-
Emergence of superconductivity in strongly correlated hole-dominated Fe1-xSe
Authors:
S. L. Ni,
J. P. Sun,
S. B. Liu,
J. Yuan,
Li Yu,
M. W. Ma,
L. Zhang,
L. Pi,
P. Zheng,
P. P. Shen,
D. Li,
D. E. Shi,
G. B. Li,
J. L. Sun,
G. M. Zhang,
K. Jin,
J. -G. Cheng,
F. Zhou,
X. L. Dong,
Z. X. Zhao
Abstract:
Here we establish a more complete phase diagram for FeSe system, based on experimental results of nonstoichiometric Fe1-xSe single crystals that we have developed recently, as well as nearly stoichiometric FeSe single crystals. The electronic correlation is found to be strongly enhanced in hole-dominated Fe1-xSe, as compared with electron-dominated FeSe, from the magnetic susceptibility and electr…
▽ More
Here we establish a more complete phase diagram for FeSe system, based on experimental results of nonstoichiometric Fe1-xSe single crystals that we have developed recently, as well as nearly stoichiometric FeSe single crystals. The electronic correlation is found to be strongly enhanced in hole-dominated Fe1-xSe, as compared with electron-dominated FeSe, from the magnetic susceptibility and electrical transport measurements in the normal state. A superconducting dome is found to emerge starting from the strongly correlated hole-dominated regime with electron doping, while the tetragonal-orthorhombic phase transition at ~90 K is observed only at higher electron-doping levels in the electron-dominated regime.
△ Less
Submitted 29 December, 2019;
originally announced December 2019.
-
Matrix-assisted fabrication and exotic charge mobility of (Li,Fe)OHFeSe superconductor films
Authors:
Y. L. Huang,
Z. P. Feng,
J. Yuan,
W. Hu,
J. Li,
S. L. Ni,
S. B. Liu,
Y. Y. Mao,
H. X. Zhou,
H. B. Wang,
F. Zhou,
G. M. Zhang,
K. Jin,
X. L. Dong,
Z. X. Zhao
Abstract:
Superconducting (Li1-xFex)OHFe1-ySe films are attractive for both the basic research and practical application. However, the conventional vapor deposition techniques are not applicable in synthesizing the films of such a complex system. So no intrinsic charge transport measurements on the films are available so far to reveal the nature of charge carriers, which is fundamental to understanding the…
▽ More
Superconducting (Li1-xFex)OHFe1-ySe films are attractive for both the basic research and practical application. However, the conventional vapor deposition techniques are not applicable in synthesizing the films of such a complex system. So no intrinsic charge transport measurements on the films are available so far to reveal the nature of charge carriers, which is fundamental to understanding the iron-based superconductivity mechanism. Herein we report a soft chemical film technique (matrix-assisted hydrothermal epitaxial growth), by which we have succeeded in growing a series of (Li1-xFex)OHFe1-ySe films covering the whole superconducting regime, with the superconducting transition temperature (Tc) from 4 K up to 42 K. This film technique opens up a new way for fabricating other complex functional materials as well. Furthermore, our systematic transport investigation on the film samples indicates that both the electron and hole carriers contribute to the charge transport, with the scattering rates deviating from the Fermi liquid. We find that the superconductivity occurs upon the electron and hole mobility becoming divergent. And in the high Tc samples, the electron carriers are found much more mobile than the holes, a feature distinct from the low Tc samples. Hence, our transport results provide key insights into the underlying physics for iron-based high-Tc superconductivity.
△ Less
Submitted 8 November, 2017;
originally announced November 2017.
-
First-principles study of the stability of free-standing germanene in oxygen
Authors:
G. Liu,
S. B. Liu,
B. Xu,
C. Y. Ouyang,
H. Y. Song,
X. L. Li
Abstract:
The O2 dissociation and O atoms adsorption on free-standing germanene are studied by using first-principles calculations in this letter. Compared with the spontaneous dissociation of oxygen molecule on free-standing silicene in air, germanene is more stable than silicene from kinetic point of view, with overcoming energy barrier of about 0.55 eV. Especially, in contrast with the unique chemical ad…
▽ More
The O2 dissociation and O atoms adsorption on free-standing germanene are studied by using first-principles calculations in this letter. Compared with the spontaneous dissociation of oxygen molecule on free-standing silicene in air, germanene is more stable than silicene from kinetic point of view, with overcoming energy barrier of about 0.55 eV. Especially, in contrast with the unique chemical adsorption of O2-dissociation-induced O atoms on silicene, oxygen molecule can behave a correspondingly stable adsorption on germanene surface. Moreover, single O atom adsorption on germanene is also different to that on silicene, resulting in two opposite migration pathways on germanene surface. Furthermore, once the oxygen molecule dissociates into O atoms on germanene surface, the migration and desorption of O atoms are relatively difficult under room temperature due to the strong Ge-O bonds in the O-adsorbed germanene, in favor of forming germanium oxides. The results provide compelling evidence to show that free-standing gemanene is relatively stable in oxygen,which is different to silicene essentially.
△ Less
Submitted 16 December, 2014;
originally announced December 2014.