Fig. 2: Force time evolution under oscillating strain.

Time-dependent force results for the N ≈ 9 nanojunction of Fig. 1b with equilibrated shape, initial h₀ ≈ 2.75 nm, relaxed neck length d₀ ≈ 1 nm, average neck cross section area A ≈ 0.6 nm², oscillation frequency 50 MHz, T = 300 K. Blue dashed-dotted line: imposed lead-lead oscillating amplitude a(t). Large gray dots: extracted instantaneous force between the leads. Black solid line: sinusoidal fit \(F(t)={F}_{0}+(A{\sigma }_{0})\exp (i\omega t+i\phi )\) of the force. The fit parameter Aσ₀ is the resulting force magnitude. Note the change of rheological response with drastic increase of non-sinusoidal noise at and above \({a}_{0}^{* }\approx 0.16\) nm. Note also the prevalence of tensile (positive) force for all strains (see text). The same plot for the largest size of N ≈ 26 is shown on Supplementary Fig. 1.