Anomalous anisotropic compression behavior of superconducting CrAs under high pressure

Abstract

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....

Quasilinear quantum magnetoresistance in pressure-induced nonsymmorphic superconductor chromium arsenide

“…Figure 3a shows the band structure of CrAs at 14.3 kbar, calculated using the experimental lattice parameters 24 . At the Y point, a band crossing is found at ∼8.6 meV below E F along the k y direction, giving rise to a linear energy–momentum dispersion with a slope ħc .…”

“…This is the 'extreme quantum limit', and it requires the band extrema to be very near the Fermi energy (E F ). Fig 3a shows the band structure of CrAs at 14.3 kbar, calculated using the experimental lattice parameters [23]. For our multiband system, the band structure near the Y point constitutes a promising case for reaching the extreme quantum limit with a standard laboratory field.…”

“…1a) [10]. Using the x-dependence of the unit cell volume in CrAs 1−x P x [23], we estimate that ∆x = 1 corresponds to ∆p ≈ 145 kbar. Therefore, we place CrP at the location of p = 145 kbar relative to CrAs.…”

Lattice dynamics in the double-helix antiferromagnet FeP

“…The overall success of the DFT calculations to capture the lattice dynamics in FeP, as presented in our study, demonstrates that the DFT method may be applicable for investigations of the pressure-induced phenomena in related materials, such as the strong anisotropic compression and isostructural transitions in MnP [15] and CrAs [54]. This may allow one to address the important problem of the pressureinduced superconductivity in these compounds.…”

Research and prospect of CrAs superconductor

“…合肥强磁场中心 [37] 采用了气象传输的方法, 也 另外的进展是磁输运测量, 最近Niu等人 [39] 研究 [34] 表 1 采用不同烧结温度和方法得到不同品质的CrAs单晶 [37] Table 1 Single crystal CrAs grow at different temperatures and conditions [37] 方法 细节 结论 [39] 磁性涨落之间的相互作用.…”