Related papers: Nematic Fluctuations in Iron-Oxychalcogenide Mott …
A site-selective $^{27}$Al nuclear magnetic resonance (NMR) study is carried out on the Kondo lattice compound CePtAl$_4$Ge$_2$, which crystallizes in a rhombohedral lattice with quasi-two-dimensional Ce layers forming a triangular lattice…
Nematicity is ubiquitous in electronic phases of high-$T_c$ superconductors, particularly in the Fe-based systems. While several experiments have probed nematic fluctuations, they have been restricted to uniform or momentum averaged…
Spin subsystem of the copper oxides within the polar Jahn-Teller centers model corresponds to a singlet-triplet magnet where the local boson movement accompanied by the induced longitudinal spin fluctuations. These fluctuations determine…
We show that the neutron scattering spectra observed in CaFe$_2$As$_2$ by Zhao et al (arXiv:0903.2686v1) and the highly unusual spatially anisotropic exchange constants in the iron pnictides derived by Han et al (Phys. Rev. Lett. 102,…
Basic mechanisms controlling orbital order and orbital fluctuations in transition metal oxides are discussed. The lattice driven classical orbital picture, e.g. like in manganites LaMnO$_3$, is contrasted to the quantum behavior of orbitals…
Nematic order often breaks the tetragonal symmetry of iron-based superconductors. It arises from regular structural transition or electronic instability in the normal phase. Here, we report the observation of a nematic superconducting…
Characterizing magnetic fluctuations is one of the keys to understanding the origin of superconductivity in the spin-triplet superconductor UTe$_2$ which exhibits two superconducting (SC) phases (SC1 and SC2) under pressure: SC1 where a…
Electronically-driven nematic order breaks the rotational symmetry of a system, e.g., through a Pomeranchuk instability of the Fermi surface, with a concomitant distortion of the lattice. As a result, in a metal, the nematic collective mode…
We report muon spin relaxation and inelastic neutron measurements on the Heusler system YbPd$_2$Sn. Localised anisotropic and quasi-elastic Yb magnetic fluctuations are observed below $T = 150$K. Both $\mu$SR and neutron data indicate a…
Magnetic fluctuations in an unconventional superconductor (U-SC) can distinguish between distinct proposals for the symmetry of the order parameter. Motivated thereby, we undertake a study magnetic fluctuations in Iron pnictides, tracking…
We report $^{75}$As nuclear magnetic resonance (NMR) studies on a new iron-based superconductor CaKFe$_4$As$_4$ with $T_{\rm c}$ = 35 K. $^{75}$As NMR spectra show two distinct lines corresponding to the As(1) and As(2) sites close to the K…
In the iron pnictide superconductors, two distinct unconventional mechanisms of superconductivity have been put forth: One is mediated by spin fluctuations leading to the s+- state with sign change of superconducting gap between the hole…
We study the pairing mechanism in iron pnictide superconductors based on the five-orbital Hubbard-Holstein model. Due to Fe-ion oscillations, the s-wave superconducting (SC) state without sign reversal (s_{++}-wave state) is induced by…
We study the interplay between superconductivity and antiferromagnetic spin fluctuations in electron-doped cobaltate Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O based on the kinetic energy driven superconductivity mechanism. We show that the…
Understanding the nematic phase observed in the iron-chalcogenide materials is crucial for describing their superconducting pairing. Experiments on FeSe$_{1-x}$S$_x$ showed that one of the slow Shubnikov--de Haas quantum oscillation…
Study of the combined effects of strong electronic correlations with spin-orbit coupling (SOC) represents a central issue in quantum materials research. Predicting emergent properties represents a huge theoretical problem since the presence…
Characterizing non-local magnetic fluctuations in materials with strong electronic Coulomb interactions remains one of the major outstanding challenges of modern condensed matter theory. In this work we address the spatial symmetry and…
A microscopic theory of spin fluctuations of localized electrons interacting with optically cooled nuclear spin bath has been developed. Since nuclear spin temperature may stay low enough for macroscopically long time, the nuclear spin…
TmVO$_4$ exhibits ferroquadrupolar order below 2.15 K with a well-isolated non-Kramers ground state doublet, and is a model system to understand Ising nematic order. We present $^{51}$V nuclear magnetic resonance data as a function of field…
We present inelastic neutron scattering measurements on the intermetallic compounds Ce(Ru$_{1-x}$Fe$_x$)$_2$Ge$_2$ ($x$=0.65, 0.76 and 0.87). These compounds represent samples in a magnetically ordered phase, at a quantum critical point and…