A5057538064- Topological Materials and Phenomena
- Advanced Condensed Matter Physics
- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Quantum many-body systems
- Magnetic and transport properties of perovskites and related materials
- Cold Atom Physics and Bose-Einstein Condensates
- Graphene research and applications
- Surface and Thin Film Phenomena
- Electronic and Structural Properties of Oxides
- Magnetic properties of thin films
- 2D Materials and Applications
- Theoretical and Computational Physics
- Advancements in Semiconductor Devices and Circuit Design
- Advanced Thermoelectric Materials and Devices
- Multiferroics and related materials
- Quantum, superfluid, helium dynamics
- Advanced Chemical Physics Studies
- Nuclear materials and radiation effects
- Semiconductor Quantum Structures and Devices
- Plasmonic and Surface Plasmon Research
- Quantum optics and atomic interactions
- Atomic and Subatomic Physics Research
- ZnO doping and properties
- Mechanical and Optical Resonators
Northeastern University
2019-2025
Massachusetts Institute of Technology
2018-2025
Universidad del Noreste
2024-2025
IIT@MIT
2024
The University of Texas at Austin
2011-2020
California Institute of Technology
2007-2009
University of California, Santa Barbara
2003-2008
Harvard University
2002-2006
Argonne National Laboratory
2003-2005
Freie Universität Berlin
2005
Chirally stacked $N$-layer graphene systems with $N\ensuremath{\ge}2$ exhibit a variety of distinct broken symmetry states in which charge density contributions from different spins and valleys are spontaneously transferred between layers. We explain how these distinguished by their charge, spin, valley Hall conductivities, orbital magnetizations, edge state properties. argue that have [$N/2$] channels per spin valley.
Abstract The Materials Genome Initiative (MGI) advanced a new paradigm for materials discovery and design, namely that the pace of deployment could be accelerated through complementary efforts in theory, computation, experiment. Along with numerous successes, challenges are inviting researchers to refocus approaches were originally inspired by MGI. In May 2017, National Science Foundation sponsored workshop “Advancing Accelerating Innovation Through Synergistic Interaction among Computation,...
We study the electronic contribution to thermal conductivity and thermopower of Weyl Dirac semimetals using a semiclassical Boltzmann approach. investigate effect various relaxation processes including disorder interactions on thermoelectric properties, also consider doping away from or point. find that have an interesting dependence chemical potential is characteristic linear dispersion, electron-electron modify Lorenz number. For interacting system, we use Kubo formalism obtain transport...
Abstract Symmetry-protected topological crystalline insulators (TCIs) have primarily been characterized by their gapless boundary states. However, in time-reversal- ( $${{{{{{{\mathcal{T}}}}}}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>T</mml:mi> </mml:math> -) invariant (helical) 3D TCIs—termed higher-order TCIs (HOTIs)—the signatures can manifest as a sample-dependent network of 1D hinge We here introduce nested spin-resolved Wilson loops and layer constructions...
Circularly polarized lattice vibrations, also known as chiral phonons, carry angular momentum that leads to magnetic response. Recent experiments revealed responses far exceeding prior theoretical predictions within a classical framework. Here, the authors introduce microscopic model which explains large moments of phonons in materials, resulting from orbit-lattice couplings hybridize optical with orbital electronic transitions.
Quantum corrals are two dimensional structures built atom by on an atomically clean metallic surface using a scanning tunneling microscope. These ``corral'' electrons in the states of noble metals which lead to standing wave patterns electron density inside quantum corral. We review physics and relate signal microscope scattering properties substrate from atomic impurities supported surface. The theory includes effects incoherent state at quantitively describes all current STM data corrals,...
We study the spinless and spinful extended Hubbard models with repulsive interactions on kagome decorated honeycomb (star) lattice. Using Hartree-Fock mean-field theory, we show that interaction-driven insulating phases nontrivial topological invariants (Chern number or ${Z}_{2}$ invariant) exist for an experimentally reasonable range of parameters. These occur at filling fractions which involve either Dirac points quadratic band crossing in noninteracting limit. present comprehensive phase...
Topological band insulators which are dynamically generated by electron-electron interactions have been theoretically proposed in two- and three-dimensional lattice models. We present evidence that the two-dimensional version can be stabilized digital (111) heterostructures of transition-metal oxides as a result purely local interactions. The topological phases accompanied spontaneous ordering complex orbitals we discuss their stability with respect to Hund's rule coupling, Jahn-Teller...
We theoretically study magnetic and topological properties of antiferromagnetic kagome spin systems in the presence both in- out-of-plane Dzyaloshinskii-Moriya interactions. In materials such as iron jarosites, in-plane interactions stabilize a canted noncollinear ``umbrella'' configuration with finite scalar chirality. derive expressions for canting angle use resulting order starting point spin-wave analysis. find magnon bands, characterized by nonzero Chern numbers. calculate thermal Hall...
