Studies of Spin-Currents, Anomalous Hall Effect and Ballistic Electron Propagation in Quench Condensed Alkali Films

University Of Southern California, Los Angeles CA

Investigators

Abstract

This individual investigator award is to study the properties of alkali metal films that get modified when they are in contact with other materials. Alkali metals have the unique property that even in quench-condensed films the conduction electrons have long mean free paths. With quenched condensation, complex sandwiches can be prepared and the ballistic propagation of conduction electrons can be investigated in situ. Alkali films in weak contact with Fe films show strong spin currents. One focus of the proposed research is the study of spin currents and the anomalous Hall effect. Both phenomena have attracted strong interest in recent years because of their importance in the field of spintronics. Furthermore, alkali metal films have found important applications in the storage of hyperpolarized noble gases (which are used in MRI of the lungs). Only containers covered with alkali films can store the hyperpolarized noble gases over a sufficiently long time and the cause of it is not understood at present. The project introduces graduate and undergraduate students to the techniques of high vacuum, low temperature, and thin film physics. Undergraduate students who participated in previous research projects in the principal investigator's group have won first and second prizes in university-wide undergraduate research competition. Films of alkali metals became recently important in the medical application of MRI to the lungs and other air filled organs. For the MRI of the lungs, one needs hyperpolarized noble gases (for example He3). Only containers covered with alkali films can store these gases for sufficiently long times. The property of alkali metals that makes this possible is not clear at present. Within the proposed project, the modified properties of alkali films when in contact with other material will be investigated. Alkali films have the unique property that they form a rather perfect lattice even when they are condensed onto a liquid-helium-cooled substrate. Therefore, the ballistic propagation of conduction electrons can be investigated in complex multi-films of alkali and other metals. The project focuses on the investigation of spin currents in iron-alkali multi-films and the properties of thin alkali films in contact with other materials. The project introduces graduate and undergraduate students to the techniques of high vacuum, low temperature, and thin film physics and trains them as competent workers for frontier scientific research. Undergraduate students who participated in previous research projects in the principal investigator's group have won first and second prizes in university-wide undergraduate research competition.