Publications
Absence of 3a 0 charge density wave order in the infinite-layer nickelate NdNiO2
A hallmark of many unconventional superconductors is the presence of many-body interactions that give rise to broken-symmetry states intertwined with superconductivity. Recent resonant soft X-ray scattering experiments report commensurate 3a 0 charge density wave order in infinite-layer nickelates, which has important implications regarding the universal interplay between charge order and superconductivity in both cuprates and nickelates.
Pulsing the Applied Potential in Electrochemical CO2 Reduction Enhances the C2 Activity by Modulating the Dynamic Competitive Binding of *CO and *H
We explore dynamic electrocatalysis by pulsing the applied potential to modulate the temporal microenvironment during the electrochemical reduction of CO2. We focus on copper electrodes by virtue of their unique ability to bind *CO intermediates and enable C-C coupling to form high-value C2 products, such as ethylene or ethanol. We examine the well-known competition between *CO and *H for active sites, as their relative coverage is crucial for enhancing the formation of C2 products.
Upper bounds on superconducting and excitonic phase stiffness for interacting isolated narrow bands
Inspired by the discovery of superconductivity in moiré materials with isolated narrow bandwidth electronic bands, here we analyze critically the question of what is the maximum attainable Tc in interacting flat-band systems. We focus specifically on the low-energy effective theory, where the density-density interactions are projected to the set of partially filled flat bands. The resulting problem is inherently nonperturbative, where the standard mean-field approximation is not applicable.
Valley-Coherent Quantum Anomalous Hall State in AB-Stacked MoTe2/ W S e2 Bilayers
Moiré materials provide fertile ground for the correlated and topological quantum phenomena. Among them, the quantum anomalous Hall (QAH) effect, in which the Hall resistance is quantized even under zero magnetic field, is a direct manifestation of the intrinsic topological properties of a material and an appealing attribute for low-power electronics applications. The QAH effect has been observed in both graphene and transition metal dichalcogenide (TMD) moiré materials. It is thought to arise from the interaction-driven valley polarization of the narrow moiré bands.
Realization of the Haldane Chern insulator in a moiré lattice
The Chern insulator displays a quantized Hall effect without Landau levels. Theoretically, this state can be realized by engineering complex next-nearest-neighbour hopping in a honeycomb lattice—the so-called Haldane model. Despite its profound effect on the field of topological physics and recent implementation in cold-atom experiments, the Haldane model has not yet been realized in solid-state materials.
Exchange Bias Between van der Waals Materials: Tilted Magnetic States and Field-Free Spin–Orbit-Torque Switching
Magnetic van der Waals heterostructures provide a unique platform to study magnetism and spintronics device concepts in the 2D limit. Here, studies of exchange bias from the van der Waals antiferromagnet CrSBr acting on the van der Waals ferromagnet Fe3GeTe2 (FGT) are reported. The orientation of the exchange bias is along the in-plane easy axis of CrSBr, perpendicular to the out-of-plane anisotropy of the FGT, inducing a strongly tilted magnetic configuration in the FGT.
Fully Ab Initio Approach to Inelastic Atom-Surface Scattering
We introduce a fully ab initio theory for inelastic scattering of any atom from any surface exciting single phonons, and apply the theory to helium scattering from Nb(100). The key aspect making our approach general is a direct first-principles evaluation of the scattering atom-electron vertex. By correcting misleading results from current state-of-the-art theories, this fully ab initio approach will be critical in guiding and interpreting experiments that adopt next-generation, nondestructive atomic beam scattering. © 2024 American Physical Society.
Dehydration drives damage in the freezing of brittle hydrogels
It is widely known that freezing breaks soft, wet materials. However, the mechanism underlying this damage is still not clear. To understand this process, we freeze model, brittle hydrogel samples, while observing the growth of ice-filled cracks that break these apart. We show that damage is not caused by the expansion of water upon freezing, or the growth of ice-filled cavities in the hydrogel. Instead, local ice growth dehydrates the surrounding hydrogel, leading to drying-induced fracture.
Tapestry of dualities in decohered quantum error correction codes
Quantum error correction (QEC) codes protect quantum information from errors due to decoherence. Many of them also serve as prototypical models for exotic topological quantum matters. Investigating the behavior of the QEC codes under decoherence sheds light on not only the codes' robustness against errors but also new out-of-equilibrium quantum phases driven by decoherence. The phase transitions, including the error threshold, of the decohered QEC codes can be probed by the systems' Rényi entropies SR with different Rényi indices R.
Thermally generated spin current in the topological insulator Bi2Se3
We present measurements of thermally generated transverse spin currents in the topological insulator Bi2Se3, thereby completing measurements of interconversions among the full triad of thermal gradients, charge currents, and spin currents. We accomplish this by comparing the spin Nernst magneto-thermopower to the spin Hall magnetoresistance for bilayers of Bi2Se3/CoFeB. We find that Bi2Se3 does generate substantial thermally driven spin currents.