CAREER: Mesoscopic Quantum Opto-Electronics in Gate-Defined Transition Metal Dichacogenide Nanostructures

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

The electronic properties of a solid can undergo dramatic change when its thickness is reduced to the atomic limit. A family of semiconductors with single-atom thickness, transition metal dichalcogenides (TMD), host unique electronic and optical properties that can potentially provide solutions to many remaining challenges in future electronics and computing platforms. This CAREER project investigates these novel material properties with versatile experimental control, towards understanding and harnessing them in realizing novel device concepts with improved performance and operation schemes. The research underpins electronic device applications that can be particularly relevant in low energy electronics and sensing. If successful, the project also lays a foundation towards future semiconductor-based computing platforms that promises (1) smaller device dimensions and higher-level integration, (2) new computation paradigms with higher computational power and efficiency, and (3) new communication protocols with enhanced information security. Multiple graduate students, and undergraduates are being educated through this project in an interdisciplinary research environment. A series of educational and outreach efforts are being implemented, aimed towards enhanced training of the next generation scientific and engineering work-force, including (1) development of a new course on device physics directed towards an interdisciplinary student audience, (2) enhancing the well-established "Method for Experimental Physics" course by providing a new module of low-temperature physics experiments for physics undergraduate students, (3) and recruitment of underrepresented groups into interdisciplinary research and partnership with the Science Museum of Minnesota on K-12 education and outreach, promoting public awareness toward the advanced nanotechnologies and solid-state physics. Electron spins – a form of quantized angular momentum, are widely used to define the 0 and 1 states of a single quantum bit. In transition metal dichalcogenides (TMDs), the electron spin is effectively locked to another quantum degree of freedom, valley. This provides new ways of defining and manipulating a spin-valley quantum bit with potentially enhanced life time and robustness, as it is much more difficult to accidentally flip the valley quantum degree of freedom with electrical and magnetic fluctuations. In addition, the in-plane electrostatic interactions in TMDs are much stronger compared to conventional semiconductors, allowing controllable light-matter interaction. This can be utilized to convert the electronic quantum information to photonic states, a process essential for long distance quantum communication between future electronic quantum computers. This CAREER research focuses on studying exotic quantum phenomena in gate-defined TMD nanostructures via electrical and optical quantum measurements and providing proof-of-principle demonstration of new quantum device functionalities, such as manipulation of the combined spin-valley quantum degree of freedom, tunable strong in-plane and vertical electron coupling, and coherence transduction of quantum information between electronic and optical states. By studying electrostatically-controlled quantum tunneling processes, this CAREER project also provides sensitive characterization of material metrics associated with small energy scales that are difficult to access with conventional transport and optical studies. The more complicated gate-defined nanostructures provide platforms to study novel spin-valley-locked Coulomb drag and spin-valley polarized mesoscopic quantum physics, which provides a basis for novel quantum device concepts such as valleytronics and spin-valley qubits. Gate-defined quantum confinement and manipulation of optical excitations allow the study of novel exciton and condensate physics with tunable confinement-enhanced large exciton binding energy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.