  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.
