Study of the peak effect phenomenon in single crystals of 2H-NbSe2

Abstract

The weakly pinned single crystals of the hexagonal 2H-NbSe 2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of the peak effect phenomenon in three crystals of 2H-NbSe 2 , in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability effects and pinning.

Quenched metastable vortex states inSr2RuO4

“…The χ ′ SC (H dc ) curve of the FS process has a characteristic peak/dip structure near H c2 . This behavior resembles the peak effect observed in many ordinary type-II superconductors, [7][8][9] and is consistent with previous reports on Sr 2 RuO 4 . [34][35][36]39 The origin of this behavior will be discussed later.…”

“…The ordinary FS branch of Sr 2 RuO 4 exhibits peak/dip structure in χ ′ SC in the field region H * 2 < H dc < H * 3 , similar to the peak effect in ordinary type-II superconductors such as NbSe 2 . 8 The peak effect is attributed to changes in the vortex phases: the low-field onset of the peak effect correspond to the transition between the ordered VBG state in low fields and the disordered VG state, and the peak top corresponds to the transition between the VG and VL states. Therefore, in the ordinary type-II superconductor, H * 2 and H * 3 should correspond to VBG-VG and VG-VL transition lines.…”

“…Such a glassy state has been indeed reported in ordinary type-II superconductors. 8 The second scenario is that a cleaner lattice is formed after a EPFC process. This scenario is based on the fact that the inter-vortex distance only depends on field and cooling process in EPFC should not change the distance.…”

“…also exhibit vortex phase transitions. [7][8][9][10] In such low-T c superconductors, vortices at low fields form a quasi-long-range-ordered lattice, which is called as the vortex Bragg glass (VBG). This is because the arrangement of vortices is mostly governed by the repulsive vortex-vortex interaction.…”

On the nature of superconductivity in the anisotropic dichalcogenide NbSe2{CoCp2}x

“…For NbSe 2 {CoCp 2 } 0.26 the temperature dependency of the in-plane resistivity in various magnetic fields is shown in figure 5(b) in the temperature range between 1.8 K and 8 K. Towards lower temperatures, after the initial steep drop of the resistivity due to the onset of superconductivity, the sample shows a finite resistivity, which again vanishes on further cooling. This observed reentrant behavior is also known from the host sample 2H-NbSe 2 [33]. The out-of-plane resistivity behavior could, however, not be determined, although a special set-up was used as described in [34].…”