Jianwei Sun Recent discovery of superconductivity in the doped infinite-layer nickelates has renewed interest in understanding the nature of high-temperature superconductivity more generally. The low-energy electronic structure of the parent compound NdNiO2, the role of electronic correlations in driving superconductivity, and the possible relationship between the cuprates and the nickelates are still open questions. Here, by comparing LaNiO2 and NdNiO2 systematically within a parameter-free, first-principles density-functional theory framework, we find the competition between the magnetically ordered phases depends mainly on the gaps in the Ni band. Our estimated value of the on-site Hubbard U in the nickelates is similar to that in the cuprates, but the value of the Hund’s coupling JH is found to be sensitive to the Nd magnetic moment. Moreover, taking LaNiO2 as an example, we find the existence of intertwined low-energy phases with Van Hove singularities contributed by the Ni orbital in both undoped and doped nickelates, which could explain why there are no long-range magnetic orders in nickelates. The hole doping effects are also discussed here. Our findings thus reveal the importance of fluctuating magnetic order in correlated materials. |
Thursday, March 17, 2022 11:42AM - 11:54AM |
T57.00002: A-site Dependence of (R,Sr)NiO2 Superconductivity (R = La, Pr, Nd) Bai Yang Wang, ChunAn Wang, Yu-Te Hsu, Motoki Osada, Kyuho Lee, Chunjing Jia, Danfeng Li, Malcolm R Beasley, Thomas P Devereaux, Nigel E Hussey, Ian R Fisher, Harold Y Hwang Significant efforts in the materials synthesis and experimental characterization of the infinite-layer nickelate superconductors since the initial report [1] have led to a plethora of spectroscopic, microscopic, and magneto-transport observations [2-5]. One of many questions is the role of the lanthanide element located at the corners of the unit cell (A-site) in these observations: whether it is a minor detail or a critical contributor to the superconducting properties. To shed light on this, by conducting a series of angular anisotropy measurements, we investigate side-by-side the A-site dependence of the magneto-transport properties of the infinite-layer nickelate superconductors, based on the recently found A-site variants [6,7]. |
Thursday, March 17, 2022 11:54AM - 12:06PM |
T57.00003: Superconductivity in a minimal two-band model for infinite-layer nickelates Cheng Peng, Hong-Chen Jiang, Brian Moritz, Thomas P Devereaux, Chunjing Jia While the recent discovery of superconductivity in infinite-layer nickelates has drawn considerable attention, a common ingredient of the fundamental building blocks to describe their ground states has been lacking. A series of experimental and theoretical studies have suggested that an effective two-band Hubbard model with Ni 3dx2-y2 and rare-earth (R) 5d character may describe the low-energy physics. We study the ground-state properties of this two-band model on four-leg cylinders using the density-matrix renormalization group (DMRG). At half-filling, the ground state of the system is consistent with a Luttinger liquid, characterized by quasi-long-range charge and spin correlations in the R layer but short-range correlations in the Ni layer. This appears compatible with the experimental observations where electrons in the R layer are responsible for the electron pocket. When the R layer becomes nearly empty and insulating at 12.5% hole doping concentration, our results show that the ground state of the system is consistent with a Luther-Emery liquid, where we find power-law superconducting and charge density correlations in the Ni layer, but exponentially decaying spin correlations. The consistency of our results with experimental observations may help to reveal the microscopic mechanism for pairing in these nickelates and other unconventional superconductors. |
Thursday, March 17, 2022 12:06PM - 12:18PM |
T57.00004: RIXS study on La-based infinite-layer nickelates Wei-Sheng Lee, Matteo Rossi, Motoki Osada, Daniel Jost, Jaewon Choi, Yonghun Lee, Kyuho Lee, Bai Yang Wang, Mirian Garcia-Fernandez, Stefano Agrestini, Zhixun Shen, Brian Moritz, Thomas P Devereaux, Cheng-Tai Kuo, Jun-Sik Lee, Ke-Jin Zhou, Harold Y Hwang The recent discovery of superconducting nickelates has drawn significant interest in the field. Superconductivity was first discovered in the Nd-based infinite-layer nickelates. Soon, superconductivity was confirmed also in the La- and Pr-based infinite layer nickelates. Uncovering how the electronic structure varies between different rare-earth families of compounds could provide further information about the underlying microscopic mechanism. Recently, resonant inelastic x-ray scattering (RIXS) has revealed the electronic and magnetic excitations in the Nd-based infinite-layer nickelates. In this talk, we will present the RIXS results of the La-based infinite-layer nickelates, discuss the underlying elementary excitations, symmetry-broken states, and their comparisons with those in Nd-based compounds. |
