# Technical Data Extraction: Current Density Streamline Plots
This image contains two side-by-side scientific plots (labeled 'a' and 'c') representing current density streamlines in a nanostructure. The plots visualize the flow of current through a channel of varying width or potential.
## 1. Global Metadata
* **Language:** English
* **X-Axis Label (both plots):** `length (nm)`
* **X-Axis Scale:** -40 to 40 (with ticks at -40, -20, 0, 20, 40)
* **Y-Axis Label (both plots):** `width (nm)`
* **Y-Axis Scale:** -10 to 10 (with ticks at -10, 0, 10)
* **Color Scale:** Sequential heatmap (White $\rightarrow$ Light Orange $\rightarrow$ Dark Red).
* **Visual Elements:** Red streamlines with directional arrows pointing generally from left to right. A black horizontal arrow at the bottom of each plot indicates the primary direction of flow.
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## 2. Component Analysis
### Plot (a): $K_1: E_F = +0.035t$
* **Header Text:** `(a) K₁: E_F=+0.035t`
* **Color Bar Range:** 0.0 to ~0.35 (Ticks at 0.0, 0.1, 0.2, 0.3)
* **Spatial Grounding [x, y]:** The color bar is located to the right of the plot.
* **Trend Description:** The current density is high (dark red) and widely distributed across the width of the channel. The streamlines show a "pinched" behavior at regular intervals along the length (approximately at $x = -35, -5, 25$ nm).
* **Key Observations:**
* The flow is robust across the entire width (-10 to 10 nm).
* There are distinct "bubbles" or regions of lower density (white/light orange) centered at $y=0$ between the pinch points.
* The streamlines are densest (darkest red) near the edges of these central bubbles.
### Plot (c): $K_1: E_F = -0.035t$
* **Header Text:** `(c) K₁: E_F=-0.035t`
* **Color Bar Range:** 0.0 to ~0.45 (Ticks at 0.0, 0.2, 0.4)
* **Spatial Grounding [x, y]:** The color bar is located to the right of the plot.
* **Trend Description:** Compared to plot (a), the current density is significantly more concentrated along the horizontal center line ($y=0$). The intensity (darkness of red) is higher in the central core but drops off much faster toward the edges ($y = \pm 10$).
* **Key Observations:**
* The flow is "collimated" or focused toward the center.
* The pinch points are still visible but appear more as nodes in a narrow beam rather than the wide-channel oscillations seen in plot (a).
* The regions near the top and bottom boundaries ($y > 5$ and $y < -5$) show very low current density (white).
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## 3. Comparative Summary
| Feature | Plot (a) | Plot (c) |
| :--- | :--- | :--- |
| **Fermi Energy ($E_F$)** | $+0.035t$ (Positive) | $-0.035t$ (Negative) |
| **Max Intensity** | ~0.35 | ~0.45 |
| **Flow Distribution** | Wide; fills the 20nm width. | Narrow; concentrated at the center. |
| **Pattern** | Oscillatory wide-channel flow. | Focused beam-like flow with nodes. |
**Technical Conclusion:** The sign of the Fermi energy ($E_F$) dictates the spatial distribution of the current. A positive $E_F$ results in a more spread-out current density across the nanostructure's width, while a negative $E_F$ of the same magnitude causes the current to focus into a narrow central beam.
