Related papers: Quantum vortex core and missing pseudogap in the m…
Ultranarrow superconductors are in the strong quantum confinement regime with formation of multiple coherent condensates associated with the many subbands of the electronic structure. Here we analyze the multiband BCS-BEC crossover induced…
We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface.…
We review the study of the superfluid phase transition in a system of fermions whose interaction can be tuned continuously along the crossover from Bardeen-Cooper-Schrieffer (BCS) superconducting phase to a Bose-Einstein condensate (BEC),…
In contrast to bulk FeSe superconductor, heavily electron-doped FeSe-derived superconductors show relatively high Tc without hole Fermi surfaces and nodal superconducting gap structure, which pose great challenges on pairing theories in the…
Effects of superconducting fluctuation (SCF) on thermodynamic properties of electron systems in the so-called BCS-BEC-crossover regime are studied. As the attractive interaction between electrons becomes stronger upon approaching the…
Superconducting iron chalcogenide FeSe has the simplest crystal structure among all the Fe-based superconductors. Unlike other iron pnictides, FeSe exhibits no long range magnetic order accompanying the tetragonal-to-orthorhombic structural…
Bardeen-Schrieffer-Cooper (BCS) and Bose-Einstein condensation (BEC) occur at opposite limits of a continuum of pairing interaction strength between fermions. A crossover between these limits is readily observed in a cold atomic Fermi gas.…
We investigate strong coupling effects on the superfluid phase transition in a gas of Fermi atoms with a Feshbach resonance. The Feshbach resonance describes a composite quasi-Boson, which can give rise to an additional pairing interaction…
Here we report the electronic structure of FeS, a recently identified iron-based superconductor. Our high-resolution angle-resolved photoemission spectroscopy studies show two hole-like ($\alpha$ and $\beta$) and two electron-like ($\eta$…
The existence of a normal state spectral gap in underdoped cuprates raises important questions about the associated superconducting phase. For example, how does this pseudogap evolve into its below Tc counterpart? In this paper we…
We observed quantum oscillations in thermoelectric and magnetic torque signals in non-centrosymmetric superconductor PbTaSe$_2$. One oscillatory frequency stems from the orbits formed by magnetic breakdown, while others are from…
We present a theory for a superfluid Fermi gas near the BCS-BEC crossover, including pairing fluctuation contributions to the free energy similar to that considered by Nozieres and Schmitt-Rink for the normal phase. In the strong coupling…
We report results of quantum Monte Carlo calculations of the ground state of dilute Fermi gases with attractive short range two-body interactions. The strength of the interaction is varied to study different pairing regimes which are…
Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs…
The symmetry and structure of the superconducting gap in the Fe-based superconductors are the central issue for understanding these novel materials. So far the experimental data and theoretical models have been highly controversial. Some…
The iron-based superconductor FeTe$_{0.55}$Se$_{0.45}$ is a peculiar material: it hosts a surface state with a Dirac dispersion, is a putative topological superconductor hosting Majorana modes in vortices, and has an unusually low Fermi…
Structures and parameters of some high and low temperature superconductors (HTSC, LTSC) are considered basing on the alternative estimate of the O2- ion radius magnitude (0.5-0.6) A. Phase transitions into the superconducting state are…
High-resolution angle-resolved photoemission measurements were taken on FeSe$_{1-x}$S$_x$ (x=0, 0.04, and 0.08) superconductors. With an ultrahigh energy resolution of 0.4 meV, unusual two hole bands near the Brillouin-zone center, which…
We report the study on superconducting pairing mechanism of FeSe via the pair-breaking effects induced by H$^+$-irradiation combined with low-temperature specific heat measurements. A multi-gap structure with nodes or gap minima is…
FeSe is a unique member of the family of iron-based superconductors, not only because of the high values of $T_{c}$ in FeSe monolayer, but also because in bulk FeSe superconductivity emerges inside a nematic phase without competing with…