Superconductivity in two-dimensional NbSe₂field effect transistors

Abstract

We describe investigations of superconductivity in few molecular layer NbSe2 field effect transistors. While devices fabricated from NbSe2 flakes less than 8 molecular layers thick did not conduct, thicker flakes were superconducting with an onset that was only slightly depressed from the bulk value for 2H-NbSe2 (7.2K). The resistance typically showed a small, sharp high temperature transition followed by one or more broader transitions which usually ended in a wide tail to zero resistance at low temperatures. We speculate that these multiple resistive transitions are related to disorder in the layer stacking. The behavior of several flakes has been characterized as a function of temperature, applied field and back-gate voltage. We find that the conductance in the normal state and transition temperature depend weakly on the gate voltage, with both conductivity and decreasing as the electron concentration is increased. The application of a perpendicular magnetic field allows the evolution of different resistive transitions to be tracked and values of the zero temperature upper critical field, 2 (0), and coherence length, (0), to be independently estimated. Our results are analyzed in terms of available theories for these phenomena.

Vortex crossing and trapping in doubly connected mesoscopic loops of a single-crystal type-II superconductor

“…Sample A is fully superconducting with an onset transition temperature of T c = 6.3 K, which is only slightly reduced from the bulk value of 7.1 K. The residual resistivity ratio (RRR ≡ R(300 K)/R(8 K)) is 3.3 for this loop, which is typical for this thickness of NbSe 2 , [33,36] indicating the processing did not degrade the quality of the flake. In Figure 2c, we present the magnetoresistance oscillations of Sample A at 1.8 K after removing a smooth background resistance.…”

Strain engineering in semiconducting two-dimensional crystals

“…As shown in Fig. 2(c), low-buckled silicene has nontrivial band reported [11][12][13]. They have not only proven silicene adopting slightly buckled honeycomb geometry and possessing the band dispersion with a behavior analogous to the Dirac cones of graphene, but also synthesized a silicene sheet through epitaxial growth.…”

Recent Advances in Two-Dimensional Materials with Charge Density Waves: Synthesis, Characterization and Applications

“…However, thinner layers of 2D CDW materials, such as 1T-TaS 2 [41,42], 2H-TaS 2 [27], 1T-TaSe 2 [42], 2H-TaSe 2 [31], 2H-NbSe 2 [43] and 1T-TiSe 2 [11], have been reported recently by the mechanical exfoliation technique. Figure 3 shows the first successful exfoliation of a tantalum diselenide (2H-TaSe 2 ) monolayer and a few layers reported by P. Hyziyev et al [31].…”