Fig. 4: Long-range coupling between YSR impurities on La(0001).
From: Long-range focusing of magnetic bound states in superconducting lanthanum
a Differential tunneling conductance map showing spatial modulations of the magnetic bound states around four YSR1 impurities. Two impurities (A and B) are separated by a distance of 3.6 nm, comparable to 10 atomic lattice constants on the La(0001) surface, while the other two (I1 and I2) are spatially isolated. IT = 1.0 nA, VS = 1.2 mV, T = 1.67 K. Scale bar: 5.0 nm. b Tunneling spectra obtained at the centers of the four magnetic impurities. Black dotted lines denote the energies of ±|ΔT + EYSR | for the isolated YSR1 impurities (I1 and I2) with EYSR = 0.56 meV. The edge of the superconducting gap (ΔT = 0.93 meV) of the La-coated tip is depicted by green dotted lines. Red and blue arrows indicate the peak positions at ±|ΔT + EYSR | for the interacting impurities A and B with EYSR = 0.47 ± 0.01 meV.
