Pauli-limiting effects in the upper critical fields of a clean LiFeAs single crystal

Khim, Seunghyun; Lee, Bumsung; Kim, Jae Wook; Choi, Eun Sang; Stewart, G. R.; Kim, Kee Hoon

doi:10.1103/physrevb.84.104502

Cited by 106 publications

(109 citation statements)

References 63 publications

(106 reference statements)

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“…Moreover, theoretical works suggest that this phase can exist in the presence of impurities [17][18][19][20][21] and incommensurate spin density waves [22,23], which is consistent with the experimental results [24][25][26][27][28]. Because Fe-based superconductors (FeSC) also have some of these features (they are also layered [29][30][31][32][33][34] clean [35,36] materials with relatively high Maki parameter α ∼ 1−2 [36][37][38][39][40]) we can expect the existence of the FFLO phase [41][42][43].…”

Section: Introductionsupporting

confidence: 77%

Influence of s± symmetry on unconventional superconductivity in pnictides above the Pauli limit – two-band model study

Ptok

2014

Eur. Phys. J. B

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Abstract. The theoretical analysis of the Cooper pair susceptibility shows the two-band Fe-based superconductors (FeSC) to support the existence of the phase with nonzero Cooper pair momentum (called the Fulde-Ferrel-Larkin-Ovchinnikov phase or shortly FFLO), regardless of the order parameter symmetry. Moreover this phase for the FeSC model with s± symmetry is the ground state of the system near the Pauli limit. This article discusses the phase diagram h-T for FeSC in the two-band model and its physical consequences. We compare the results for the superconducting order parameter with s-wave and s±-wave symmetry -in first case the FFLO phase can occur in both bands, while in second case only in one band. We analyze the resulting order parameter in real space -showing that the FeSC with s±-wave symmetry in the Pauli limit have typical properties of one-band systems, such as oscillations of the order parameter in real space with constant amplitude, whereas with s-wave symmetry the oscillations have an amplitude modulation. Discussing the free energy in the superconducting state we show that in absence of orbital effects, the phase transition from the BCS to the FFLO state is always first order, whereas from the FFLO phase to normal state is second order.

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Section: Introductionsupporting

confidence: 77%

Influence of s± symmetry on unconventional superconductivity in pnictides above the Pauli limit – two-band model study

Ptok

2014

Eur. Phys. J. B

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“…This has been reported for organic [35][36][37], cuprate [14,15], pnictide [38][39][40] and heavy fermion [41][42][43] superconductors. Such an overshooting is an important hint in a long standing search for exotic spin-triplet and Fulde-Ferrell-Larkin-Ovchinnikov states (for review see e.g.…”

Section: Introductionmentioning

confidence: 99%

Low anisotropy of the upper critical field in a strongly anisotropic layered cuprateBi2.15Sr1.9CuO6+δ:Evidence for a paramagnetically limited superconductivity

et al. 2014

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We study angular-dependent magnetoresistance in a low Tc layered cuprate Bi2.15Sr1.9CuO 6+δ . The low Tc ∼ 4 K allows complete suppression of superconductivity by modest magnetic fields and facilitate accurate analysis of the upper critical field Hc2. We observe an universal exponential decay of fluctuation conductivity in a broad range of temperatures above Tc and propose a new method for extraction of Hc2(T ) from the scaling analysis of the fluctuation conductivity at T > Tc. Our main result is observation of a surprisingly low Hc2 anisotropy ∼ 2, which is much smaller than the effective mass anisotropy of the material ∼ 300. We show that the anisotropy is decreasing with increasing field and saturates at a small value when the field reaches the paramagnetic limit. We argue that the dramatic discrepancy of high field and low field anisotropies is a clear evidence for paramagnetically limited superconductivity.

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“…γ(T) shows a linear dependence, and valuable information of γ(T) can be obtained over a wide range of temperatures around 9 K with the same 14 T superconducting magnet. γ(T) of x=0.48 is 2.0 for 10 K and that of x=0.75 is 3.0 for 13 K, which are lower than γ =5-8 in the AFe x Se 2 and FeAs1111 system [21,22] but consistent with γ =2-3 in the electron-and hole-doped FeAs122 [14,15,28] and FeAs111 system [31]. γ decreases with decreasing temperature.…”

Section: Temperature Dependence Of the Anisotropy Ratio γ(T)mentioning

confidence: 64%

Upper critical field and superconducting anisotropy of BaFe_2-xRu_xAs₂(x=0.48 and 0.75) single crystals

Jo¹,

Eom²,

Kim³

et al. 2014

Progress in Superconductivity and Cryogenics

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The upper critical field (H c2 ) was determined by applying a magnetic field along the ab plane and c axis for two single crystals of BaFe 2-x Ru x As 2 (x=0.48 and 0.75). The anisotropy of the H c2 (0), γ(0)=H c2 ab (0)/H c2 c (0), was ~1.6 for x=0.48 and ~2.3 for x=0.75. The angle-dependent resistance measured below T c allowed perfect scaling features based on anisotropic Ginzburg-Landau theory, leading to consistent anisotropy values. Because only one fitting parameter γ is used in the scaling for each temperature, the validity of the γ value was compared with that determined from γ=H c2 ab /H c2 c . The γ obtained at a temperature close to T c was 3.0 and decreased to 2.0 at low temperatures. Comparing to the anisotropy determined for electron-or hole-doped BaFe 2 As 2 using the same method, the present results point to consistent anisotropy in Ru-doped BaFe 2 As 2 with other electron-or hole-doped BaFe 2 As 2 .

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Pauli-limiting effects in the upper critical fields of a clean LiFeAs single crystal

Cited by 106 publications

References 63 publications

Influence of s± symmetry on unconventional superconductivity in pnictides above the Pauli limit – two-band model study

Influence of s± symmetry on unconventional superconductivity in pnictides above the Pauli limit – two-band model study

Low anisotropy of the upper critical field in a strongly anisotropic layered cuprateBi2.15Sr1.9CuO6+δ:Evidence for a paramagnetically limited superconductivity

Upper critical field and superconducting anisotropy of BaFe_2-xRu_xAs₂(x=0.48 and 0.75) single crystals

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Pauli-limiting effects in the upper critical fields of a clean LiFeAs single crystal

Cited by 106 publications

References 63 publications

Influence of s± symmetry on unconventional superconductivity in pnictides above the Pauli limit – two-band model study

Influence of s± symmetry on unconventional superconductivity in pnictides above the Pauli limit – two-band model study

Low anisotropy of the upper critical field in a strongly anisotropic layered cuprateBi2.15Sr1.9CuO6+δ:Evidence for a paramagnetically limited superconductivity

Upper critical field and superconducting anisotropy of BaFe2-xRuxAs2(x=0.48 and 0.75) single crystals

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Upper critical field and superconducting anisotropy of BaFe_2-xRu_xAs₂(x=0.48 and 0.75) single crystals