Unconventional Meissner screening induced by chiral molecules in a conventional superconductor

TL;DR

This study demonstrates that adsorbing chiral molecules on a conventional superconductor alters its Meissner effect by inducing odd-frequency spin-triplet states, suggesting a new way to generate unconventional superconducting states.

Contribution

It reveals that chiral molecules can induce long-range odd-frequency spin-triplet pairing in conventional superconductors, providing a simpler alternative to complex hybrid systems.

Findings

Chiral molecules modify the magnetic field profile inside Nb superconductors.

Induction of odd-frequency spin-triplet states by chiral molecules.

Modification of the Meissner response depends on the applied magnetic field direction.

Abstract

The coupling of a superconductor to a different material often results in a system with unconventional superconducting properties. A conventional superconductor is a perfect diamagnet expelling magnetic fields out of its volume, a phenomenon known as Meissner effect. Here, we show that the simple adsorption of a monolayer of chiral molecules, which are non-magnetic in solution, onto the surface of a conventional superconductor can markedly change its diamagnetic Meissner response. By measuring the internal magnetic field profile in superconducting Nb thin films under an applied transverse field by low-energy muon spin rotation spectroscopy, we demonstrate that the local field profile inside Nb is considerably modified upon molecular adsorption in a way that also depends on the applied field direction. The modification is not limited to the chiral molecules/Nb interface, but it is long ranged and occurs over a length scale comparable to the superconducting coherence length. Zero-field muon spin spectroscopy measurements in combination with our theoretical analysis show that odd-frequency spin-triplet states induced by the chiral molecules are responsible for the modification of the Meissner response observed inside Nb. These results indicate that a chiral molecules/superconductor system supports odd-frequency spin-triplet pairs due to the molecules acting as a spin active layer and therefore they imply that such system can be used as a simpler alternative to superconductor/ferromagnet or superconductor/topological insulator hybrids for the generation and manipulation of unconventional spin-triplet superconducting states.