Publications
Tunable shear thickening in suspensions
Shear thickening, an increase of viscosity with shear rate, is a ubiquitous phenomenon in suspended materials that has implications for broad technological applications. Controlling this thickening behavior remains a major challenge and has led to empirical strategies ranging from altering the particle surfaces and shape to modifying the solvent properties. However, none of these methods allows for tuning of flow properties during shear itself.
All-optical vector measurement of spin-orbit-induced torques using both polar and quadratic magneto-optic Kerr effects
We demonstrate that the magneto-optic-Kerr effect with normal light incidence can be used to obtain quantitative optical measurements of both components of spin-orbit-induced torque (both the antidamping and effective-field components) in heavy-metal/ferromagnet bilayers. This is achieved by analyzing the quadratic Kerr effect as well as the polar Kerr effect. The two effects can be distinguished by properly selecting the polarization of the incident light.
The Chd1 chromatin remodeler can sense both entry and exit sides of the nucleosome
Chromatin remodelers are essential for establishing and maintaining the placement of nucleosomes along genomic DNA. Yet how chromatin remodelers recognize and respond to distinct chromatin environments surrounding nucleosomes is poorly understood. Here, we use Lac repressor as a tool to probe how a DNA-bound factor influences action of the Chd1 remodeler. We show that Chd1 preferentially shifts nucleosomes away from Lac repressor, demonstrating that a DNA-bound factor defines a barrier for nucleosome positioning.
Shubnikov-de Haas quantum oscillations reveal a reconstructed Fermi surface near optimal doping in a thin film of the cuprate superconductor Pr1.86Ce0.14CuO4±δ
We study magnetotransport properties of the electron-doped superconductor Pr2-xCexCuO4±δ with x=0.14 in magnetic fields up to 92 T, and observe Shubnikov-de Haas magnetic quantum oscillations. The oscillations display a single frequency F=255±10 T, indicating a small Fermi pocket that is ∼1% of the two-dimensional Brillouin zone and consistent with a Fermi surface reconstructed from the large holelike cylinder predicted for these layered materials.
Evolution of electronic correlations across the rutile, perovskite, and Ruddelsden-Popper iridates with octahedral connectivity
The confluence of electron correlations and spin-orbit interactions is critical to realizing quantum phases in 5d transition metal oxides. Here, we investigate how the strength of the effective electron correlations evolve across a series of d5 iridates comprised of IrO6 octahedra, ranging from the layered correlated insulator Sr2IrO4, to the three-dimensional perovskite semimetal SrIrO3, to metallic rutile IrO2 in which the octahedra are arranged in a mixed edge and corner sharing network.
Scanning SQUID susceptometers with sub-micron spatial resolution
Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz1/2.
Tunable phonon-cavity coupling in graphene membranes
A major achievement of the past decade has been the realization of macroscopic quantum systems by exploiting the interactions between optical cavities and mechanical resonators. In these systems, phonons are coherently annihilated or created in exchange for photons. Similar phenomena have recently been observed through phonon-cavity coupling - energy exchange between the modes of a single system mediated by intrinsic material nonlinearity.
Scaling ansatz for the jamming transition
We propose a Widom-like scaling ansatz for the critical jamming transition. Our ansatz for the elastic energy shows that the scaling of the energy, compressive strain, shear strain, system size, pressure, shear stress, bulk modulus, and shear modulus are all related to each other via scaling relations, with only three independent scaling exponents. We extract the values of these exponents from already known numerical or theoretical results, and we numerically verify the resulting predictions of the scaling theory for the energy and residual shear stress.
Featureless quantum insulator on the honeycomb lattice
We show how to construct fully symmetric states without topological order on a honeycomb lattice for S=12 spins using the language of projected entangled pair states. An explicit example is given for the virtual bond dimension D=4. Four distinct classes differing by lattice quantum numbers are found by applying the systematic classification scheme introduced by two of the authors [S. Jiang and Y. Ran, Phys. Rev. B 92, 104414 (2015)PRBMDO1098-012110.1103/PhysRevB.92.104414].
Gate Tuning of Electronic Phase Transitions in Two-Dimensional NbSe2
Recent experimental advances in atomically thin transition metal dichalcogenide (TMD) metals have unveiled a range of interesting phenomena including the coexistence of charge-density-wave (CDW) order and superconductivity down to the monolayer limit. The atomic thickness of two-dimensional (2D) TMD metals also opens up the possibility for control of these electronic phase transitions by electrostatic gating. Here, we demonstrate reversible tuning of superconductivity and CDW order in model 2D TMD metal NbSe2 by an ionic liquid gate.