Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEffect of Fe excess on structural, magnetic and superconducting properties of single-crystalline Fe(1+x)Te(1-y)Se(y)
163
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Single crystals of Fe(1+x)Te(1-y)Se(y) have been grown with a controlled Fe excess and Se doping, and the crystal structure has been refined for various compositions. The systematic investigation of magnetic and superconducting properties as a function of the structural parameters shows how the material can be driven into various ground states, depending on doping and the structural modifications. Our results prove that the occupation of the additional Fe site, Fe2, enhances the spin localization. By reducing the excess Fe, the antiferromagnetic ordering is weakened, and the superconducting ground state is favored. We have found that both Fe excess and Se doping in synergy determine the properties of the material and an improved 3-dimensional phase diagram is proposed.
rate research
Read More
The idea of employing non-Abelian statistics for error-free quantum computing ignited interest in recent reports of topological surface superconductivity and Majorana zero modes (MZMs) in FeTe$_{0.55}$Se$_{0.45}$. An associated puzzle is that the topological features and superconducting properties are not observed uniformly across the sample surface. Understanding and practical control of these electronic inhomogeneities present a prominent challenge for potential applications. Here, we combine neutron scattering, scanning angle-resolved photoemission spectroscopy (ARPES), and microprobe composition and resistivity measurements to characterize the electronic state of Fe$_{1+y}$Te$_{1-x}$Se$_{x}$. We establish a phase diagram in which the superconductivity is observed only at sufficiently low Fe concentration, in association with distinct antiferromagnetic correlations, while the coexisting topological surface state occurs only at sufficiently high Te concentration. We find that FeTe$_{0.55}$Se$_{0.45}$ is located very close to both phase boundaries, which explains the inhomogeneity of superconducting and topological states. Our results demonstrate the compositional control required for use of topological MZMs in practical applications.
We use bulk magnetic susceptibility, electronic specific heat, and neutron scattering to study structural and magnetic phase transitions in Fe$_{1+y}$Se% $_x$Te$_{1-x}$. Fe$_{1.068}$Te exhibits a first order phase transition near 67 K with a tetragonal to monoclinic structural transition and simultaneously develops a collinear antiferromagnetic (AF) order responsible for the entropy change across the transition. Systematic studies of FeSe$%_{1-x}$Te$_x$ system reveal that the AF structure and lattice distortion in these materials are different from those of FeAs-based pnictides. These results call into question the conclusions of present density functional calculations, where FeSe$_{1-x}$Te$_x$ and FeAs-based pnictides are expected to have similar Fermi surfaces and therefore the same spin-density-wave AF order.
Neutron scattering has played a significant role in characterizing magnetic and structural correlations in Fe$_{1+y}$Te$_{1-x}$Se$_x$ and their connections with superconductivity. Here we review several key aspects of the physics of iron chalcogenide superconductors where neutron studies played a key role. These topics include the phase diagram of Fe$_{1+y}$Te$_{1-x}$Se$_{x}$, where the doping-dependence of structural transitions can be understood from a mapping to the anisotropic random field Ising model. We then discuss orbital-selective Mott physics in the Fe chalcogenide series, where temperature-dependent magnetism in the parent material provided one of the earliest cases for orbital-selective correlation effects in a Hunds metal. Finally, we elaborate on the character of local magnetic correlations revealed by neutron scattering, its dependence on temperature and composition, and the connections to nematicity and superconductivity.
Superconductivity (SC) with the suppression of long-range antiferromagnetic (AFM) order is observed in the parent compounds of both iron-based and cuprate superconductors. The AFM wave vectors are bicollinear ($pi$, 0) in the parent compound FeTe different from the collinear AFM order ($pi$, $pi$) in most iron pnictides. Study of the phase diagram of Fe$_{1+y}$Te$_{1-x}$Se$_x$ is the most direct way to investigate the competition between bicollinear AFM and SC. However, presence of interstitial Fe affects both magnetism and SC of Fe$_{1+y}$Te$_{1-x}$Se$_x$, which hinders the establishment of the real phase diagram. Here, we report the comparison of doping-temperature ($x$-$T$) phase diagrams for Fe$_{1+y}$Te$_{1-x}$Se$_x$ (0 $leq$ $x$ $leq$ 0.43) single crystals before and after removing interstitial Fe. Without interstitial Fe, the AFM state survives only for $x$ $<$ 0.05, and bulk SC emerges from $x$ = 0.05, and does not coexist with the AFM state. The previously reported spin glass state, and the coexistence of AFM and SC may be originated from the effect of the interstitial Fe. The phase diagram of Fe$_{1+y}$Te$_{1-x}$Se$_x$ is found to be similar to the case of the 1111 system such as LaFeAsO$_{1-x}$F$_x$, and is different from that of the 122 system.
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 of such behaviors, we have performed ARPES studies of Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ ($x$ = 0, 0.1, 0.2, and 0.4). The obtained mass renormalization factors for different energy bands are qualitatively consistent with DFT + DMFT calculations. Our results provide evidence for strong orbital dependence of mass renormalization, and systematic data which help us to resolve inconsistencies with other experimental data. The unusually strong orbital dependence of mass renormalization in Te-rich Fe$_{1+y}$Te$_{1-x}$Se$_{x}$ arises from the dominant contribution to the Fermi surface of the $d_{xy}$ band, which is the most strongly correlated and may contribute to the suppression of superconductivity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
