Ultrafast Ti: Sapphire Amplifier for Studying Floquet-Bloch States in Novel Quantum
Abstract
This proposal requests funds for the acquisition of an ultrafast Ti:Sapphire amplifier laser and an optical parametric amplifier (OPA) to be used for time- and angle-resolved photoemission spectroscopy (tr-ARPES). This laser system will enable studying light dressed electronic states in a wide range of materials that are currently not possible. Recently, the PIÕs group used tr-ARPES to observe light dressed electronic states in solids for the first time. Briefly, periodic perturbation with low energy light below the absorption threshold leads to hybridization of Bloch electrons inside the solid with laser photons. In ARPES, these states are manifested as replica bands (Floquet-Bloch states), which behave as fully coherent real bands. Since then, there have been several proposals in different material systems based on using Floquet-Bloch states to engineer new hybrid band structures to realize new phases of materials. Experimentally, however, observation of Floquet-Bloch states has so far been limited to topological insulators (TIs). The reason is not related to their topological properties. It is rather mostly due to small Fermi wave-vector of these materials, which makes it possible to study them using low energy laser based ARPES at 6 eV. Generating Floquet-Bloch states requires intense low energy light since the intensity of the replica bands are proportional to light intensity and inversely proportional to laser frequency. With our existing laser, most of the laser pulse energy needs to be spent generating the required low frequency pump pulses using nonlinear optics with an OPA. The remaining small part of the laser pulse is used to generate harmonics of the laser for photoemission. Currently, the available laser pulse energy limits us to only 4th harmonic at 6 eV for performing tr-ARPES with OPA. This practically constrains these experiments to zone center, so only small Fermi wave vector materials such as TIs can be studied. In order to study Floquet-Bloch states in systems beyond TIs, it is crucially important to be able to simultaneously use an OPA and generate higher harmonics beyond 6 eV. We have already demonstrated HHG based ARPES in our lab with extreme ultraviolet (XUV) pulses (10-40 eV) with record energy resolution. With the acquisition of this laser system, it will be possible to combine this world class HHG setup and an OPA, which is crucially important for observing light dressed electronic states in a wide range of materials such as graphene, transition-metal dichalcogenides (TMDs) and Weyl semimetals.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 25, 2021
- Source ID
- W911NF2110174
Entities
People
- Nuh Gedik
Organizations
- Army Contracting Command
- Massachusetts Institute of Technology
- United States Army