Thursday, March 17, 2022 12:18PM - 12:30PM |
T57.00005: Coexistence of ferromagnetism and superconductivity in infinite-layer nickelates Ruby Shi, Bai Yang Wang, Yusuke Iguchi, Motoki Osada, Kyuho Lee, Harold Y Hwang, Kathryn Moler Numerous transport experiments have been performed on the recently discovered infinite-layer superconducting nickelates, yet scanning probe microscopy experiments have been lacking. We use a scanning SQUID (Superconducting QUantum Interference Device) to image surface magnetic response of several superconducting infinite-layer nickelates (RSrNiO2, R = La, Pr, Nd). Both ferromagnetic domains and diamagnetic screening are found to exist in the nickelate thin film. The ferromagnetic domains are attributed to Ni ions. The variation in magnetic signal suggests that an average domain contains thousands of Bohr magnetons, corresponding to an estimated size of a few thousand unit cells. The diamagnetic screening is inhomogeneous and locally suppressed in shapes of lines and crosses along crystal axis. In addition, we find traces of vortices buried under the ferromagnetic background. Our work emphasizes the difference between nickelates and cuprates, suggesting infinite layer nickelates could be a new class of superconductors. |
Thursday, March 17, 2022 12:30PM - 12:42PM |
T57.00006: Role of the interface for superconductivity in infinite-layer nickelate films Berit H Goodge, Benjamin Geisler, Kyuho Lee, Motoki Osada, Bai Yang Wang, Danfeng Li, Harold Y Hwang, Rossitza Pentcheva, Lena F Kourkoutis The stabilization of superconducting infinite-layer nickelates [1] provides a long-awaited experimental platform to explore a close analogue of the high-Tc cuprates. As the family of superconducting nickelate thin films grows [2-4], superconductivity remains unreported in bulk samples, raising questions about the origin of superconductivity in these samples. In particular, the polar interface between the SrTiO3 substrate and RNiO2 (R = rare earth) films has been proposed to host a two-dimensional electron gas (2DEG) with very high carrier density [5]. Leveraging high-resolution electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM), we reveal the atomic-scale lattice structure and charge distribution at the nickelate-substrate interface. Informed by systematically varied theoretical models, we provide a more complete understanding of the role played by this interface for superconductivity. 1. Li, D. et al. Nature 572, 624 (2019) 2. Osada, M. et al. Nano Lett. 20, 5735 (2020). 3. Osada, et al. Advanced Materials, 2104083 (2021). 4. Pan, et al. Nature Materials, in press (2021). 5. Geisler & Pentcheva, Phys. Rev. B 102, 020502 (2020). |
Thursday, March 17, 2022 12:42PM - 12:54PM |
T57.00007: A Look at the Intrinsic Superconducting Phase Diagram of Infinite-Layer Nickelates Kyuho Lee, Motoki Osada, Bai Yang Wang, Berit H Goodge, Yonghun Lee, Woojin Kim, Tiffany Chun-An Wang, Lena F Kourkoutis, Harold Y Hwang The long search for ‘cuprate-analog’ superconductivity in nickel-based oxides has been realized in the superconducting infinite-layer nickelates.1,2 Interestingly, the nickelates display notable distinctions experimentally from the cuprates, particularly in the ground state for non-superconducting doping values.3 Meanwhile, the strong correlation between superconductivity and the magnitude of normal state resistivity,3 along with nontrivial structural defects in this thermodynamically unstable material,4 hints that the established doping dependence study could be affected by extrinsic factors arising from crystalline imperfections. With new advances in sample quality, we have revisited this problem in Nd1–xSrxNiO2 (x = 0~0.3) and have found several important distinctions in the phase diagram compared to our previous investigation.3 The details of the ‘intrinsic’ phase diagram, along with the optimization process of Nd1–xSrxNiO2, will be discussed. |
Thursday, March 17, 2022 12:54PM - 1:06PM |
