Ultrafast spectroscopy of quantum materials

点击翻译按钮获取中文摘要

Your toaster gives your morning bread its crunch by passing electrical current through a coil of wire, causing the wire to become red hot and your bread a golden brown. The wire heats up because the electrons flowing through it flow imperfectly, bumping into microscopic imperfections in the metal as they move, transforming the electrical energy supplied by your outlet into heat energy. The same process is responsible for the much less desirable electrical losses found in power lines and computer chips. In typical metals, the average time that an electron travels freely before bumping into something is a few millionths of a billionth of one second, or a few femtoseconds. For a sense of the brevity of this unit of time, it takes about one hundred femtoseconds for a beam of light to travel the width of a human hair. The experiments funded by this research grant will help us to understand the processes that inhibit the flow of electrons in materials, by employing new technology to generate laser pulses with femtosecond duration. Since these pulses are comparable in length to the average time between electron collisions, they can be used to observe the motion of electrons in real time as they respond to an electrical impulse. Much in the way a movie camera reproduces motion with a series of still photographs separated by a thirtieth of a second, we can make a series of electrical measurements, using the laser pulses to limit the time of observation to a few femtoseconds. Armed with these ultrafast movies of electronic motion in solids, we will be able to improve our understanding of how different materials conduct electricity, and what factors limit that conduction. These studies are of considerable basic scientific interest, and Canadian researchers are known internationally for our contributions to knowledge in this area. Furthermore, the understanding provided by these studies may help us to engineer electronic materials for use in power lines, consumer electronics and electronic communications.