| 摘要: | 研究期間：10208~10307;The discreteness of the electron charges results in time-dependent fluctuations of dc electrical currents, called shot noises, in conductors and solid state devices. That means in a given time period, the number of electrons flowing through a conductor N vary from time to time. We therefore can establish a distribution P(N), representing the probability of counting N electrons through a conductor in a given time period. P(N) in a conductor is influenced by the conduction mechanisms and the interactions the electrons have. Consequently, the physics behind P(N) in various kinds of conductors is very rich. In the proposed three-year project, we will setup an experimental routine to obtain the whole electron counting probability distribution P(N), also called full counting statistics of electrons. The obtained electron counting statistics will reveal microscopic information about electrons in conductors which can hardly be extracted by other experimental methods. The origin focus of the project is to develop electron counters based on a type of sensitive electrometers utilizing single-electron tunneling effects at ultra-low temperatures, called radio-frequency single-electron transistors (RF-SETs). A RF-SET device is a SET connected to a LC tank circuit resonating at radio frequency range. By utilizing reflectometry on RF-SETs, we expect to realize electron counters that are sensitive to single electrons, have MHz or higher counting speeds, and are easy to integrate to mesoscopic systems on chips. The next focus is using the developed electron counters to investigate the electron counting statistics in two types of mesoscopic conductors: NISIN hybrid SETs (N, I and S stand for normal metal contact, insulating tunnel barrier, and superconducting metal island, respectively) and voltage-biased tunnel junctions. Those two systems generate electrical currents with known electron counting statistics, which should be easy to be characterized by the electron counters. NISIN hybrid SETs can produce itinerant and regular single electron beams which bear no statistical moment beyond the first moment. Voltage-biased tunnel junctions carry currents with Poissonian statistics due to the stochastic nature of electron tunnel events. We plan to use a Hanbury-Brown Twiss (HBT) intensity inference setup to observe the second order quantum coherence function g(2), and therefore, the second moment of electron counting statistics. We expect to see g(2) = 0 for electron beams from NISIN hybrid SETs and g(2) = 1 for beams from voltage-biased tunnel junctions. Moreover, we will either investigate the methodology of accessing the third and higher moments of counting statistics, or study the electron counting statistics in interesting mesoscopic systems such as one-dimensional (1D) systems, or both. We anticipate the proposed study will give us a tool to spot electron conduction in various mesoscopic systems and provide better pictures for microscopic origins of various electronic phenomena in solids. |
