Publications
Nonequilibrium fractional Hall response after a topological quench
We theoretically study the Hall response of a lattice system following a quench where the topology of a filled band is suddenly changed. In the limit where the physics is dominated by a single Dirac cone, we find that the change in the Hall conductivity is two-thirds of the quantum of conductivity. We explore this universal behavior in the Haldane model and discuss cold-atom experiments for its observation. Beyond the linear response, the Hall effect crosses over from fractional to integer values. We investigate finite-size effects and the role of harmonic confinement.
DNA looping mediates nucleosome transfer
Proper cell function requires preservation of the spatial organization of chromatin modifications. Maintenance of this epigenetic landscape necessitates the transfer of parental nucleosomes to newly replicated DNA, a process that is stringently regulated and intrinsically linked to replication fork dynamics. This creates a formidable setting from which to isolate the central mechanism of transfer.
A Balance between Secreted Inhibitors and Edge Sensing Controls Gastruloid Self-Organization
The earliest aspects of human embryogenesis remain mysterious. To model patterning events in the human embryo, we used colonies of human embryonic stem cells (hESCs) grown on micropatterned substrate and differentiated with BMP4. These gastruloids recapitulate the embryonic arrangement of the mammalian germ layers and provide an assay to assess the structural and signaling mechanisms patterning the human gastrula.
Airborne Acoustic Perception by a Jumping Spider
Jumping spiders (Salticidae) are famous for their visually driven behaviors [1]. Here, however, we present behavioral and neurophysiological evidence that these animals also perceive and respond to airborne acoustic stimuli, even when the distance between the animal and the sound source is relatively large (∼3 m) and with stimulus amplitudes at the position of the spider of ∼65 dB sound pressure level (SPL).
DNA supercoiling during transcription
The twin-supercoiled-domain model describes how transcription can drive DNA supercoiling, and how DNA supercoiling, in turn, plays an important role in regulating gene transcription. In vivo and in vitro experiments have disclosed many details of the complex interactions in this relationship, and, recently, new insights have been gained with the help of genome-wide DNA supercoiling mapping techniques and single-molecule methods.
Measuring nonlinear stresses generated by defects in 3D colloidal crystals
The mechanical, structural and functional properties of crystals are determined by their defects, and the distribution of stresses surrounding these defects has broad implications for the understanding of transport phenomena. When the defect density rises to levels routinely found in real-world materials, transport is governed by local stresses that are predominantly nonlinear. Such stress fields however, cannot be measured using conventional bulk and local measurement techniques.
Observation of semilocalized dispersive states in the strongly correlated electron-doped ferromagnet Eu1-xGdx O
Chemical substitution plays a key role in controlling the electronic and magnetic properties of complex materials. For instance, in EuO, carrier doping can induce a spin-polarized metallic state and colossal magnetoresistance, and significantly enhance the Curie temperature. Here, we employ a combination of molecular-beam epitaxy, angle-resolved photoemission spectroscopy, and an effective model calculation to investigate and understand how semilocalized states evolve in lightly electron-doped Eu1-xGdxO above the ferromagnetic Curie temperature.
Self-organization of human embryonic stem cells on micropatterns
Fate allocation in the gastrulating embryo is spatially organized as cells differentiate into specialized cell types depending on their positions with respect to the body axes. There is a need for in vitro protocols that allow the study of spatial organization associated with this developmental transition. Although embryoid bodies and organoids can exhibit some spatial organization of differentiated cells, methods that generate embryoid bodies or organoids do not yield consistent and fully reproducible results.
NaSn2As2: An Exfoliatable Layered van der Waals Zintl Phase
The discovery of new families of exfoliatable 2D crystals that have diverse sets of electronic, optical, and spin-orbit coupling properties enables the realization of unique physical phenomena in these few-atom-thick building blocks and in proximity to other materials.
Origin of fieldlike spin-orbit torques in heavy metal/ferromagnet/oxide thin film heterostructures
We report measurements of the thickness and temperature (T) dependencies of current-induced spin-orbit torques, especially the fieldlike (FL) component, in various heavy metal (HM)/normal metal (NM) spacer/ferromagnet (FM)/oxide (MgO and HfOx/MgO) heterostructures. The FL torque in these samples originates from spin current generated by the spin Hall effect in the HM.