Publications
MW-level Pulses from an All-Fiber and Self-Starting Femtosecond Oscillator
We present an all-fiber Mamyshev oscillator that generates 40 fs and 80 nJ pulses. The resulting 1.5-MW peak power is 20 times higher than that of prior all-fiber and self-starting lasers. © Optica Publishing Group 2022, © 2022 The Author(s)
Centre of mass location, flight modes, stability and dynamic modelling of gliders
Falling paper flutters and tumbles through air, whereas a paper airplane glides smoothly if its leading edge is appropriately weighted. We investigate this transformation from ‘plain paper’ to ‘paper plane’ through experiments, aerodynamic modelling and free flight simulations of thin plates with differing centre of mass (CoM) locations. Periodic modes such as fluttering, tumbling and bounding give way to steady gliding and then downward diving as the CoM is increasingly displaced towards one edge.
Dissipation-enabled hydrodynamic conductivity in a tunable bandgap semiconductor
Electronic transport in the regime where carrier-carrier collisions are the dominant scattering mechanism has taken on new relevance with the advent of ultraclean two-dimensional materials. Here, we present a combined theoretical and experimental study of ambipolar hydrodynamic transport in bilayer graphene demonstrating that the conductivity is given by the sum of two Drude-like terms that describe relative motion between electrons and holes, and the collective motion of the electron-hole plasma.
Quantum Phases of Transition Metal Dichalcogenide Moiré Systems
Moiré systems provide a rich platform for studies of strong correlation physics. Recent experiments on heterobilayer transition metal dichalcogenide Moiré systems are exciting in that they manifest a relatively simple model system of an extended Hubbard model on a triangular lattice. Inspired by the prospect of the hetero-transition metal dichalcogenide Moiré system's potential as a solid-state-based quantum simulator, we explore the extended Hubbard model on the triangular lattice using the density matrix renormalization group.
Skills-focused lab instruction improves critical thinking skills and experimentation views for all students
Instructional labs are fundamental to an undergraduate physics curriculum, but their possible learning goals are vast with limited evidence to support any particular goal. In this study, we evaluate the efficacy of labs with different goals and structures on students' critical thinking skills and views about experimentation, using an extensive database of survey responses from over 20 000 students at over 100 institutions.
Superfluidity in the one-dimensional Bose-Hubbard model
We study superfluidity in the one-dimensional Bose-Hubbard model using a variational matrix product state technique. We determine the superfluid density as a function of the Hubbard parameters by calculating the energy cost of phase twists in the thermodynamic limit. As the system is critical, correlation functions decay as power laws and the entanglement entropy grows with the bond dimension of our variational state. We relate the resulting scaling laws to the superfluid density.
Dipolar excitonic insulator in a moiré lattice
Two-dimensional moiré materials provide a highly controllable solid-state platform for studies of quantum phenomena1–3. To date, experimental studies have focused on correlated electronic states, whereas correlated bosonic states in moiré materials have received less attention. Here we report the observation of a correlated dipolar excitonic insulator—a charge-insulating state driven by exciton formation4—in a device where a WSe2 monolayer and WSe2/WS2 moiré bilayer are coupled via Coulomb interactions. The system is a Mott insulator when all the holes reside in the moiré layer.
Disentangling types of lattice disorder impacting superconductivity in Sr2RuO4by quantitative local probes
The unconventional superconductivity in Sr2RuO4 is infamously susceptible to suppression by small levels of disorder such that it has been most commonly studied in extremely high-purity bulk crystals. Here, we harness local structural and spectroscopic scanning transmission electron microscopy measurements in epitaxial thin films of Sr2RuO4 to disentangle the impact of different types of crystalline disorder on superconductivity.
Very-High Dynamic Range, 10,000 Frames/Second Pixel Array Detector for Electron Microscopy
Precision and accuracy of quantitative scanning transmission electron microscopy (STEM) methods such as ptychography, and the mapping of electric, magnetic, and strain fields depend on the dose. Reasonable acquisition time requires high beam current and the ability to quantitatively detect both large and minute changes in signal. A new hybrid pixel array detector (PAD), the second-generation Electron Microscope Pixel Array Detector (EMPAD-G2), addresses this challenge by advancing the technology of a previous generation PAD, the EMPAD.
Canonical approach to cation flux calibration in oxide molecular-beam epitaxy
Molecular-beam epitaxy (MBE) is the gold standard for the epitaxial growth of complex oxides with the best material properties as determined by respective figures of merit. Unfortunately, once more than one cation is involved in the material desired, MBE growth often becomes plagued by difficulties in stoichiometry control.