Lower critical field, anisotropy, and two-gap features of LiFeAs

Sasmal, Kalyan; Lv, Bing; Tang, Zhongjia; Wei, Fengyan; Xue, Y. Y.; Guloy, Arnold M.; Chu, C. W.

doi:10.1103/physrevb.81.144512

Cited by 50 publications

(53 citation statements)

References 28 publications

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“…Here, G denotes the full propagator and Q is the quadratic part of the action (131). The left-hand side of the n-th order Ward-identity then simply consists of a sum over n differences where γ (2n) with q added to the i-th ingoing leg is subtracted from γ (2n) with −q added to the i-th outgoing leg.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, it seems commonly accepted that the superconducting gap is nodeless as confirmed by a large body of experimental results like NMR [130], specific heat [131], ARPES [132] and penetration depth measurements [133,134]. In order to explore these different ordering tendencies, the FRG formalism allows to employ a combined approach of density functional theory (DFT) and FRG which connects an ab initio description with the unbiased analysis of functional RG.…”

Section: P-based Compoundsmentioning

confidence: 99%

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Functional renormalization group for multi-orbital Fermi surface instabilities

Platt

Hanke

Thomale

2013

Advances in Physics

194

253

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Technological progress in material synthesis, as well as artificial realization of condensed matter scenarios via ultra-cold atomic gases in optical lattices or epitaxial growth of thin films, is opening the gate to investigate a plethora of unprecedented strongly correlated electron systems. In a large subclass thereof, a metallic state of layered electrons undergoes an ordering transition below some temperature into unconventional states of matter driven by electronic correlations, such as magnetism, superconductivity, or other Fermi surface instabilities. While this type of phenomena has been a well-established direction of research in condensed matter for decades, the variety of today's accessible scenarios pose fundamental new challenges to describe them. A core complication is the multi-orbital nature of the low-energy electronic structure of these systems, such as the multi-d orbital nature of electrons in iron pnictides and transition-metal oxides in general, but also electronic states of matter on lattices with multiple sites per unit cell such as the honeycomb or kagome lattice. In this review, we propagate the functional renormalization group (FRG) as a suited approach to investigate multi-orbital Fermi surface instabilities. The primary goal of the review is to describe the FRG in explicit detail and render it accessible to everyone both at a technical and intuitive level. Summarizing recent progress in the field of multi-orbital Fermi surface instabilities, we illustrate how the unbiased fashion by which the FRG treats all kinds of ordering tendencies guarantees an adequate description of electronic phase diagrams and often allows to obtain parameter trends of sufficient accuracy to make qualitative predictions for experiments. This review includes detailed and illustrative illustrations of magnetism and, in particular, superconductivity for the iron pnictides from the viewpoint of FRG. Furthermore, it discusses candidate scenarios for topological bulk singlet superconductivity and exotic particle-hole condensates on hexagonal lattices such as sodium-doped cobaltates, graphene doped to van Hove filling, and the kagome Hubbard model. In total, the FRG promises to be one of the most versatile and revealing numerical approaches to address unconventional Fermi surface instabilities in future fields of condensed matter research.

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Section: Resultsmentioning

confidence: 99%

Section: P-based Compoundsmentioning

confidence: 99%

Functional renormalization group for multi-orbital Fermi surface instabilities

Platt

Hanke

Thomale

2013

Advances in Physics

194

253

View full text Add to dashboard Cite

show abstract

“…The data can be reasonably fit with the S-wave two-gap α model with the T c and the zero-temperature diamagnetic moment M 0 as the additional fitting parameters. 13 The data of other samples are then scaled against this reference, i.e., presented as M SC /M 0 vs T /T c to match this scaled reference. It should be pointed out that the data actually represent the supercurrent's circulating individual vortex, i.e., within a length scale ≈20 nm at 5 T. The scaling factor M 0 , in addition, should lead to the supercarrier density if no drastic changes in the gap structure occur with the doping.…”

Section: -T Diamagnetizationmentioning

confidence: 99%

“…14 At higher fields, the differential susceptibility 4π dM/dH drops almost linearly with H based on Bean's model until approaching a rather small reversible moment of (1) after the full penetration. 13 The slope 4π d 2 M/dH 2 will be proportional to the respective critical current density. The penetration depth and the corresponding critical current density in the three stages are usually very different.…”

