Vortex phase diagram in 12442-type RbCa₂Fe₄As₄F₂ single crystal revealed by magneto-transport and magnetization measurements

Abstract

The recently discovered 12442-type ACa2Fe4As4F2 (A = K, Rb, Cs) compounds are the only iron-based superconductors (IBSs) with double FeAs layers between neighboring insulating layers, analogous to the double CuO2 layers in some high-T c cuprates. Here, we report the study of vortex phase diagram of RbCa2Fe4As4F2 single crystal via magneto-transport and magnetization measurements. The resistive transition under magnetic fields shows a foot-like kink at a characteristic temperature, T s, followed by a resistive tail in nearly zero resistivity region. Such behavior is ascribed to a vortex slush transition at T s, below which the vortex state has short-range vortex lattice correlation, and then a second-order transition into the vortex glass phase occurs with further decreasing temperature. Above T s, the Arrhenius plot of resistivity shows two linear regions that are separated by a crossover line T cr(B), which is associated with a crossover from collective to plastic pinning or different flux pinning behaviors resulted from different types of defect. In addition, the magnetic hysteresis loops reveal a second magnetization peak (SMP), which is shifted to lower fields with increasing temperature for T< 12 K. However, the SMP unexpectedly moves back to a higher field at T= 12 K, and then gradually turns into a shoulder or kink that moves to higher fields at high temperatures, such anomalous behavior has never been observed in IBSs. According to the magneto-transport and magnetization data, the vortex phase diagram of RbCa2Fe4As4F2 is finally constructed. Details on the different vortex phase transitions and relevant physical scenarios are given and discussed.

Nodal multigap superconductivity in the anisotropic iron-based compound RbCa2Fe4As4F2

“…Single crystals of RbCa 2 (Fe 1−x Ni x ) 4 As 4 F 2 with x = 0, 0.03 and 0.05 were grown by the self-flux method using RbAs [3,4,26]. The high quality of the investigated single crystals was assessed through X-ray diffraction, energy dispersive X-ray (EDX) spectroscopy and transport measurements, as shown in Fig.…”

Anomalous metallic oxygen band in the potential superconductor KCa$_2$Fe$_4$As$_4$O$_2$

“…The thermal conductivity, resistivity, upper critical field H c2 (T ) of CsCa 2 Fe 4 As 4 F 2 were investigated in [29]. The vortex phase diagram of RbCa2Fe4As4F2 via magneto-transport and magnetization measurements was performed in [30].…”

Effects of Thallium fluoride substitution on the flux pinning energies of (Cu0.5, Tl0.5)Ba2Ca2Cu3O10-δ superconductors

“…The two distinct vortex phases, such as the liquid and glass phases, respectively, determine the normal and superconducting states [7]. Most of the dynamical complexity of the vortices is due to the battle between thermal fluctuations, arbitrary pinning, and the interaction of vortices [8]. At melting temperature, T m , the Abrikosov vortex lattice is a first-order phase transition from a vortex liquid is specified in a pure phase [9][10][11].…”

“…[15]. In pure phases, the slushy vortex phase transition can be conceived of as the remnant of a disordered first-order vortex lattice transition [8,15]. The foregoing discussion has shown that flux pinning has a significant impact on superconductor transport parameters and that the vortex formation in HTSCs having poor pining flux capability is of fundamental relevance [16].…”