Fig. 4: Characterization of coupled quantum resonance states in COS-OQCs.

a STM image of a symmetric COS-OQC (V = −0.32 V, I = 1.5 nA). b Point dI/dV spectra acquired over different sites inside a symmetric COS-OQC and Au(111) substrate. dI/dV curves taken at the neck (blue curve) and 1.23 nm away from the neck of symmetric COS-OQC (red curve). c STM image of an asymmetric COS-OQC (V = −0.3 V, I = 1.5 nA). d Point dI/dV spectra acquired over different sites inside an asymmetric COS-OQC and Au(111) substrate. dI/dV curves taken at the neck (blue curve) and 1.4 nm away from the neck of an asymmetric COS-OQC (red curve). e, f Constant-current dI/dV maps recorded at different energy positions over a symmetric COS-OQC (I = 1 nA for e, f). Panels e, f refer to the bonding (−0.32 V) and antibonding (−0.18 V) states, respectively. g, h Constant-current dI/dV maps recorded at different energy positions over an asymmentric COS-OQC (I = 1 nA for g, h). Panels g, h refer to the bonding (−0.3 V) and antibonding (−0.15 V) states, respectively. i, j Simulated spectral function maps of a symmetric COS-OQC acquired at different energy positions corresponding to bonding (−0.36 eV) and antibonding states (−0.25 eV), respectively. k, l Simulated spectral function maps of an asymmetric COS-OQC acquired at different energy positions corresponding to bonding (−0.34 eV) and antibonding states (−0.24 eV), respectively. Scale bar: 5 Å.