Section: Low-field 4πχ Zfcmentioning

confidence: 99%

Doping dependence of phase-separation morphology in (Sr,K)Fe2As2

Wei

Chen

et al. 2011

Phys. Rev. B

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The effects of the possible phase separation on macroscopic transport properties are explored in (Sr,K)Fe 2 As 2 . Three probes, the low-field shielding 4πχ ZFC , the reversible diamagnetization M SC at 5 T, and the specific heat C p , with different characteristic length scales on the order of 10 3 , 10, and 10 0 nm, respectively, were used to examine several (Sr 1−x K x )Fe 2 As 2 samples. The data from different probes should be consistent if the sample can be regarded as mesoscopically homogeneous. While this seems to be the case for the optimally doped x = 0.45 samples, the apparent transition temperature and the effective superfluid density strongly depend on the probes used for both the underdoped (x = 0.3) and the overdoped (x = 0.7) samples. Discrepancies of up to a factor of 10 are observed. The data further suggest that both the x = 0.3 and x = 0.7 samples are better described as Josephson-junction arrays formed over separated superconductive domains of 10−10 2 nm sizes. Such a morphology evolution may drastically affect the interpretation of the observed doping effects.

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“…experiments. 9,[34][35][36][37][38][39][40][41][42][43][44] Because various experimental results show different anisotropies for given compounds, we collected all the available experimental results and represent them as the error bar. We assume that the upper critical field anisotropy γ H C2 = H C2 ab /H C2 c is same to γ λ .…”

mentioning

confidence: 99%

Small anisotropy in iron-based superconductors induced by electron correlation

Lee

Shim

2011

Phys. Rev. B

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We have investigated the electron correlation effect on the electronic structures and transport properties of the iron-based superconductors using density functional theory (DFT) and dynamical mean field theory (DMFT). By considering the Fe 3d electron correlation using DMFT, the quasiparticle bandwidth near the Fermi level is found to be substantially suppressed compared to the conventional DFT calculation. Because of the different renormalization factors of each 3d orbital, DMFT gives considerably reduced electrical anisotropy compared to DFT results, which explains the unusually small anisotropic resistivity and superconducting property observed in the iron-based superconductors. We suggest that the electron correlation effect should be considered to explain the anisotropic transport properties of the general d/f valence electron system. Discovery of [superconducting transition temperature (T c )] high-T c superconductivity (HTSC) in LaFeAsO 1−x F x with T c = 26 K 1 has stimulated the effort to understand the mechanism of HTSC and search for new materials with this property. Similar to the well-known cuprate superconductors, it has a layered structure with the square lattice of transition metals, and the superconductivity emerges from the boundary of the antiferromagnetic ordering of 3d valence electrons. This indicates that the magnetic ordering, or more likely its fluctuation, is closely related to the electron pairing both in cuprate and iron-based superconductors. Since the first discovery, many subsequent iron-based superconductors have been reported coming from the parent compounds of ReFeAsOF (Re: rare earth elements), AeFe 2 As 2 (Ae: Ba, Sr, and Ca), LiFeAs, FeSe, 2-6 etc. All the superconductors have similar crystal structures and electronic properties. Twodimensional FeAs (or FeSe) layers are commonly observed to be sandwiched by the insulating blocking layers, which induces the anisotropic electronic structures. In all the compounds, multiple Fe 3d orbitals participate in the magnetic or superconducting transitions. Because of the numerous investigations on iron-based superconductors, one could use many available experimental data of their physical properties for the comparative study of these materials in clarifying the origin of HTSC.Anisotropy is an important parameter with which to understand the mechanism of the HTSC. Usually the low dimensionality has been believed to be the crucial factor for increasing the superconducting T c . Most of the compounds with HTSC have layered structure, and the maximum T c among the cuprate superconductors is designed from highly anisotropic compounds. Indeed, density functional theory (DFT) calculations predict two-dimensional electronic structures and anisotropic transport properties of the iron-based superconductors.7 Using the same strategy as that applied to the cuprate superconductors, researchers have tried to synthesize highly anisotropic iron-base superconductors such as Sr 2 VO 3 Fe 2 As 2 with a blocking layer of Sr 2 VO 3 . 6 However, the observed...

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Lower critical field, anisotropy, and two-gap features of LiFeAs

Cited by 50 publications

References 28 publications

Functional renormalization group for multi-orbital Fermi surface instabilities

Functional renormalization group for multi-orbital Fermi surface instabilities

Doping dependence of phase-separation morphology in (Sr,K)Fe2As2

Small anisotropy in iron-based superconductors induced by electron correlation

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