PbTe crystals have a soft transverse optical phonon mode in the terahertz frequency range, which is known to efficiently decay into heat-carrying acoustic phonons, resulting anomalously low thermal conductivity. Here, we studied this via polarization-dependent spectroscopy. We observed softening of with decreasing temperature, indicative incipient ferroelectricity, explain through model including strong anharmonicity quartic displacement term. In magnetic fields up 25 T, splits two modes...
The recently demonstrated chiral modes of lattice motion carry angular momentum and therefore directly couple to magnetic fields. Notably, their moments are predicted be strongly influenced by electronic contributions. Here, we have studied the response transverse optical phonons in a set Pb 1− x Sn Te films, which is topological crystalline insulator for > 0.32 has ferroelectric transition at an -dependent critical temperature. Polarization-dependent terahertz magnetospectroscopy...
The interplay of charge, spin, lattice, and orbital degrees freedom in correlated materials often leads to rich exotic properties. Recent studies have brought new perspectives bosonic collective excitations materials. For example, inelastic neutron scattering experiments revealed non-trivial band topology for magnons spin–orbit excitons (SOEs) a quantum magnet CoTiO 3 (CTO). Here, we report phonon properties resulting from combination strong coupling, large crystal field splitting, trigonal...
Because of the lack a net magnetic moment, antiferromagnets possess unique robustness to external fields and are thus predicted play an important role in future technologies. However, this also makes them quite difficult control, development novel methods manipulate these systems with stimuli is fundamental goal antiferromagnetic spintronics. In work, we report evidence for metastable reorientation order parameter semiconductor triggered by ultrafast quench equilibrium via photoexcitation...
In contrast to the well known Fermi liquid theory of three dimensions, interacting one-dimensional and quasi systems fermions are described at low energy by an effective as Luttinger theory. This is expressed in terms collective many-body excitations that show exotic behavior such spin-charge separation. commonly applied on premise "low energy" describes both spin charge sectors. However, when interactions system very strong, they typically particle densities, ratio may become exponentially...
In this work we investigate the phase diagram of heavy (4d and 5d) transition metal oxides on pyrochlore lattice, such as those form $\mathrm{A_2M_2O_7}$, where A is a rare earth element M element. We focus competition between Coulomb interaction, spin-orbit coupling, lattice distortion when these energy scales are comparable. Strong coupling entangles spin $t_{2g}$ $d$-orbitals giving rise to doublet $j=1/2$ quadruplet $j=3/2$ states. contrast previous works which focused manifold, also...
We study a tight-binding model on the two-dimensional ruby lattice. This lattice supports several types of first and second neighbor spin-dependent hopping parameters in an $s$-band that preserves time-reversal symmetry. discuss phase diagram this for various values filling fractions, note interesting competition between spin-orbit terms individually would drive system to $Z_2$ topological insulating phase. also closely related spin-polarized with only hoppings show extremely flat bands...
Topological crystalline insulators possess electronic states protected by crystal symmetries, rather than time-reversal symmetry. We show that the transition metal oxides with heavy metals are able to support nontrivial band topology resulting from mirror symmetry of lattice. As an example, we consider pyrochlore form A2M2O7. a function spin-orbit coupling strength, find two Z2 topological insulator phases can be distinguished each other their Chern numbers, indicating different insulators....
We provide a self-consistent mean-field framework to study the effect of strong interactions in quantum spin Hall insulator on honeycomb lattice. identify an exotic phase for large spin-orbit coupling and intermediate Hubbard interaction. This is gapped does not break any symmetry. Instead, we find fourfold topological degeneracy ground state torus fractionalized excitations with semionic mutual braiding statistics. Moreover, argue that it has gapless edge modes protected by time-reversal...
We theoretically investigate a tight binding model of fermions hopping on the square-octagon lattice which consists square with plaquette corners themselves decorated by squares. Upon inclusion second neighbor spin-orbit coupling or non-Abelian gauge fields, time-reversal symmetric topological Z_2 band insulators are realized. Additional insulating and gapless phases also realized via fields. Some phase transitions involve changes to Fermi surface. The stability various symmetry breaking...
We study the thermoelectric properties of a double-Weyl fermion system, possibly realized in ${\mathrm{HgCr}}_{2}{\mathrm{Se}}_{4}$ and ${\mathrm{SrSi}}_{2}$, by semiclassical Boltzmann transport theory. investigate different relaxation processes including short-range disorder electron-electron interaction on coefficients. It is found that anisotropy band dispersion for in-plane out-of-plane momentum directions affects time directions. The also exhibits an interesting directional dependence...