Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session J49: Superconductivity in Infinite-Layer NickelatesInvited Live
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Sponsoring Units: DCMP Chair: George Swatsky, University of British Columbia |
Tuesday, March 16, 2021 3:00PM - 3:36PM Live |
J49.00001: Synthesis and Superconductivity of Infinite-Layer Nickelate Films Invited Speaker: Harold Hwang Since their discovery, superconductivity in cuprates has motivated the search for materials with analogous electronic or atomic structure. We have used soft chemistry approaches to synthesize superconducting infinite layer nickelates from their perovskite precursor phase, using topotactic reactions [1,2]. We will present the synthesis and transport properties of the nickelate superconductors, our current understanding of the electronic structure [3,4], and observation of a doping-dependent superconducting dome in (Nd,Sr)NiO2 [5], similar to cuprates. While cuprate superconductivity is bounded by an insulator for underdoping and a metal for overdoping, here we observe weakly insulating behavior on either side of the dome. Furthermore, the Hall effect suggests the presence of both electron- and hole-like bands, consistent with band structure calculations. Finally, the observation of superconductivity in (Pr,Sr)NiO2 suggests the possibility of a broad family of nickelate superconductors [6]. |
Tuesday, March 16, 2021 3:36PM - 4:12PM Live |
J49.00002: Accessing Experimentally Inaccessible States in Infinite Layer Nickelate Invited Speaker: Kwan-Woo Lee In 2019 H. Hwang and coworkers [Nature 572, 624] discovered superconductivity up to Tc= 15 K in thin film NdNiO2 when hole-doped. This phenomenon is the long sought cuprate-like nickelate superconductity. NdNiO2 (also LaNiO2) with formally Ni1+ ions is isostructural and isovalent with infinite layer CaCuO2 (Cu2+, d9) that superconducts up to 110 K when doped. Two fundamental aspects of the difference between this nickelate and the undoped cuprate give the grand comparison: NdNiO2 is conducting and not magnetically ordered, while undoped cuprate CaCuO2 is insulating and antiferromagnetic (AFM). |
Tuesday, March 16, 2021 4:12PM - 4:48PM Live |
J49.00003: Critical nature of the Ni spin state in doped NdNiO2 Invited Speaker: Mona Berciu Superconductivity with Tc ~ 15K was recently found in doped NdNiO2 , heralding a new family of potentially high-temperature superconductors. According to the Zaanen-Sawatzky-Allen scheme, the Ni1+O2 layers are expected to be Mott insulators, so hole doping should produce Ni2+ with a total spin S=1, which is rather incompatible with robust superconductivity. Using an impurity calculation with a realistic modeling of the O bands, we show that in fact, the NiO2 layers fall inside a critical region where the large pd hybridization favors a singlet 1A1 hole-doped state like in the cuprate high-temperature superconducting layers CuO2. We also find that the superexchange is about one order of magnitude smaller than in cuprates, thus a magnon “glue” is unlikely to be responsible for this superconductivity. |
Tuesday, March 16, 2021 4:48PM - 5:24PM Live |
J49.00004: Doping dependence of superconductivity in infinite layer nickelates Invited Speaker: Ariando Ariando The superconductivity in doped infinite-layer nickelate thin films has hailed another milestone in the field of high-temperature superconductivity. The material processing however remains challenging and the physical understanding of the systems is still in infancy. In this talk, I will present our recent progress in the growth of the nickelate infinite layer superconductors and in the observation of several new exciting properties that can further our understanding of this system. |
Tuesday, March 16, 2021 5:24PM - 6:00PM Live |
J49.00005: Low-valence layered nickelates: a cuprate analog for high-temperature superconductivity? Invited Speaker: Antia Botana The physics behind high-temperature superconductivity in cuprates remains a defining problem in condensed matter physics. Among the myriad approaches to addressing this problem has been the study of alternative transition metal oxides with similar structures and electron count. After a 30 year quest, a non-cuprate compound with a cuprate-like structure that exhibits superconductivity has been found: hole-doped NdNiO2. Given that this material is one of the members of a larger series of layered nickelates, this result opens up the possibility of a new family of unconventional superconductors. By means of first-principles calculations, we have analyzed the similarities and differences between this family of low-valence planar nickelates and cuprates. Even though these nickel oxide materials possess a combination of traits that are widely considered as crucial ingredients for superconductivity in cuprates (a square-planar nature, combined with the appropriate 3d-electron count, and a large orbital polarization) they also exhibit some important differences (a larger p-d energy splitting, and lack of magnetism in the parent compounds). Our results show that low-valence layered nickelates offer a new way of interrogating the cuprate phase diagram and are singularly promising candidates for unconventional superconductivity. |
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