A Rice team discovered those electrons can
Results from the Rice lab of condensed matter physicist Douglas Natelson appear in the American Chemical Society's Journal of Physical Chemistry Letters.
Natelson's lab studies the electronic, magnetic and optical properties of nanoscale structures, often by testing the properties of systems that can only be viewed under a microscope.
Some studies involve whole gold nanowires, and sometimes the lab breaks the wire to form a gap of just a few nanometers (billionths of a meter). One goal is to understand whether and how electrons leap the nanogap under various conditions, like ultracold temperatures.
While looking at such structures, the researchers found themselves studying the nanoscale characteristics of what's known as the Seebeck (thermoelectric) effect, discovered in 1821, in which heat is converted to electricity at the junction of two wires of different metals. Seebeck discovered that a voltage would form across a single conductor when one part is hotter than the other.
"If you want to make thermostats for your house or your car climate control, this is how you do it," Natelson said. "You join together two dissimilar metals to make a thermocouple, and stick that junction where you want to measure the temperature. Knowing the difference between the Seebeck coefficients of the metals and measuring the voltage across the thermocouple, you can work backward from that to get the temperature."
To see how it works in a single metal on the nanoscale, Natelson, lead author and former postdoctoral researcher Pavlo Zolotavin and graduate student Charlotte Evans used a laser to induce a temperature gradient across a bowtie-shaped gold nanowire. That created a small voltage, consistent with the Seebeck effect. But with a nanogap splitting the wire, "the data made clear that a different physical mechanism is at work," they wrote.
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