CAREER: Quantum Phase Transitions and Dissipation in Superconducting Nanowires

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Non-technical Abstract The goal of this Faculty Early Career Development project at Johns Hopkins University is to investigate the quantum phase transitions and dissipation in superconducting nanowires. A quantum phase transition can be observed close to absolute zero temperature when some critical parameter of the system is varied, such as the diameter of the wire or an applied magnetic field. The nature of the transition generally depends on the structure of the nanowire and the unwanted noise from the environment. A new fabrication technique will be developed in order to achieve precise control of the microstructure of the nanowires. The coupling with the environment will be purposely introduced in a controlled and tunable way in order to study its effect on the quantum properties of the nanowires. These nanowires will represent an experimental realization of a model system for investigating the general behavior of quantum systems interacting with the environment. Besides advancing our understanding of the fundamental physics of mesoscopic superconductors and quantum systems in general, this project will serve to prepare graduate and undergraduate students for scientific careers, develop new web-based teaching tools, provide research opportunities to high school students and teachers, and build a solid basis for future research. Technical Abstract The goal of this Faculty Early Career Development project at Johns Hopkins University is to investigate the quantum phase transitions and dissipation in superconducting nanowires. Quantum phase transitions occur at the absolute zero of temperature and are driven by quantum fluctuations of some parameter, such as the diameter of the wire or a magnetic field. A new fabrication technique will be developed in order to achieve a precise control of the physical properties of the nanowires and special attention will be paid to investigating the effects of an applied magnetic field, and the details of transport in the non-superconducting regime. A cryostat with a dilution refrigerator and the appropriate filtering arrangements will be used to minimize the unwanted noise from the environment. The coupling with the environment will then be introduced in a controlled and tunable way, in order to study its impact on the quantum effects in the nanowires. Realizing tunable dissipation and coupling it into a superconducting nanowire will provide an important model system for investigating the general behavior of quantum systems interacting with the environment. Besides advancing our understanding of the fundamental physics of mesoscopic superconductors and quantum systems in general, this project will serve to prepare graduate and undergraduate students for scientific careers, develop new web-based teaching tools, provide research opportunities to high school students and teachers, and build a solid basis for future research.