Strong Correlation Between Superconductivity and Ferromagnetism in an Fe-Chalcogenide Superconductor

Abstract

The interplay among topology, superconductivity, and magnetism promises to bring a plethora of exotic and unintuitive behaviors in emergent quantum materials. The family of Fechalcogenide superconductors FeTexSe1-x are directly relevant in this context due to their intrinsic topological band structure, high-temperature superconductivity, and unconventional pairing symmetry. Despite enormous promise and expectation, the local magnetic properties of FeTexSe1x remain largely unexplored, which prevents a comprehensive understanding of their underlying material properties. Exploiting nitrogen vacancy (NV) centers in diamond, here we report nanoscale quantum sensing and imaging of magnetic flux generated by exfoliated FeTexSe1-x flakes, providing clear evidence of superconductivity-induced ferromagnetism in FeTexSe1-x. The coexistence of superconductivity and ferromagnetism in an established topological superconductor opens up new opportunities for exploring exotic spin and charge transport phenomena in quantum materials. The demonstrated coupling between NV centers and FeTexSe1-x may also find applications in developing hybrid architectures for next-generation, solid-state-based quantum information technologies.

Quantum Sensing and Imaging of Spin–Orbit‐Torque‐Driven Spin Dynamics in the Non‐Collinear Antiferromagnet Mn3Sn

“…The entire sequence is repeated ≈15 000 times during one camera exposure period and the frequency f of the microwave π pulses is swept for different camera exposure periods. [ 33 ] When f matches the NV electron spin resonance (ESR) conditions, NV spins are excited to the m s = ±1 states, emitting reduced red photoluminescence (PL), which can be optically addressed. By measuring the splitting of the NV ESR energies via optically detected magnetic resonance measurements, the magnitude of the local magnetic field experienced by individual NV spins B NV can be quantitatively measured as: B NV = π( f + − f − )/γ, [ 26 ] where γ is the gyromagnetic ratio and f ± correspond to the NV ESR frequencies of the m s = 0 ⟷ ± 1 transitions.…”

“…To address these challenges, we employ nitrogen-vacancy (NV) centers, optically active atomic defects in diamond that act as single-spin sensors, [26][27][28][29][30][31] to perform nanoscale quantum sensing and imaging of Mn 3 Sn films. Exploiting the NV widefield magnetometry technique, [32][33][34][35] we directly accessed the local magnetic textures of Mn 3 Sn films at a sub-micrometer length scale and imaged the spin-orbit-torque (SOT)-driven [36] deterministic magnetic switching [4] and chiral spin rotation. [5,19] Employing NV relaxometry, [37][38][39][40][41] we observed the dipole-dipole coupling between the spin dynamics of Mn 3 Sn and proximate NV centers, providing an attractive solid-state platform to develop NV-based hybrid architectures for quantum technological applications.…”

Pervasive beyond Room-Temperature Ferromagnetism in a Doped van der Waals Magnet

“…Given its ability to detect magnetic field with high-sensitivity and high spatial resolution, the NV center in diamond realizes a powerful quantum sensor of local magnetic field and hence provides an enabling tool for advancing condensed matter physics and materials science [32]. In particular, the implementation of NV sensing in the form of wide-field magnetic imaging has been applied to study novel electrical flow in graphene [33], vdW superconductors [34], as well as 2D magnets both at low-temperatures [35] as well as at room-temperature [27]. Hence, QMI provides a highly suitable tool for our investigation.…”

Dislocation Majorana Bound States in Iron-based Superconductors

“…Finally, following the experimental observations of FeTe 1−x Se x in Ref. [38] and [39], we introduce uniform surface ferromagnetism to both top and bottom (001) surfaces in a finite-size slab geometry, with N z layers stacked along ẑ direction.…”