Fig. 2
From: Discovery of a strain-stabilised smectic electronic order in LiFeAs
Modulated phase of LiFeAs strained along [110]. a, b Topographic images taken from the same position on the modulated phase at a Vs = +17 mV and b Vs = −18 mV (both Is = 50 pA). A red arrow indicates the direction of the strain. Crosses mark the position of the same point defect. Dashed lines highlight the phase shift of the modulation between the two images. c Topographic image (Vs = +15 mV, Is = 0.25 nA) and (inset, Vs = −50 mV, Is = 0.3 nA) an atomically resolved image of unstrained LiFeAs. Scale bars in a–c 5 nm, in inset of c 1 nm. d Topography of the modulated phase (12.4 × 3.1 nm2, Vs = 25 mV, Is = 0.1 nA). e Differential conductance g(x, V) as a function of position and bias voltage across the stripes, along the solid line in d (Vs = 25 mV, Is = 0.3 nA). f dI/dV spectra recorded from the central positions on and off the stripes (areas indicated by solid and dashed rectangle in d, respectively; Vs = 30 mV, Is = 0.5 nA). Arrows mark the bias voltages where the contrast of the charge modulation in e is strongest. A spectrum obtained on unstrained LiFeAs (dashed grey line, T = 1.5 K, Vs = −50 mV, Is = 0.3 nA) is included for comparison. The spectra were normalised at V = 30 mV. Unless stated otherwise, all data in a,b, d–f have been recorded at T = 4K. g (Top panel) Spatial variance \(\sigma ^2\left( V \right) = \left\langle {l\left( {{\mathbf{x}},V} \right)^2} \right\rangle _{\mathbf{x}} - \left\langle {l\left( {{\mathbf{x}},V} \right)} \right\rangle _{\mathbf{x}}^2\) of the calculated normalised conductance l(x, V) = g(x, V)/(I(x, V)/V) as a function of bias voltage, extracted from e. Dashed vertical lines mark the positions of the charge modulation peaks. (Bottom panel) Wave-vector of the spatial modulation of l(x, V) as a function of bias voltage. Error bars are obtained from the non-linear least squares fit to the experimental data in e and represent the 1σ confidence interval. A red line shows the average wave vector of 0.139q0. Inside the superconducting gap (shaded grey), l(x, V) becomes unreliable because the current becomes very small
