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Prof. Barkai's Lab

Prof. Barkai's Lab


Tel: 972-3-531-7020


Photonics and Optics Research

Prof. Eli Barkai, of the Department of Physics, is a member of the Nano Materials Center at the Institute of Nanotechnology and Advanced Materials (BINA).  In Barkai's laboratory, the focus is primarily on theoretical issues in non-equilibrium statistical mechanics, and single molecule spectroscopy.

The group is particularly interested in the interface between quantum optics, statistical physics, and bio-physics.  They develop mathematical models to describe weak ergodicity breaking, and phenomenological models that describe dynamics of single molecules in live cells.

Nano-Science: Blinking Quantum Dots

Barkai's team is developing analytical theories about the light emitted from nano-crystals, specifically the non-ergodic features of these single emitters. Fluorescence intermittency, or blinking, is the phenomenon of random switching between ON (bright) and OFF (dark) states of the emitter under continuous excitation. Frequently seen in nanoscale emitters such as molecular fluorophores and colloidal quantum dots, blinking is related to the competition between the radiative and non-radiative relaxation pathways. In most cases, the peculiar feature of such blinking is power-law, rather than exponential, statistics of the ON and OFF time distributions.  As a result, the measurements of the time-averaged intensity of a single emitter are not reproducible in different experiments, implying complex dynamics of the involved process. In other words, in one experiment the emitter can blink frequently, while in another it may stay ON or OFF for almost the entire length of the experiment (even for extremely long measurement times).

Nano-Biology: Dynamics of Single Molecules in the Cell

Individual molecules in living cells exhibit unusual, non-ergodic behavior. For example, the time averaged mean square displacement of mRNA in an e-coli cell does not follow normal diffusion, and is non-reproducible, varying from one measurement to another. This phenomenon, which is completely inconsistent with ordinary Brownian motion, inspired our team to explore the fundamental difference between averages over single long trajectories of individual particles and the corresponding ensemble averages.

Rapid Dynamics of Single Molecules

Dynamics of single molecules are typically investigated with continuous wave laser fields, a useful method for slow dynamics - beyond nano seconds. However, Barkai's team has developed theoretical tools based on non-linear, single molecule techniques, to investigate rapid dynamics of single molecules, and generation of single photons from single molecule sources.  

Fractional Kinetic Equations

They are also developing a theory for fractional kinetic equations, which describes slow relaxation and diffusion in a wide variety of disordered systems. Usually, physical modeling is based on ordinary differential equations, with integer order derivatives such as d^n / dt ^n and n=1,2,3. However, Barkai's group is using fractional calculus with non-integer derivatives such as d^{1/2} d t^{1/2} to model anomalous diffusion and weak ergodicity breaking of molecules in the cell.

Barkai was awarded the 2006 Krill Prize for Excellence in Scientific Research, the 2010 Michael Bruno Award, and the 2011 Bessel Award by the Alexander von Humboldt Foundation.

Last updated on 21/5/14