Related papers: Anomalous High-Energy Electronic Interaction in Ir…
Using ultra-high quality SiGe/Si/SiGe quantum wells at millikelvin temperatures, we experimentally compare the energy-averaged effective mass, $m$, with that at the Fermi level, $m_F$, and verify that the behaviours of these measured values…
The effective attractive interaction between electrons, mediated by electron-phonon coupling, is a well-established mechanism of conventional superconductivity. In metals exhibiting a Fermi surface, the critical temperature of…
Flat electronic bands enable fascinating emergent phenomena such as superconductivity and charge orders. A prevailing approach to realizing flat bands is to engineer lattice geometric constraints in twisted or kagome-like materials. An…
In unconventional superconductors, it is generally believed that understanding the physical properties of the normal state is a pre-requisite for understanding the superconductivity mechanism. In conventional superconductors like niobium or…
The phenomenon of flat bands pinned to the Fermi surface is analyzed on the basis of the Landau-Pitaevskii relation, which is applicable to electron systems of solids. It is shown that the gross properties of normal states of high-$T_c$…
The level of electronic correlation has been one of the key questions in understanding the nature of superconductivity. Among the iron-based superconductors, the iron chalcogenide family exhibits the strongest electron correlations. To…
Electrons can be reflected at an interface between two metals because of a dielectric barrier or different properties of the Fermi surface. Andreev reflection allows to directly measure normal reflection when one of the metals is a…
For the BCS theory of superconductivity, the electron-phonon interaction is transformed to an attractive electron-electron interaction in the vicinity of the Fermi energy only. At the same time, its formal derivation using a unitary…
Iron-based superconductors display a large degree of variability in electronic structure at the Fermi surface, resulting in superconducting gap structures,$T_c$'s, and other properties that vary considerably from family to family. Recently…
The iron chalcogenide Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ on the Te-rich side is known to exhibit the strongest electron correlations among the Fe-based superconductors, and is non-superconducting for $x$ < 0.1. In order to understand the origin…
Electronic correlation effects are manifested in quantum materials when either the onsite Coulomb repulsion is large or the electron kinetic energy is small. The former is the dominant effect in the cuprate superconductors or heavy fermion…
Dirac and Weyl semimetals with linearly crossing bands are the focus of much recent interest in condensed matter physics. Although they host fascinating phenomena, their physics can be understood in terms of weakly interacting electrons. In…
Motivated by the recent discovery of superconductivity in the iron-based ladder compound BaFe$_2$S$_3$ under high pressure, we derive low-energy effective Hamiltonians from first principles. We show that the complex band structure around…
Using \emph{ab initio} band structure and DFT+dynamical mean-field theory methods we examine the effects of electron-electron interactions on the normal state electronic structure, Fermi surface, and magnetic correlations of the recently…
We have shown that the electron transport through junctions of one-dimensional and two-dimensional systems, as well as through quantum point contacts, is considerably affected by the interaction of electrons of different subbands. The…
We consider a multiband metal with deep primary bands and a shallow secondary one. In the normal state the system undergoes Lifshitz transition when the bottom of the shallow band crosses the Fermi level. In the superconducting state Cooper…
The origin of interband electron pairing responsible for enhancing superconductivity and the factors controlling its strength were examined. We show that the interband electron pairing is a natural consequence of breaking down the…
A general theory of superconductivity based on the pairing of electrons that belong to different electronic bands is presented. These electronic bands arise because of a symmetry breaking at the critical temperature in such a way that one…
Motivated by the recent finding of superconductivity in layered CoO_2 compounds, we investigate superconducting and magnetic instabilities of interacting electrons on the two-dimensional triangular lattice. Using a one-loop renormalization…
Electronic interactions in multiorbital systems lead to non-trivial features in the optical spectrum. In iron superconductors the Drude weight is strongly suppressed with hole-doping. We discuss why the common association of the…