Competition between orbital effects, Pauli limiting, and Fulde-Ferrell-Larkin-Ovchinnikov states in 2D transition metal dichalcogenide superconductors

Abstract

We compare the upper critical field of bulk single-crystalline samples of the two intrinsic transition metal dichalcogenide (TMD) superconductors, 2H-NbSe2 and 2H-NbS2, in high magnetic fields where their layer structure is aligned strictly parallel and perpendicular to the field, using magnetic torque experiments and a high-precision piezo-rotary positioner. While both superconductors show that orbital effects still have a significant impact when the layer structure is aligned parallel to the field, the upper critical field of NbS2 rises above the Pauli limiting field and forms a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, while orbital effects suppress superconductivity in NbSe2 just below the Pauli limit. From the out-of-plane anisotropies, the coherence length perpendicular to the layers of 31 Å in NbSe2 is much larger than the interlayer distance, leading to a significant orbital effect suppressing superconductivity before the Pauli limit is reached, in contrast to the more 2D NbS2.

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Cited by in corpus (5)

• Ising superconductivity in noncentrosymmetric bulk NbSe2
• Investigating the superconducting state of 2$H$-NbS${}_2$ as seen by the vortex lattice
• Two characteristic contributions to the superconducting state of 2$H$-NbSe${}_2$
• Orbital Fulde-Ferrell-Larkin-Ovchinnikov state in 2H-NbS2 flakes
• The Anisotropy of Thermal Activation Energy of 2H-NbS${}_2$