Abstract:The discovery of superconductivity in thin films (∼10 nm) of infinite-layer hole-doped NdNiO2 has invigorated the field of high temperature superconductivity research, reviving the debate over contrasting views that nickelates that are isostructural with cuprates are either 1) sisters of the high temperature superconductors, or 2) that differences between nickel and copper at equal band filling should be the focus of attention. Each viewpoint has its merits, and each has its limitations, suggesting that such a… Show more
“…However, the challenge in the fabrication of high-quality infinite-layer nickelate films obstructed the experimental means to investigate, especially with those surface-sensitive techniques are not applicable when bad crystallinity or secondary phases are prone to form at the surface of nickelate superconducting thin-film [25]. Overall, while the discovery of superconductivity in the nickelate provided an exciting playground to study the highly correlated system, the newfound superconductor family also ignited controversial debates that will reshape high-T c framework [4][5][6][30][31][32][33][34][35][36][37]. In this article, we provided a contemporary experimental perspective on the topics.…”
After the reward of more than 2 decades of pursuit on the high-Tc cuprate analog with the hope to obtain a better understanding of the mechanism of high-Tc superconductivity, the discovery of superconductivity in the infinite-layer nickelate brings more mystery to the picture than expected. Tops in the list of questions are perhaps 1) absence of superconductivity in the bulk nickelate and limited thickness of the infinite-layer phase in thin film, 2) absence of superconductivity in the La-nickelate despite it being the earliest studied rare-earth nickelate, and the role of 4 f orbital in the recipe of superconductivity, 3) absence of Meissner effect and suspect of the origin of superconductivity from the interface, 4) whether nickelate hosts similar pairing symmetry to the single-band high-Tc cuprates or multiband iron-based superconductor. In this perspective article, we will discuss the following aspects: 1) stabilization of the infinite-layer phase on the SrTiO3(001) substrate and the thickness dependency of observables; 2) rare-earth dependence of the superconducting dome and phase diagram of the (La/Pr/Nd)- infinite-layer nickelate thin film; 3) experimental aspects of the measurement of Meissner effect; 4) theoretical framework and experimental study of the pairing symmetry of infinite-layer nickelate superconductor.
“…However, the challenge in the fabrication of high-quality infinite-layer nickelate films obstructed the experimental means to investigate, especially with those surface-sensitive techniques are not applicable when bad crystallinity or secondary phases are prone to form at the surface of nickelate superconducting thin-film [25]. Overall, while the discovery of superconductivity in the nickelate provided an exciting playground to study the highly correlated system, the newfound superconductor family also ignited controversial debates that will reshape high-T c framework [4][5][6][30][31][32][33][34][35][36][37]. In this article, we provided a contemporary experimental perspective on the topics.…”
After the reward of more than 2 decades of pursuit on the high-Tc cuprate analog with the hope to obtain a better understanding of the mechanism of high-Tc superconductivity, the discovery of superconductivity in the infinite-layer nickelate brings more mystery to the picture than expected. Tops in the list of questions are perhaps 1) absence of superconductivity in the bulk nickelate and limited thickness of the infinite-layer phase in thin film, 2) absence of superconductivity in the La-nickelate despite it being the earliest studied rare-earth nickelate, and the role of 4 f orbital in the recipe of superconductivity, 3) absence of Meissner effect and suspect of the origin of superconductivity from the interface, 4) whether nickelate hosts similar pairing symmetry to the single-band high-Tc cuprates or multiband iron-based superconductor. In this perspective article, we will discuss the following aspects: 1) stabilization of the infinite-layer phase on the SrTiO3(001) substrate and the thickness dependency of observables; 2) rare-earth dependence of the superconducting dome and phase diagram of the (La/Pr/Nd)- infinite-layer nickelate thin film; 3) experimental aspects of the measurement of Meissner effect; 4) theoretical framework and experimental study of the pairing symmetry of infinite-layer nickelate superconductor.
“…La- d bands start appearing above 1 eV (only one spin channel is analyzed for clarity). The O- p bands start to emerge below -3 eV in this case, further away from the Fermi level than in the cuprates 10 , 47 . Figure 5 Top panel.…”
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 low-valence layered nickelate family (R$$_{n+1}$$
n
+
1
Ni$$_n$$
n
O$$_{2n+2}$$
2
n
+
2
, R= rare-earth, $$n=1-\infty$$
n
=
1
-
∞
) in proximity to half-filling. It is well established that at $$d^9$$
d
9
filling the infinite-layer ($$n=\infty$$
n
=
∞
) nickelate is metallic, in contrast to cuprates wherein an antiferromagnetic insulator is expected. We show that for the Ruddlesden-Popper (RP) reduced phases of the series (finite n) an antiferromagnetic insulating ground state can naturally be obtained instead at $$d^9$$
d
9
filling, due to the spacer RO$$_2$$
2
fluorite slabs present in their structure that block the c-axis dispersion. In the $$n=\infty$$
n
=
∞
nickelate, the same type of solution can be derived if the off-plane R-Ni coupling is suppressed. We show how this can be achieved if a structural element that cuts off the c-axis dispersion is introduced (i.e. vacuum in a monolayer of RNiO$$_2$$
2
, or a blocking layer in multilayers formed by (RNiO$$_2$$
2
)$$_1$$
1
/(RNaO$$_2$$
2
)$$_1$$
1
).
“…La-d bands start appearing above 1 eV (only one spin channel is analyzed for clarity). The O-p bands start to emerge below -3 eV in this case, further away from the Fermi level than in the cuprates 9,35 .…”
Section: Turning Infinite Layer Nickelates Into Antiferromagnetic Ins...mentioning
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 low-valence layered nickelate family (Rn+1NinO2n+2, R= rare-earth, n = 1 − ∞) in proximity to half-filling. It is well established that at d9 filling the infinite-layer (n = ∞) nickelate is metallic, in contrast to cuprates wherein an antiferromagnetic insulator is expected. We show that for the Ruddlesden-Popper (RP) reduced phases of the series (finite n) an antiferromagnetic insulating ground state can naturally be obtained instead at d9 filling, due to the spacer RO2 fluorite slabs present in their structure that block the c-axis dispersion. In the n = ∞ nickelate, the same type of solution can be derived if the off-plane R-Ni coupling is suppressed. We show how this can be achieved if a structural element that cuts off the c-axis dispersion is introduced (i.e. vacuum in a monolayer of RNiO2, or a blocking layer in multilayers formed by (RNiO2)1/(RNaO2)1).
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