T57.00008: Evidence for nodal superconductivity in infinite-layer nickelates from penetration depth measurements Shannon Harvey, Bai Yang Wang, Kyuho Lee, Jennifer Fowlie, Motoki Osada, Yonghun Lee, Danfeng Li, Harold Y Hwang Since their discovery in 2019, the infinite-layer nickelates, (A,Sr)NiO2 (A=La, Pr, Nd) have been the subject of robust experimental and theoretical investigation. Determining the pairing symmetry of superconductivity is an important task that will guide theoretical investigations of the pairing mechanism in these materials. Measurements of the London penetration depth can indicate whether the superconducting gap is nodal or not, providing evidence for the pairing symmetry in the material. In this talk, I will present our measurements of the penetration depth for the infinite-layer nickelates across the A-site variants. We use a two-coil mutual inductance technique to measure the penetration depth as a function of magnetic field and temperature, and our results indicate that the infinite-layer nickelates have nodes in their superconducting gap and suggest that they are dirty d-wave superconductors. I will also present results on how their superfluid density changes as a function of chemical doping. |
Thursday, March 17, 2022 1:06PM - 1:18PM |
T57.00009: Synthesis and topotactic transformation of nickelate single-crystals Pascal Puphal, Yu-Mi Wu, Valentin Zimmermann, Katrin Fuersich, Hangoo Lee, Mohammad Pakdaman, Jan A. N. Bruin, Y. Eren Suyolcu, Peter A. van Aken, Jürgen Nuss, Bernhard Keimer, Masahiko Isobe, Matthias Hepting In contrast to the superconducting ground state found in thin films of Sr- or Ca-doped infinite-layer nickelates RNiO2 (R = Pr, Nd, La), polycrystalline powder samples show insulating behavior. Whether epitaxy to a substrate is required for superconductivity in infinite-layer nickelates remains an open question. So far, high-quality bulk single-crystalline samples were not available, although they might host properties distinct from powders. Recently, we therefore synthesized perovskite La1-xCaxNiO3 single-crystals using flux growth under high-pressure (HP) via a Walker-type multi-anvil apparatus. The perovskite crystals were transformed to the infinite-layer phase by topotactic reduction and showed metallic properties, reminiscent of weakly doped thin films. Furthermore, we synthesized perovskite single-crystals with R = Pr and Nd using the HP method as well as optical floating zone growth, which were also reduced towards the infinite-layer phase. We will present details on the synthesis and reduction, together with scanning transmission electron microscopy, x-ray diffraction, magnetic susceptibility, electronic transport, and Raman spectroscopy measurements. |
Thursday, March 17, 2022 1:18PM - 1:30PM |
T57.00010: Pairing symmetry in infinite-layer nickelate superconductors Lin Er Chow, Sujith Kunniniyil Sudheesh, Proloy Nandi, Shengwei Zeng, Zhaoting Zhang, Xiaomeng Du, Zhi Shiuh Lim, Ee Min Elbert Chia, Ariando Ariando The recent success in the fabrication of superconducting nickelate thin film has opened a path to understand the origin of unconventional superconductivity in high-temperature cuprates. However, the challenging material growth, complicated strain and interface effects from the substrate, and a complex multiorbital picture of nickelates have obstructed our understanding on the important physics questions such as the superconducting gap symmetry. Here we perform in-plane London penetration depth measurement on optimally doped (Nd,Sr)NiO2 and (La,Ca)NiO2 to determine the pairing symmetry of the infinite-layer nickelate superconductor family. In contradiction to the cuprate analog picture, our result concretely disproves a dominant dx2-y2-wave pairing symmetry which was predicted in theoretical calculations while suggesting a dominant s-wave pairing with two gaps of different Tc in nickelates. Such observation cannot be convincingly described by the existing theoretical viewpoints and calculations. Our findings could revolutionize understanding of the role of the copper oxide plane and 3dx2-y2 electronic band in the origin of unconventional superconductivity in cuprates. |
Thursday, March 17, 2022 1:30PM - 1:42PM |
T57.00011: Calculation of the phase diagram of nickelate superconductors Motoharu Kitatani, Liang Si, Oleg Janson, Zhicheng Zhong, Paul Worm, Jan M Tomczak, Ryotaro Arita, Karsten Held We calculated the superconducting phase diagram of the recently discovered nickelate superconductors. First, we analyzed the multi-orbital system with a combination of density functional theory (DFT) and dynamical mean field theory (DMFT). We found that the system can be described by a one-band Hubbard model with an additional electron reservoir at least around the superconducting doping region. We then calculated the critical temperature of this simplest model by using the dynamical vertex approximation and obtained a Tc-dome structure centered around 20% Sr-doping, which is in good agreement with subsequent experiments. Within the present framework, the recent experimental results on the effect of strain and pressure can be reasonably understood as the change of tight-binding model parameters (i.e., hoppings and the interaction strength). We further discuss palladates as a possible alternative to nickelates for optimizing these parameters and obtaining a higher-Tc in practice. |
