Related papers: Contrasting Dynamic Spin Susceptibility Models and…
Rings are a model system for studying phase coherence in one dimension. Superconducting rings have states with uniform phase windings that are integer multiples of 2$\pi$ called fluxoid states. When the energy difference between these…
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…
Spin excitations are one of the top candidates for mediating electron pairing in unconventional superconductors. Their coupling to superconductivity is evident in a large number of systems, by the observation of an abrupt redistribution of…
The interplay between superconducting fluctuations (SFs) and weak localization (WL) has been probed by temperature dependent resistance [R(T)] and magnetoresistance (MR) measurements in two-dimensional disordered superconducting TiN thin…
We present a theory for inelastic neutron scattering (INS) and nuclear magnetic resonance (NMR) experiments in the pseudo-gap regime of the underdoped high-$T_c$ cuprates. We show that superconducting phase fluctuations greatly affect the…
We have investigated the spin fluctuations at energy transfers up to ~110 meV, well above the resonance energy (33 meV) in the YBa2Cu3O6.5 ortho-II superconductor using neutron time-of-flight and triple-axis techniques. The spectrum at high…
We report on Monte Carlo studies of the kinetic exchange model for (III,Mn)V ferromagnetic semiconductors in which S=5/2 local moments, representing Mn^{2+} ions, are exchange coupled to band electrons. We treat the Mn^{2+}$ spin…
We study muon-spin rotation (muSR) spectra in the mixed phase of highly anisotropic layered superconductors, specifically Bi_2+xSr_2-xCaCu_2O_8+delta (BSCCO), by modeling the fluid and solid phases of pancake vortices using liquid-state and…
The mechanism of unconventional superconductivity, such as high-temperature-cuprate, Fe-based, and heavy-fermion superconductors, has been studied as a central issue in condensed-matter physics. Spin fluctuations, instead of phonons, are…
Motivated by recent experiments on isovalent-doped 1111 iron-based superconductors LaFeAs$_{1-{x}}$P$_{x}$O$_{1-{y}}$F$_{y}$ and the theoretical study that followed, we investigate, within the five orbital model, the correlation between the…
In this Chapter we review our latest results on magnetic (AC susceptibility) and transport (resistivity) properties of Pr1.85Ce0.15CuO4 (PCCO) and Sm1.85Ce0.15CuO4 (SCCO) thin films grown by pulsed laser deposition technique. Three main…
We report 75As-nuclear quadrupole resonance (NQR) studies on (Ca_4Al_2O_{6-y})(Fe_2As_2) with Tc=27K, which unravel unique normal-state properties and point to unconventional nodeless superconductivity (SC). Measurement of…
We employ the phenomenological Lawrence-Doniach model to compute the contributions of the superconducting fluctuations to the third-harmonic magnetic response, denoted here by $\overline{M_{3}}$, which can be measured in a precise way using…
In several unconventional superconductors, the highest superconducting transition temperature $T_{c}$ is found in a region of the phase diagram where the antiferromagnetic transition temperature extrapolates to zero, signaling a putative…
Inelastic neutron scattering measurements have been performed on single crystals of the heavy fermion compound Ce$_{0.925}$La$_{0.075}$Ru$_{2}$Si$_{2}$ in broad energy [0.1, 9.5 meV] and temperature [40 mK, 294 K] ranges in order to address…
We argue that strongly correlated two dimensional electrons form a spin liquid in some regimes of density and temperature and give the theory of the magnetic properties of this spin liquid using the representation in terms of femions…
We show that it is possible to reconcile NMR and neutron scattering experiments on both LSCO and YBCO, by making use of the Millis-Monien-Pines mean field phenomenological expression for the dynamic spin-spin response function, and…
Nuclear magnetic resonance (NMR) shifts, if stripped off their uncertainties, must hold key information about the electronic fluid in the cuprates. The early shift interpretation that favored a single-fluid scenario will be reviewed, as…
Recent experiments found superconductivity in nonmagnetic MnB$_4$ with a high critical temperature ($T_{c}$) reaching 14 K at 158 GPa. However, ab initio calculations of the electron-phonon coupling predict a $T_{c}$ below 1 K, suggesting…
We argue that the resonant peak observed in neutron scattering experiments on superconducting cuprates and the peak/dip/hump features observed in ARPES measurements are byproducts of the same physical phenomenon. We argue that both are due…