Superconductivity in the vicinity of antiferromagnetic order in CrAs

Wu, Wei; Cheng, Jinguang; Matsubayashi, Kazuyuki; Kong, P. P.; Lin, F. K.; Jin, Changqing; Wang, Naiyan; Uwatoko, Yoshiya; Luo, Jianlin

doi:10.1038/ncomms6508

Cited by 224 publications

(285 citation statements)

References 23 publications

(28 reference statements)

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“…Penetration depth measurements suggest a nodal line in the superconducting gap [6] and a large zero temperature upper critical field H c2 (0) compared to the Pauli limit has been attributed to a spin triplet p-wave pairing [2], in agreement with a theoretical study revealing strong ferromagnetic fluctuations caused by the frustration of Cr moments within one layer [7]. Interestingly, CrAs itself exhibits superconductivity in proximity to a magnetic instability [8]. Moreover, theoretical calculations of the electronic density-of-states indicate a sizable renormalization factor in K 2 Cr 3 As 3 compatible with a large specific heat coefficient [2], suggesting significant electron correlations [9,10].…”

supporting

confidence: 61%

Observation of a Raman-active phonon with Fano line shape in the quasi-one-dimensional superconductorK2Cr3As3

Zhang

Dai

et al. 2015

Phys. Rev. B

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We performed a polarized Raman scattering study of quasi-one-dimensional superconductor K2Cr3As3. We detect two A 1 phonons and three E phonons. One of the A 1 modes exhibits a nearly temperature-independent Fano lineshape. Based on our first-principles calculations, we ascribe this mode to the in-phase vibrations of Cr atoms within one layer. This observation strongly suggests that the magnetic fluctuations in K2Cr3As3 are coupled to the electronic structure via the lattice.PACS numbers: 74.25. Kc, 74.25.nd, 63.20.kd Superconductivity in conventional materials is mediated by the electron-phonon interaction. When the electron-phonon coupling is strong enough, the spectral lineshape of Raman phonon excitations is characterized by an asymmetric profile called Fano lineshape [1]. Despite a superconducting transition temperature (T c ) up to 6.1 K comparable to that of conventional superconductors, the recently discovered quasi-one-dimensional superconductors A 2 Cr 3 As 3 (A = K, Rb, Cs) have exotic properties that tentatively earned them the label of unconventional superconductors [2][3][4], such as an abnormal power law divergence of the 75 As nuclear spin lattice relaxation rate near T c [5]. Penetration depth measurements suggest a nodal line in the superconducting gap [6] and a large zero temperature upper critical field H c2 (0) compared to the Pauli limit has been attributed to a spin triplet p-wave pairing [2], in agreement with a theoretical study revealing strong ferromagnetic fluctuations caused by the frustration of Cr moments within one layer [7]. Interestingly, CrAs itself exhibits superconductivity in proximity to a magnetic instability [8]. Moreover, theoretical calculations of the electronic density-of-states indicate a sizable renormalization factor in K 2 Cr 3 As 3 compatible with a large specific heat coefficient [2], suggesting significant electron correlations [9,10]. However, although some evidences push towards unconventional superconductivity in K 2 Cr 3 As 3 , this view is not universally accepted [11] and whether the electron-phonon interaction plays a key role in this material remains an open question.In this Letter, we report a polarized Raman scattering study of K 2 Cr 3 As 3 . We identify two and three phonon modes with the A 1 and E symmetries, respectively. Surprisingly, one of the A 1 phonons exhibits a Fano lineshape, nearly temperature-independent from 6 K to room temperature, which is characterized by a coupling strength factor 1/q = −0.29. Our theoretical analysis indicates that this mode involves the in-plane movement of the Cr atoms, which directly modulates the Cr-

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supporting

confidence: 61%

Observation of a Raman-active phonon with Fano line shape in the quasi-one-dimensional superconductorK2Cr3As3

Zhang

Dai

et al. 2015

Phys. Rev. B

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“…The present calculated band structure of CrAs at ambient pressure is shown in Fig. S6A, where the Fermi level lies inside the energy band, indicating its metallic characteristics, and is consistent with the experimental results (10). The band scheme of CrAs under ambient and high pressures is shown in Fig.…”