Thursday, March 17, 2022 1:42PM - 1:54PM |
T57.00012: Is there a proximate antiferromagnetic insulating phase in infinite-layer nickelates? Victor Pardo, Harrison LaBollita, Antia S Botana We provide a set of computational experiments based on ab initio calculations to elucidate whether a cuprate-like antiferromagnetic insulating state can be present in the phase diagram of the infinite-layer nickelate family (RNiO2, R= rare-earth). We show that metallicity in the parent phase is produced by an R-d band that requires hybridization with the Ni-d bands to become largely dispersive. If this off-plane R-Ni coupling is suppressed, the system is an antiferromagnetic insulator with an electronic structure closer to the nominal Ni+:d9 occupation since that largely dispersive band becomes much more localized away from the Fermi level. This can be achieved if a structural element that suppresses the c-axis dispersion is introduced (i.e. vacuum in a monolayer of NdNiO2, or a blocking layer in multilayers formed by (NdNiO2)1/(NdNaO2)1). More importantly, we also show how the reduced Ruddlesden-Popper counterparts (e.g. R4Ni3O8) are able to produce the same effect due to the presence of fluorite RO2 blocking slabs |
Thursday, March 17, 2022 1:54PM - 2:06PM |
T57.00013: Dynamical structural instability and a new crystal-electronic structure of superconducting infinite-layer nickelates Hanghui Chen, Chengliang Xia, Yue Chen, Jiaxuan Wu We use first-principles calculations to find that in superconducting infinite-layer nickelates RNiO2, the widely studied tetragonal P4/mmm structure is only dynamically stable for early lanthanide elements R = La-Sm. For late lanthanide elements R = Eu-Lu, an imaginary phonon frequency appears at A = (π, π, π) point. The condensation of this phonon mode into the P4/mmm structure leads to a more energetically favorable I4/mcm structure that is characterized by an out-of-phase rotation of “NiO4 square”. Special attention is given to two borderline cases: PmNiO2 and SmNiO2, in which both the P4/mmm structure and the I4/mcm structure are local minimums, and their energy difference can be tuned via epitaxial strain. Compared to the P4/mmm structure, RNiO2 in the I4/mcm structure has a substantially reduced Ni dx2−y2 bandwidth, a smaller Ni d occupancy, a “cleaner” Fermi surface with less contribution from lanthanide element d orbitals and a decreased critical UNi to stabilize long-range antiferromagnetic ordering. All these features favor Mott physics and render RNiO2 in the I4/mcm structure a closer analogy to superconducting infinite-layer cuprates. |
Thursday, March 17, 2022 2:06PM - 2:18PM |
T57.00014: Superconductivity in infinite-layer Pr0.8Sr0.2NiO2 films on different substrates Qiang Gao, Zhihai Zhu, Xingjiang Zhou, Xiaolin Ren, Hailan Luo This work was supported in part by the National Natural Science Foundation of China (Grant No. 12074411) and (Grant No. 11888101), the National Key Research and Development Program of China (Grant No. 2016YFA0300300 and 2017YFA0302900), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB25000000) and the Research Program of Beijing Academy of Quantum Information Sciences (Grant No. Y18G06). |
Thursday, March 17, 2022 2:18PM - 2:30PM |
T57.00015: Is Nozieres Exhaustion Principle playing a role in the physics of the nickelate superconductors ? Khandker F Quader, Gheorghe L Pascut, Kristjan Haule We perform self-consistent embedded dynamical mean field theory (eDMFT) calculations on LaNiO2 and NdNiO2 across a wide range of temperature (T) and correlation (U). We find evidence that Nozieres Exhaustion Principle (NEP) plays a role in the low-T physics of the nickelates. Below a characteristic T, we find the system to be Fermi liquid (FL) like, where the scattering rate goes to zero as T2, and the Ni-d moments are rapidly getting screened by the conduction electrons. Below the FL temperature, our T-dependent calculation of hybridization and density of states (DOS) show pronounced dip in hybridization below the Fermi level, at the location of the peak in the Ni-d DOS. We suggest that the dip in hybridization arises from insufficient number of conduction electrons needed to fully screen the Ni-d moments, i.e., in essence NEP. This effect pushes down the coherence temperature that signifies full screening. We speculate that superconductivity may be facilitated once there are extra carriers upon doping, thereby increasing the coherence temperature. We also discuss the broader picture that emerges from our calculations as a function of temperature and correlation. |
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