One group has theoretically solved how the communication between two quantum dots can be influenced by light. The team shows ways to control the transfer of information or energy from one quantum dot to another. To do this, the researchers calculated the electronic structure of two quantum dots or Nanocrystals that act like quantum dots. The results can be used to simulate the movement of electrons in quantum dots in real time. The so-called quantum dots are a new class of materials with many applications. They are obtained by tiny semiconductor crystals with dimensions in the nanometer range. The optical and electrical properties can be controlled by the size of these crystals in the latest generations of flat screen televisions on the market, where they ensure particularly bright and high-resolution color reproduction. However, quantum dots are not only used as dyes, but also in solar cells or as semiconductor components. Additionally, they are used right up to the computing components called the qubits of a quantum computer.
Now a team led by Dr. Annika Bande at the HZB expanded the understanding of the interaction between different quantum dots by an atomistic perspective in a theoretical publication. Annika Bande heads the group of theory of electronic dynamics and spectroscopy at the HZB and is interested in the origins of quantum physical phenomena. Although quantum dots are extremely small nanocrystals, they are made up of thousands of atoms and multiples of electrons. Theoretical chemistry, which recently completed her doctorate at Freie Universität, emphasizes that the electronic structure of such a semiconductor crystal can hardly be calculated with supercomputers. Though, the developed methods hardly describe the problem. In this case, we are working with reduced versions of quantum dots of only about a hundred atoms which have the characteristic properties of real nanocrystals.
With this approach, after a year and a half of development and in collaboration with Professor Jean Christophe Tremblay from the CNRS-Université de Lorraine in Metz, they were able to simulate the interaction of two quantum dots, each made up of hundreds of atoms. In concrete, we investigated how these two quantum dots can permanently absorb, exchange and store the energy controlled by light. A first light pulse is used for excitation, while the second light pulse induces storage. Researchers examined three different pairs of quantum dots to capture the influence of size and geometry. Further, they calculated the electronic structure with the highest precision and simulate the electronic movement in real time with a resolution of femtoseconds (10-15 s).
