“…This is associated with the fact that high pressure brings the layers in the unit cell closer together, and facilitates overlap of wave functions of the conduction electrons in the adjacent layers. The T c (6.64 K) of Cr 0.0005 NbSe 2 is found to be less than undoped NbSe 2 single crystal, and similar trend has been reported for various intercalated compounds Fe x NbSe 2 6,38 , NbSe 2 36,40 , Ga x NbSe 2 11 , Pd x NbSe 2 45 , Cu x NbSe 2 12 , (LaSe) 1.14 (NbSe 2 ) 46 pnictides 34,44 at both ambient and pressure.Figure 1( a ) Temperature dependent of resistivity at various applied hydrostatic pressures from 0 to 8 GPa, ( b ) pressure evolution of onset ( T c onset ) and offset ( T c offset ) superconducting transition temperature from resistivity measurements c) temperature dependent of zero field cooled (ZFC) [closed symbols] and field cooled (FC) [open symbols] dc magnetization at various hydrostatic pressures from 0 to 1.02 GPa.…”
Section: Resultssupporting
confidence: 80%
“…Niobium diselenide (NbSe 2 ) is one of the most studied layered TMDs which has van der Waals attraction between the layers and it has generated much attention due to interplay of superconducting transition temperature ( T c ) 4–7 and T CDW 2,8–10 is around 7 K and 33 K respectively. Anisotropy in TMDs, particularly in NbSe 2 compounds, having the highest T c among TMDs, could be significantly enhanced by introducing foreign atoms or molecules in the interlayer space (intercalation process) 6,9,11,12 . The intercalation ability of these compounds is related to the expected implementation of high temperature superconductivity in the sandwich type structures described by the excitonic mechanism 6,9,13 .…”
Section: Introductionmentioning
confidence: 99%
“…The intercalation ability of these compounds is related to the expected implementation of high temperature superconductivity in the sandwich type structures described by the excitonic mechanism 6,9,13 . Further remarkably, Zeeman-protected Ising superconductivity is expected in NbSe 2 due to non-centrosymmetric structure with in-plane inversion symmetry breaking and strong spin-orbit coupling and the anomalous large in-plane critical magnetic field has become one important direction in crystalline 2D superconductors 11,12,14,15 . The vortex movement (i.e., vortex entry into or exit from a single-crystalline superconductor) is possibly pinned at the edges when applied very low magnetic field which can be generally attributed to the translational symmetry breaking at the edges and it is dependent on both shape and dimension of the superconductors 13,16 .…”
Superconducting properties of Cr0.0005NbSe2 (Tc~6.64 K) single crystals have been investigated through the temperature dependent resistivity (~8 GPa) and DC magnetization (~1 GPa) measurements. Further, the critical current density (Jc) as a function of applied magnetic field has been studied from magnetic isotherms. The vortex pinning mechanisms have also been systematically analyzed using weak collective pinning theory as a function of pressure. The Jc corresponds to the flux flow enhanced by the application of pressure due to increase of Tc and vortex changes. We found that the pressure is responsible for the spatial variations in the charge carrier mean free path (δl pinning). We find that core point pinning is more dominant than surface pinning which is caused by the application of pressure. In addition, Jc(H = 0) increases from 3.9 × 105 (0 GPa) to 1.3 × 106 (1.02 GPa) A/cm2 at 2 K as the pressure is increased from normal pressure to 1.02 GPa. The pressure dependence of Tc (dTc/dP) becomes 0.91 K/GPa and 0.75 K/GPa from magnetization and resistivity measurements respectively. We found that the pressure promotes the anisotropy nature, and decrease of coherence length and resulting in pathetic interface of the vortex core with pinning centers.