Section: Resultssupporting

confidence: 74%

“…The FeAs planes in binary transition metal monoarsenides (TAs) may serve an analogous role to that served by the CuO plane as a structural proxy for the layered cuprate perovskite family of compounds. These considerations may shed light on the exploration of novel superconductors (10,11). Moreover, CrAs, in which low-lying states near the Fermi level are dominated by 3d electrons, was found to exhibit superconductivity on the verge of antiferromagnetic order via the application of an external high pressure (10).…”

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confidence: 99%

Anomalous anisotropic compression behavior of superconducting CrAs under high pressure

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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CrAs was observed to possess the bulk superconductivity under high-pressure conditions. To understand the superconducting mechanism and explore the correlation between the structure and superconductivity, the high-pressure structural evolution of CrAs was investigated using the angle-dispersive X-ray diffraction (XRD) method. The structure of CrAs remains stable up to 1.8 GPa, whereas the lattice parameters exhibit anomalous compression behaviors. With increasing pressure, the lattice parameters a and c both demonstrate a nonmonotonic change, and the lattice parameter b undergoes a rapid contraction at ∼0.18−0.35 GPa, which suggests that a pressure-induced isostructural phase transition occurs in CrAs. Above the phase transition pressure, the axial compressibilities of CrAs present remarkable anisotropy. A schematic band model was used to address the anomalous compression behavior of CrAs. The present results shed light on the structural and related electronic responses to high pressure, which play a key role toward understanding the superconductivity of CrAs.CrAs | anisotropic compression behavior | high pressure | phase transformation T he discovery of superconductivity (T c = 26 K) in ZrCuSiAstype LaFeAs(O 1−x F x ) (1) inspired extensively experimental and theoretical research on the quaternary "1111" compounds RFeAsO, where R represents a lanthanide (La, Ce, Nd, etc.) (2-5). From the point of view of crystallography, the newly discovered iron-based superconductor exhibits a quasi-2D structural character at ambient conditions. Like the CuO 2 plane in copper oxide high-temperature superconductors, the Fe 2 As 2 layers serve as the conduction planes for charge carriers, and the other building blocks are the charge reservoir layers, dominating the carrier density or the chemical potential. The fundamental structural factors of these compounds are of scientific interest as a meaning of achieving a higher superconducting transition temperature. Previous investigation suggests that the symmetry of the tetrahedral FeAs 4 (6), the FeAs interlayer spacing (7), and the anion (such as As) heights from the iron layer (8, 9) are all crucial aspects of the structure. The FeAs planes in binary transition metal monoarsenides (TAs) may serve an analogous role to that served by the CuO plane as a structural proxy for the layered cuprate perovskite family of compounds. These considerations may shed light on the exploration of novel superconductors (10, 11). Moreover, CrAs, in which low-lying states near the Fermi level are dominated by 3d electrons, was found to exhibit superconductivity on the verge of antiferromagnetic order via the application of an external high pressure (10).Transition-metal-based monoarsenides such as CrAs and MnAs have been extensively studied during the past decades mainly due to their complex magnetism and magnetocaloric effects (12, 13). Furthermore, antiferromagnetic order in FeAs was observed below 70 K (14), whereas the discovery of iron-arsenide-based superconductors has renewed interest in FeAs....

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“…If so, how analogous is this to the resonating valence bond theory [39][40][41] of superconductivity near the Mott insulator? And, is this superconductivity realized in A 2 Cr 3 As 3 (A = K, Rb, Cs) [42] or LiMoO [43,44]?…”

Section: Discussionmentioning

confidence: 99%

Haldane insulator protected by reflection symmetry in the doped Hubbard model on the three-legged ladder

et al. 2016

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We demonstrate the existence of an insulating phase in the three-legged Hubbard ladder at two-thirds filling. In this phase chargons are bound because the physics within a unit cell favors the formation of triplets. The resultant moments lead to a ground state in the Haldane phase, a symmetry protected topological state of matter. In this purely fermionic model, reflection is protecting but time-reversal and dihedral symmetries are not, in contrast to spin models.

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Superconductivity in the vicinity of antiferromagnetic order in CrAs

Cited by 224 publications

References 23 publications

Observation of a Raman-active phonon with Fano line shape in the quasi-one-dimensional superconductorK2Cr3As3

Observation of a Raman-active phonon with Fano line shape in the quasi-one-dimensional superconductorK2Cr3As3

Anomalous anisotropic compression behavior of superconducting CrAs under high pressure

Haldane insulator protected by reflection symmetry in the doped Hubbard model on the three-legged ladder

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