Publications
Restructuring physics labs to cultivate sense of student agency
Instructional physics labs offer students unique opportunities to develop an understanding of experimentation. By transforming labs to be more open ended and experimentation focused, instructors can better support student agency and choice. In this study, we examine students’ overall sense of and perceptions about agency in two experimentation-focused labs: one course primarily taken by physics majors and another course primarily taken by engineering majors. We compare the sense of and perceptions about agency between the different courses and between men and women in each course.
Does filling-dependent band renormalization aid pairing in twisted bilayer graphene?
Magic-angle twisted bilayer graphene (MATBG) exhibits a panoply of many-body phenomena that are intimately tied to the appearance of narrow and well-isolated electronic bands. The microscopic ingredients that are responsible for the complex experimental phenomenology include electron–electron (phonon) interactions and nontrivial Bloch wavefunctions associated with the narrow bands.
Geometry of gene regulatory dynamics
Embryonic development leads to the reproducible and ordered appearance of complexity from egg to adult. The successive differentiation of different cell types that elaborate this complexity results from the activity of gene networks and was likened by Waddington to a flow through a landscape in which valleys represent alternative fates. Geometric methods allow the formal representation of such landscapes and codify the types of behaviors that result from systems of differential equations.
Importance of bulk excitations and coherent electron-photon-phonon scattering in photoemission from PbTe(111): Ab initio theory with experimental comparisons
This paper presents a fully ab initio many-body photoemission framework that includes coherent three-body electron-photon-phonon scattering to predict the transverse momentum distributions and the mean transverse energies (MTEs) of bulk photoelectrons from single-crystal photocathodes. The need to develop such a theory stems from the lack of studies that provide complete understanding of the underlying fundamental processes governing the transverse momentum distribution of photoelectrons emitted from single crystals.
Continuous Mott transition in semiconductor moiré superlattices
The evolution of a Landau Fermi liquid into a non-magnetic Mott insulator with increasing electronic interactions is one of the most puzzling quantum phase transitions in physics1–6. The vicinity of the transition is believed to host exotic states of matter such as quantum spin liquids4–7, exciton condensates8 and unconventional superconductivity1. Semiconductor moiré materials realize a highly controllable Hubbard model simulator on a triangular lattice9–22, providing a unique opportunity to drive a metal–insulator transition (MIT) via continuous tuning of the electronic interactions.
Computational synthesis of substrates by crystal cleavage
The discovery of substrate materials has been dominated by trial and error, opening the opportunity for a systematic search. We generate bonding networks for materials from the Materials Project and systematically break up to three bonds in the networks for three-dimensional crystals. Successful cleavage reduces the bonding network to two periodic dimensions. We identify 4693 symmetrically unique cleavage surfaces across 2133 bulk crystals, 4626 of which have a maximum Miller index of one.
Multivalued Inverse Design: Multiple Surface Geometries from One Flat Sheet
Designing flat sheets that can be made to deform into three-dimensional shapes is an area of intense research with applications in micromachines, soft robotics, and medical implants. Thus far, such sheets were designed to adopt a single target shape. Here, we show that through anisotropic deformation applied inhomogeneously throughout a sheet, it is possible to design a single sheet that can deform into multiple surface geometries upon different actuations. The key to our approach is development of an analytical method for solving this multivalued inverse problem.
Emission of particles from a parametrically driven condensate in a one-dimensional lattice
Motivated by recent experiments, we calculate particle emission from a Bose-Einstein condensate trapped in a single deep well of a one-dimensional lattice when the interaction strength is modulated. In addition to pair emission, which has been widely studied, we observe single-particle emission. Within linear response, we are able to write closed-form expressions for the single-particle emission rates and reduce the pair emission rates to one-dimensional integrals.
Glass phenomenology in the hard matrix model
We introduce a new toy model for the study of glasses: the hard-matrix model. This may be viewed as a single particle moving on SO(N), where there is a potential proportional to the one-norm of the matrix. The ground states of the model are 'crystals' where all matrix elements have the same magnitude. These are the Hadamard matrices when N is divisible by four. Just as finding the latter has challenged mathematicians, our model fails to find them upon cooling and instead shows all the behaviors that characterize physical glasses.
Maximizing spin-orbit torque generated by the spin Hall effect of Pt
Efficient generation of spin-orbit torques is central for the exciting field of spin-orbitronics. Platinum, the archetypal spin Hall material, has the potential to be an outstanding provider for spin-orbit torques due to its giant spin Hall conductivity, low resistivity, high stabilities, and the ability to be compatible with CMOS circuits. However, pure clean-limit Pt with low resistivity still provides a low damping-like spin-orbit torque efficiency, which limits its practical applications.