Exploring Dynamic Spin Correlations In Nanoscale Structures Via Microwave Transport Spectroscopy

University Of Cincinnati Main Campus, Cincinnati OH

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** One of the modern challenges of science is to learn how to control and manipulate basic quantum systems in order to create electronic devices with expanded functionalities. Achieving this goal requires an improved understanding of how small systems, which are known to be strongly influenced by their environment, behave when their conditions change over time. This award supports a project to investigate time-dependent properties of an electron confined to a very small region of space and interacting with nearby macroscopic conductors. Such an arrangement possesses a striking array of highly universal static properties due to a coherent collective behavior of the confined and the delocalized electrons referred to as the Kondo effect. The project will capitalize on extensive existing knowledge of the static properties of Kondo-correlated electrons and answer fundamental questions concerning their interaction with electromagnetic fields. Such knowledge will aid further development of concepts in dynamics of simple quantum systems under practically relevant, non-equilibrium conditions. The research will benefit the community pursuing coherent control of elementary quantum states and complement recent studies of correlated dynamics in bulk materials. Students involved in the project will be trained in state-of-the-art technology, develop research and critical problem solving and decision making skills and become prepared for careers in academe, industry and government. The project will generate research opportunities for enthusiastic high-school students, which will stimulate their interest in research and invite them to pursue careers in science. ****TECHNICAL ABSTRACT**** Controllable quantum dots formed by a lateral confinement of a two-dimensional electron gas in a semiconductor heterostructure have been used in recent years by several groups to test universal scaling properties and investigate non-equilibrium aspects of Kondo-correlated electrons. The latter is possible in a quantum dot because a local electric field near the magnetic "impurity", represented by an unpaired electron spin in the dot, can be created by applying a small bias between the macroscopic source and drain "leads" connected to the dot via tunnel barriers. This individual investigator award will support a project to extend such studies to a time-dependent regime and investigate dynamic properties of the Kondo state by subjecting the quantum dot to an oscillatory bias and /or gate voltage. The objective of the project is to test the predicted universality of observable properties with respect to frequency and the Kondo temperature, with the emphasis on the interplay between photon-mediated correlations and dissipation. Experiments will be performed with quantum dots made on a GaAs/AlGaAs semiconductor heterostructure in a specially constructed apparatus which permits precision measurements of the device conductance in the presence of a microwave-frequency field of tunable orientation, magnitude and frequency. Students involved in the project will be trained in state-of-the-art technology, develop research and critical problem solving and decision making skills and become prepared for careers in academe, industry and government. The project will generate research opportunities for enthusiastic high-school students, which will stimulate their interest in research and invite them to pursue careers in science.