Single crystal growth, transport and scanning tunneling microscopy and spectroscopy of FeSe1−xSx

Single crystals of sulfur-substituted iron selenide, FeSe1−xSx, were grown within eutectics of molten halides, AlCl3/KCl, AlCl3/KCl/NaCl or AlCl3/KBr, under permanent temperature gradient. The innovative “ampoule in ampoule” design of a crystallization vessel allows obtaining mm-sized plate-like sin...

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Bibliographic Details
Published in:CrystEngComm 2018, Vol.20 (17), p.2449-2454
Main Authors: Chareev, Dmitriy, Ovchenkov, Yevgeniy, Shvanskaya, Larisa, Kovalskii, Andrey, Abdel-Hafiez, Mahmoud, Trainer, Dan J, Lechner, Eric M, Iavarone, Maria, Volkova, Olga, Vasiliev, Alexander
Format: Article
Language:English
Subjects:
Aluminum chloride
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Crystal defects
Crystal growth
Crystallization
Fermi surfaces
Halides
Iron
Microscopy
Nematic
Phase transitions
Physical properties
Scanning tunneling microscopy
Single crystals
Sodium chloride
Spectroscopy
Spectrum analysis
Sulfur
Sulfur content
Superconductivity
Temperature gradients
Variations
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Summary:Single crystals of sulfur-substituted iron selenide, FeSe1−xSx, were grown within eutectics of molten halides, AlCl3/KCl, AlCl3/KCl/NaCl or AlCl3/KBr, under permanent temperature gradient. The innovative “ampoule in ampoule” design of a crystallization vessel allows obtaining mm-sized plate-like single crystals with a sulfur content up to x ∼ 0.19. The sharp anomalies in the physical properties indicate the superconducting and nematic phase transitions in FeSe0.96 at TC = 8.4 K and TN = 90 K, respectively. Scanning tunneling microscopy reveals the presence of dumbbell defects associated with Fe vacancies and dark defects at the chalcogen site associated with S within the FeSe1−xSx series of compounds. Scanning tunneling spectroscopy shows the presence of two different superconducting gaps at both hole and electron pockets of the Fermi surface for low S content levels. As a function of sulfur content, TC follows the conventional dome-shaped curve while TN decreases with x. The overall appearance of the T–x phase diagram of FeSe1−xSx suggests the importance of nematic fluctuations for the formation of the superconducting state in these compounds.
ISSN:1466-8033
1466-8033
DOI:10.1039/c8ce00074c