“…This is associated with the fact that high pressure brings the layers in the unit cell closer together, and facilitates overlap of wave functions of the conduction electrons in the adjacent layers. The T c (6.64 K) of Cr 0.0005 NbSe 2 is found to be less than undoped NbSe 2 single crystal, and similar trend has been reported for various intercalated compounds Fe x NbSe 2 6,38 , NbSe 2 36,40 , Ga x NbSe 2 11 , Pd x NbSe 2 45 , Cu x NbSe 2 12 , (LaSe) 1.14 (NbSe 2 ) 46 pnictides 34,44 at both ambient and pressure.Figure 1( a ) Temperature dependent of resistivity at various applied hydrostatic pressures from 0 to 8 GPa, ( b ) pressure evolution of onset ( T c onset ) and offset ( T c offset ) superconducting transition temperature from resistivity measurements c) temperature dependent of zero field cooled (ZFC) [closed symbols] and field cooled (FC) [open symbols] dc magnetization at various hydrostatic pressures from 0 to 1.02 GPa.…”
Section: Resultssupporting
confidence: 80%
“…Niobium diselenide (NbSe 2 ) is one of the most studied layered TMDs which has van der Waals attraction between the layers and it has generated much attention due to interplay of superconducting transition temperature ( T c ) 4–7 and T CDW 2,8–10 is around 7 K and 33 K respectively. Anisotropy in TMDs, particularly in NbSe 2 compounds, having the highest T c among TMDs, could be significantly enhanced by introducing foreign atoms or molecules in the interlayer space (intercalation process) 6,9,11,12 . The intercalation ability of these compounds is related to the expected implementation of high temperature superconductivity in the sandwich type structures described by the excitonic mechanism 6,9,13 .…”
Section: Introductionmentioning
confidence: 99%
“…The intercalation ability of these compounds is related to the expected implementation of high temperature superconductivity in the sandwich type structures described by the excitonic mechanism 6,9,13 . Further remarkably, Zeeman-protected Ising superconductivity is expected in NbSe 2 due to non-centrosymmetric structure with in-plane inversion symmetry breaking and strong spin-orbit coupling and the anomalous large in-plane critical magnetic field has become one important direction in crystalline 2D superconductors 11,12,14,15 . The vortex movement (i.e., vortex entry into or exit from a single-crystalline superconductor) is possibly pinned at the edges when applied very low magnetic field which can be generally attributed to the translational symmetry breaking at the edges and it is dependent on both shape and dimension of the superconductors 13,16 .…”
Superconducting properties of Cr0.0005NbSe2 (Tc~6.64 K) single crystals have been investigated through the temperature dependent resistivity (~8 GPa) and DC magnetization (~1 GPa) measurements. Further, the critical current density (Jc) as a function of applied magnetic field has been studied from magnetic isotherms. The vortex pinning mechanisms have also been systematically analyzed using weak collective pinning theory as a function of pressure. The Jc corresponds to the flux flow enhanced by the application of pressure due to increase of Tc and vortex changes. We found that the pressure is responsible for the spatial variations in the charge carrier mean free path (δl pinning). We find that core point pinning is more dominant than surface pinning which is caused by the application of pressure. In addition, Jc(H = 0) increases from 3.9 × 105 (0 GPa) to 1.3 × 106 (1.02 GPa) A/cm2 at 2 K as the pressure is increased from normal pressure to 1.02 GPa. The pressure dependence of Tc (dTc/dP) becomes 0.91 K/GPa and 0.75 K/GPa from magnetization and resistivity measurements respectively. We found that the pressure promotes the anisotropy nature, and decrease of coherence length and resulting in pathetic interface of the vortex core with pinning centers.
“…4) suggest similar phonon spectra, indicating that these are not the main cause of the strong differences in the T c values. Such a strong reduction of T c for the ferecrystals compared to the MLCs cannot be explained by the in-plane polycrystallinity of the NbSe 2 layers either, as the transition temperature for polycrystalline NbSe 2 has been reported to be identical37. A reduction of T c by less than 2.5% due to polycrystallinity is reported for NbSe 2 single crystals3738.…”
Hybrid electronic heterostructure films of semi- and superconducting layers possess very different properties from their bulk counterparts. Here, we demonstrate superconductivity in ferecrystals: turbostratically disordered atomic-scale layered structures of single-, bi- and trilayers of NbSe2 separated by PbSe layers. The turbostratic (orientation) disorder between individual layers does not destroy superconductivity. Our method of fabricating artificial sequences of atomic-scale 2D layers, structurally independent of their neighbours in the growth direction, opens up new possibilities of stacking arbitrary numbers of hybrid layers which are not available otherwise, because epitaxial strain is avoided. The observation of superconductivity and systematic Tc changes with nanostructure make this synthesis approach of particular interest for realizing hybrid systems in the search of 2D superconductivity and the design of novel electronic heterostructures.
“…As the temperature decreases, S of 2H-NbSe 2 increases slowly and changes sign from negative to positive around 75 K followed by a perceptible decrease at the onset of CDW transition on cooling. We have reported this in terms of the increase of electron mean free path length l(ε) in two-band model [14]. But for 4H-NbSe 2 , S rapidly increases with decreasing temperature and changes sign from negative to positive around 60 K followed by an anomaly, where S starts decreasing on cooling, at 42 K. We suggest that, this is due to the competition between the two average carriers in the presence of imperfections as we observed that the drop in S at CDW is large for larger RRR values.…”
Good-quality hexagonal NbSe 2 single crystals were prepared. In 2H-NbSe 2 , superconducting and charge density wave (CDW) transitions were found at T s = 7.4 K and T c = 35 K respectively as reported previously. We have noticed that these two transitions are changed to T c = 42 K and T s = 6.5 K, in 4H-NbSe 2 . Thermopower has shown clear anomaly at CDW transitions. The anisotropic upper critical field was calculated as ∼3 and 6.3 for 2H-and 4H-single crystals around t = 0.81, where t = T /T s , from resistivity and explained in terms of coherence length. From the relation, H c2 (T ) = H c2 (0)[1 − t 2 ], H l c2 (0) was calculated as ∼8.15 T and 16.98 T at t = 0.84 in 2H-NbSe 2 and 4H-NbSe 2 respectively. However, H t c2 (0) = 2.68 T for both single crystals.
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