Related papers: Charge imbalance in $\lambda$-(BETS)$_2$GaCl$_4$ a…
We report specific heat measurements of the organic superconductors $\kappa$-(ET)$_2$Cu(NCS)$_2$ and $\kappa$-(ET)$_2$Cu[N(CN)$_2$]Br. When the magnetic field is rotated in the highly conducting planes at low temperature ($T\simeq 0.4$ K),…
The relationships among charge order, spin fluctuations, and superconductivity in underdoped cuprates remain controversial. We use neutron scattering techniques to study these phenomena in La$_{1.93}$Sr$_{0.07}$CuO$_4$, a superconductor…
If the topological insulator Bi$_{2}$Se$_{3}$ is doped with electrons, superconductivity with $T_{{\rm c}}\approx3-4\:{\rm K}$ emerges for a low density of carriers ($n\approx10^{20}{\rm cm}^{-3}$) and with a small ratio of the…
Superconductivity in alkali-intercalated iron selenide, with T_c's of 30K and above, may have a different origin than that of the other Fe-based superconductors, since it appears that the Fermi surface does not have any holelike sheets…
Theories of the origin of superconductivity in cuprates are dependent on an understanding of their normal state which exhibits various competing orders. Transport and thermodynamic measurements on La$_{2-x}$Sr$_x$CuO$_4$ show signatures of…
The thermal conductivity of electron-doped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals is investigated below 200K, with an emphasis on the behavior near the magnetic and superconducting (T_c) transition temperatures. An enhancement of…
Electric transport and scanning tunneling spectrum (STS) have been investigated on polycrystalline samples of the new superconductor Bi4O4S3. A weak insulating behavior in the resistive curve has been induced in the normal state when the…
We report hard (14 keV) x-ray diffraction measurements on three compositions (x=0.11,0.12,0.13) of the high-temperature superconductor La2-xSrxCuO4. All samples show charge-density-wave (CDW) order with onset temperatures in the range 51-80…
In quantum materials, charge orders typically stabilize in specific crystallographic orientations, though their formation mechanisms may vary. Here, using low-temperature scanning tunneling microscopy (STM), we discover a lattice-decoupled…
Large pulsed magnetic fields up to 60 Tesla are used to suppress the contribution of superconducting fluctuations (SCF) to the ab-plane conductivity above Tc in a series of YBa2Cu3O(6+x). These experiments allow us to determine the field…
The density of states of the organic superconductor $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br, measured by scanning tunneling spectroscopy on \textit{in-situ} cleaved surfaces, reveals a logarithmic suppression near the Fermi edge persisting…
An intuitive chemical perspective on the LK-99 material is outlined and supported by DFT calculations. A hidden flat Lead band that exhibits instability toward charge density wave formation is exposed. Electron transfer between Lead…
The hole-doped cuprate high temperature superconductors enter the pseudogap regime as their superconducting critical temperature, $T_c$, falls with decreasing hole density. Experiments have probed this regime for over two decades, but we…
The families of organic charge-transfer salts $\kappa$-(BEDT-TTF)$_2X$ and $\kappa$-(BETS)$_2X$ have proven to serve as a powerful playground for the investigation of the physics of frustrated Mott insulators. These materials have been…
We present a combined growth and transport study of superconducting single-crystalline NdO$_{0.5}$F$_{0.5}$BiS$_2$. Evidence of two-dimensional superconductivity with significant phase fluctuations of preformed Cooper pairs preceding the…
The origin of the charge ordering in organic compounds $\theta$-(BEDT-TTF)$_2 X$ ($X=MM'$(SCN)$_4$, $M=$Tl,Rb,Co, $M'=$Cs,Zn) is studied using an extended Hubbard model. Calculating the charge susceptibility within random phase…
The organic charge-transfer salt $\kappa$-(BEDT-TTF)$_{2}$Hg(SCN)$_{2}$Br is a quasi two-dimensional metal with a half-filled conduction band at ambient conditions. When cooled below $T=80$ K it undergoes a pronounced transition to an…
One of the first finding concerning the superconducting (SC) density $n_{\rm sc}$ in cuprates was their small magnitudes that revealed the importance of phase fluctuations. More recently, measurements in a variety of overdoped cuprates…
We analyze the leading vestigial instability due to the melting of a bidirectional pair-density-wave state in two dimensions. In a previous work by one of the authors, it was found that the interplay between pair-density-wave fluctuations…
We report high-resolution specific heat measurements on the quasi-2D organic superconductor $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$, performed by using a most sensitive ac-modulation technique. The main observations are (i) a discontinuity at…