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Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi₃ (A = Sr and Ba).

Shao DF, Luo X, Lu WJ, Hu L, Zhu XD, Song WH, Zhu XB, Sun YP - Sci Rep (2016)

Bottom Line: Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3.SOC suppresses the nesting and stabilizes the structure.ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China.

ABSTRACT
Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi3 (A = Sr and Ba) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling. Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3. SOC suppresses the nesting and stabilizes the structure. Moreover, without SOC the calculation largely underestimates the superconducting transition temperatures (Tc), while with SOC the calculated Tc are very close to those determined by measurements on single crystal samples. The SOC enhanced superconductivity in ABi3 is due to not only the SOC induced phonon softening, but also the SOC related increase of electron-phonon coupling matrix elements. ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.

No MeSH data available.


Related in: MedlinePlus

Structure, resistivity, magnetization, and specific heat characterizations of SrBi3 single crystal.(a) Powder XRD pattern of SrBi3 crushed from many single crystals. The red bars are SrBi3 in PDF card. The inset shows the studied SrBi3 single crystal. (b) Temperature dependence of resistivity of the polished SrBi3 single crystal. The solid line is the Fermi liquid fitting at the low temperature. The inset shows the Bloch-Grneisen-Mott (BGM) model fitting of the resistivity. (c) ZFC and FC magnetic susceptibility of SrBi3 single crystal measured at H = 10 Oe. The superconducting temperature Tc is 5.75 K. The inset shows the magnetic field dependence of magnetization at T = 5 K. (d) Heat capacity of SrBi3 single crystal measured under H = 0 T and H = 5 T. The upper inset shows the  versus T, the solid line is fitting according to . The lower inset shows the  versus T 2.
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f8: Structure, resistivity, magnetization, and specific heat characterizations of SrBi3 single crystal.(a) Powder XRD pattern of SrBi3 crushed from many single crystals. The red bars are SrBi3 in PDF card. The inset shows the studied SrBi3 single crystal. (b) Temperature dependence of resistivity of the polished SrBi3 single crystal. The solid line is the Fermi liquid fitting at the low temperature. The inset shows the Bloch-Grneisen-Mott (BGM) model fitting of the resistivity. (c) ZFC and FC magnetic susceptibility of SrBi3 single crystal measured at H = 10 Oe. The superconducting temperature Tc is 5.75 K. The inset shows the magnetic field dependence of magnetization at T = 5 K. (d) Heat capacity of SrBi3 single crystal measured under H = 0 T and H = 5 T. The upper inset shows the versus T, the solid line is fitting according to . The lower inset shows the versus T 2.

Mentions: As shown in Fig. 8(a), single crystals with a size of 3 × 3 × 2 mm3 were obtained. Powder XRD measurement indicates the good sample quality. The measured temperature dependences of the resistivity (ρ), magnetization (M), and specific heat (Cp) show the superconducting transition at 5.75 K, which is very close to our estimation. Moreover, the electronic specific heatÎ3, which is obtained from the fitting of specific heat based on the relation , shows a value of 10.249 mJ/mol K2. From the relation , using the calculated N(EF) = 2.17 states/eV, we can estimated the electron-phonon coupling parameter λ = 1.005, which is very close to our calculated λ = 1.11. The ratio is higher than the BCS weak-coupling limit of 1.43, which also supports our estimated strong coupling scenario. Other fitted physical parameters are presented in the supplementary material. All the measurements verifies our calculation.


Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi₃ (A = Sr and Ba).

Shao DF, Luo X, Lu WJ, Hu L, Zhu XD, Song WH, Zhu XB, Sun YP - Sci Rep (2016)

Structure, resistivity, magnetization, and specific heat characterizations of SrBi3 single crystal.(a) Powder XRD pattern of SrBi3 crushed from many single crystals. The red bars are SrBi3 in PDF card. The inset shows the studied SrBi3 single crystal. (b) Temperature dependence of resistivity of the polished SrBi3 single crystal. The solid line is the Fermi liquid fitting at the low temperature. The inset shows the Bloch-Grneisen-Mott (BGM) model fitting of the resistivity. (c) ZFC and FC magnetic susceptibility of SrBi3 single crystal measured at H = 10 Oe. The superconducting temperature Tc is 5.75 K. The inset shows the magnetic field dependence of magnetization at T = 5 K. (d) Heat capacity of SrBi3 single crystal measured under H = 0 T and H = 5 T. The upper inset shows the  versus T, the solid line is fitting according to . The lower inset shows the  versus T 2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4759591&req=5

f8: Structure, resistivity, magnetization, and specific heat characterizations of SrBi3 single crystal.(a) Powder XRD pattern of SrBi3 crushed from many single crystals. The red bars are SrBi3 in PDF card. The inset shows the studied SrBi3 single crystal. (b) Temperature dependence of resistivity of the polished SrBi3 single crystal. The solid line is the Fermi liquid fitting at the low temperature. The inset shows the Bloch-Grneisen-Mott (BGM) model fitting of the resistivity. (c) ZFC and FC magnetic susceptibility of SrBi3 single crystal measured at H = 10 Oe. The superconducting temperature Tc is 5.75 K. The inset shows the magnetic field dependence of magnetization at T = 5 K. (d) Heat capacity of SrBi3 single crystal measured under H = 0 T and H = 5 T. The upper inset shows the versus T, the solid line is fitting according to . The lower inset shows the versus T 2.
Mentions: As shown in Fig. 8(a), single crystals with a size of 3 × 3 × 2 mm3 were obtained. Powder XRD measurement indicates the good sample quality. The measured temperature dependences of the resistivity (ρ), magnetization (M), and specific heat (Cp) show the superconducting transition at 5.75 K, which is very close to our estimation. Moreover, the electronic specific heatÎ3, which is obtained from the fitting of specific heat based on the relation , shows a value of 10.249 mJ/mol K2. From the relation , using the calculated N(EF) = 2.17 states/eV, we can estimated the electron-phonon coupling parameter λ = 1.005, which is very close to our calculated λ = 1.11. The ratio is higher than the BCS weak-coupling limit of 1.43, which also supports our estimated strong coupling scenario. Other fitted physical parameters are presented in the supplementary material. All the measurements verifies our calculation.

Bottom Line: Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3.SOC suppresses the nesting and stabilizes the structure.ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China.

ABSTRACT
Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi3 (A = Sr and Ba) by theoretical investigation of the band structures, phonon properties, and electron-phonon coupling. Without SOC, strong Fermi surface nesting leads to phonon instabilities in ABi3. SOC suppresses the nesting and stabilizes the structure. Moreover, without SOC the calculation largely underestimates the superconducting transition temperatures (Tc), while with SOC the calculated Tc are very close to those determined by measurements on single crystal samples. The SOC enhanced superconductivity in ABi3 is due to not only the SOC induced phonon softening, but also the SOC related increase of electron-phonon coupling matrix elements. ABi3 can be potential platforms to construct heterostructure of superconductor/topological insulator to realize topological superconductivity.

No MeSH data available.


Related in: MedlinePlus