Glassy Dynamics in a heavy ion irradiated NbSe2 crystal

Abstract

Fascination with glassy states has persisted since Fisher introduced the vortex-glass as a new thermodynamic phase that is a true superconductor that lacks conventional long-range order. Though Fisher’s original model considered point disorder, it was later predicted that columnar defects (CDs) could also induce glassiness — specifically, a Bose-glass phase. In YBa2Cu3O7−x (YBCO), glassy states can cause distinct behavior in the temperature (T ) dependent rate of thermally activated vortex motion (S). The vortex-glass state produces a plateau in S(T ) whereas a Bose-glass can transition into a state hosting vortex excitations called double-kinks that can expand, creating a large peak in S(T ). Although glass phases have been well-studied in YBCO, few studies exist of other materials containing CDs that could contribute to distinguishing universal behavior. Here, we report on the effectiveness of CDs tilted ~30° from the c-axis in reducing S in a NbSe2 crystal. The magnetization is 5 times higher and S is minimized when the field is parallel to the defects versus aligned with the c-axis. We see signatures of glassiness in both field orientations, but do not observe a peak in S(T ) nor a plateau at values observed in YBCO. Finally, we discuss the possibility that competing disorder induces a field-orientation-driven transition from a Bose-glass to an anisotropic glass involving both point and columnar disorder.

Experimental test of strong pinning and creep in current-voltage characteristics of type-II superconductors

“…Fitting the data of 2H-NbSe 2 for T = 4.8 K yields the barrier U c ≈ 980 K, see Fig. 4, a value that is consistent with the observed creep rate [31] ranging from S ≈ 5 × 10 −3 to S ≈ 10 −2 .…”

A precursor mechanism triggering the second magnetization peak phenomenon in superconducting materials

“…The minimum in the S(H) curves is associated with the lowest creep activity of vortices inside the sample and it has been already observed along with the presence of the SMP phenomenon 17 , 18 , 20 , 22 , 47 , although their correlation still presents a puzzling challenge. For this purpose, the S(H) curve at T = 2.5 K has been plotted together with the J c (H) curve at the same temperature in order to search for correlation between the creep rate and the SMP phenomenon.…”

Peak Effects in 2H-NbSe2 Single Crystals Introduced with Artificial Defects by Particle Irradiation

“…The anomalous peak effect is usually observed in magnetization measurements and the peak field locates approximately equals to 1/3 B Φ (B Φ : dose equivalent matching field) [1,7]. Recently, a similar peak effect located at ~1/5 B Φ was reported in NbSe 2 introduced with tilted columnar defects by 1.4 GeV Pb irradiation [8]. On the other hand, other peak effects which are located at around H c2 are frequently [9,10].…”