Publications
Vector-resolved magnetooptic kerr effect measurements of spin-orbit torque
We demonstrate simultaneous detection of current-driven dampinglike and fieldlike spin-orbit torques in heavy metal/ferromagnetic metal bilayers by measuring all three magnetization components mx,my, and mz using a vector-resolved magnetooptic Kerr effect (MOKE) technique based on quadrant detection. We investigate the magnitude and direction of spin-orbit torques in a series of platinum/permalloy samples, finding good agreement with results obtained via polar and quadratic MOKE measurements without quadrant detection. © 1965-2012 IEEE.
Visualizing electronic quantum matter
Modern quantum materials support a wide variety of exotic and unanticipated states of quantum matter and differ radically in phenomenology from conventional systems such as metals, semiconductors, band insulators, and ferromagnets. For example, quantum materials exhibit states such as electron liquid crystals, fluids of fractionalized quantum particles, quantum-entangled spin liquids, and topologically protected composite quantum particles.
High-Performance Image-Based Measurements of Biological Forces and Interactions in a Dual Optical Trap
Optical traps enable the nanoscale manipulation of individual biomolecules while measuring molecular forces and lengths. This ability relies on the sensitive detection of optically trapped particles, typically accomplished using laser-based interferometric methods. Recently, image-based particle tracking techniques have garnered increased interest as a potential alternative to laser-based detection; however, successful integration of image-based methods into optical trapping instruments for biophysical applications and force measurements has remained elusive.
Measurements of Oxygen Electroadsorption Energies and Oxygen Evolution Reaction on RuO 2 (110): A Discussion of the Sabatier Principle and Its Role in Electrocatalysis
We report the hydroxide (OH ad ) and oxide (O ad ) experimental electroadsorption free energies, their dependences on pH, and their correlations to the oxygen evolution reaction (OER) electrocatalysis on RuO 2 (110) surface. The Sabatier principle predicts that catalyst is most active when the intermediate stabilization is moderate, not too strong such that the bound intermediate disrupts the subsequent catalytic cycle, nor too weak such that the surface is ineffective.
Common glass-forming spin-liquid state in the pyrochlore magnets Dy2Ti2 O7 and Ho2Ti2 O7
Despite a well-ordered pyrochlore crystal structure and strong magnetic interactions between the Dy3+ or Ho3+ ions, no long-range magnetic order has been detected in the pyrochlore titanates Ho2Ti2O7 and Dy2Ti2O7. To explore the actual magnetic phase formed by cooling these materials, we measure their magnetization dynamics using toroidal, boundary-free magnetization transport techniques.
Cluster representations and the Wolff algorithm in arbitrary external fields
We introduce a natural way to extend celebrated spin-cluster Monte Carlo algorithms for fast thermal lattice simulations at criticality, such as the Wolff algorithm, to systems in arbitrary fields, be they linear magnetic vector fields or nonlinear anisotropic ones. By generalizing the "ghost spin" representation to one with a "ghost transformation," global invariance to spin symmetry transformations is restored at the cost of an extra degree of freedom which lives in the space of symmetry transformations. The ordinary cluster-building process can then be run on the representation.
Fast semistochastic heat-bath configuration interaction
This paper presents in detail our fast semistochastic heat-bath configuration interaction (SHCI) method for solving the many-body Schrödinger equation. We identify and eliminate computational bottlenecks in both the variational and perturbative steps of the SHCI algorithm. We also describe the parallelization and the key data structures in our implementation, such as the distributed hash table.
Quantum Spin Liquid Intertwining Nematic and Superconducting Order in Fese
Despite its seemingly simple composition and structure, the pairing mechanism of FeSe remains an open problem due to several striking phenomena. Among them are nematic order without magnetic order, nodeless gap and unusual inelastic neutron spectra with a broad continuum, and gap anisotropy consistent with orbital selection of unknown origin. Here we propose a microscopic description of a nematic quantum spin liquid that reproduces key features of neutron spectra. We then study how the spin fluctuations of the local moments lead to pairing within a spin-fermion model.
Phase diagram of Bi2Sr2CaCu2O8+δ revisited
In cuprate superconductors, the doping of carriers into the parent Mott insulator induces superconductivity and various other phases whose characteristic temperatures are typically plotted versus the doping level p. In most materials, p cannot be determined from the chemical composition, but it is derived from the superconducting transition temperature, Tc, using the assumption that the Tc dependence on doping is universal.
A 250 μm × 57 μm Microscale Opto-electronically Transduced Electrodes (MOTEs) for Neural Recording
Recording neural activity in live animals in vivo with minimal tissue damage is one of the major barriers to understanding the nervous system. This paper presents the technology for a tetherless opto-electronic neural interface based on 180 nm CMOS circuits, heterogeneously integrated with an AlGaAs diode that functions as both a photovoltaic and light emitting diode.