A5066230430- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum many-body systems
- Quantum, superfluid, helium dynamics
- Graphene research and applications
- Advancements in Semiconductor Devices and Circuit Design
- Atomic and Subatomic Physics Research
- Advanced Condensed Matter Physics
- Medieval European History and Architecture
- Quantum Information and Cryptography
- Superconducting Materials and Applications
- Quantum Chromodynamics and Particle Interactions
- Surface and Thin Film Phenomena
- Semiconductor Quantum Structures and Devices
- Quantum optics and atomic interactions
- Historical Astronomy and Related Studies
- Particle physics theoretical and experimental studies
- Theoretical and Computational Physics
- Advanced NMR Techniques and Applications
- Historical, Literary, and Cultural Studies
- Maternal and fetal healthcare
- Per- and polyfluoroalkyl substances research
- Muon and positron interactions and applications
University of Kent
2017-2024
University of Cambridge
2009-2017
Cavendish Hospital
2009-2012
University of Colorado Boulder
2011
Laboratoire de Physique Théorique et Modèles Statistiques
2005-2006
Centre National de la Recherche Scientifique
2006
Alcatel Lucent (Germany)
2005
We analyze an array of linearly extended monodomain dipoles forming square and kagome lattices. find that its phase diagram contains two (distinct) finite-entropy ice regimes---one disordered, one algebraic---as well as a low-temperature ordered phase. In the limit islands almost touching, we staircase corresponding entropy plateaux, which is analytically captured by theory based on magnetic charges. For case modified array, show charges (``monopoles'') are excitations experiencing distinct...
We study a frustrated dipolar array recently manufactured lithographically by Wang {\em et al.} [Nature {\bf 439}, 303 (2006)] in order to realize the square ice model an artificial structure. discuss models for thermodynamics and dynamics of this system. show that regime can be stabilized small changes geometry; different magnetic state, kagome ice, similarly constructed. At low temperatures, is terminated thermodynamic ordering transition, which chosen ferro- or antiferromagnetic. arrays...
We study the ground states of Bose-Hubbard model in a uniform magnetic field, motivated by physics cold atomic gases on lattices at high vortex density. Mapping bosons to composite fermions (CF) leads prediction quantum Hall fluids that have no counterpart continuum. construct trial for these phases and test numerically predictions CF model. establish existence strongly correlated beyond those continuum limit provide evidence wider scope fermion approach its application lowest Landau level.
The Harper-Hofstadter model provides a fractal spectrum containing topological bands of any integer Chern number, $C$. We study the many-body physics that is realized by interacting particles occupying with $|C|>1$. formulate predictions Chern-Simons or composite fermion theory in terms filling factor, $\nu$, defined as ratio particle density to number single-particle states per unit area. show this predicts series fractional quantum Hall factors $\nu = r/(r|C| +1)$ for bosons, r/(2r|C|...
We study correlated phases occurring in the flat lowest band of dice-lattice model at flux density one-half. discuss how to realize this model, also referred as T(3) lattice, cold atomic gases. construct projection dice band, which yields a Hubbard Hamiltonian with interaction-assisted hopping processes. solve for bosons two limits. In limit large density, we use Gross-Pitaevskii mean-field theory reveal time-reversal symmetry breaking vortex lattice phases. At low exact diagonalization...
Abstract The fractional quantum Hall (FQH) effect illustrates the range of novel phenomena which can arise in a topologically ordered state presence strong interactions. possibility realizing FQH-like phases models with lattice effects has attracted intense interest as more experimentally accessible venue for FQH calls theoretical attention. Here we investigate physical relevance previously derived geometric conditions quantify deviations from Landau level physics FQHE. We conduct extensive...
We construct a family of BCS paired composite-fermion wave functions that generalize but remain in the same topological phase as Moore-Read Pfaffian state for half-filled Landau level. It is shown wide range experimentally relevant interelectron interactions, ground can be very accurately represented this form.
We show how the phases of interacting particles in topological flat bands, known as fractional Chern insulators, can be adiabatically connected to incompressible quantum Hall liquids lowest Landau level an externally applied magnetic field. Unlike previous evidence suggesting similarity these systems, our approach enables a formal proof equality their orders, and furthermore this robustly extends thermodynamic limit. achieve result using hybrid Wannier orbital basis proposed by Qi [Phys....
We study the stability of composite fermion fractional quantum Hall states in Harper-Hofstadter bands with Chern number $|C|>1$. From theory, are predicted to be found at filling factors $\ensuremath{\nu}=r/(kr|C|+1),r\ensuremath{\in}\mathbb{Z}$, $k=1$ for bosons and $k=2$ fermions. Here, we closely analyze these series both cases, contact interactions nearest-neighbor (spinless) In particular, how many-body gap scales as tuned effective continuum limit $|C|$ bands, realized near flux...
The Hofstadter model is a popular choice for theorists investigating the fractional quantum Hall effect on lattices, due to its simplicity, infinite selection of topological flat bands, and increasing applicability real materials. In particular, Chern insulators in bands with number $|C|>1$ can demonstrate richer physical properties than continuum Landau level states have recently been detected experiments. Motivated by this, we examine stability higher model, using large-scale density...
We study theoretically the ground states of two-dimensional Bose-Hubbard models which are frustrated by gauge fields. Motivated recent proposals for implementation optically induced potentials, we focus on situation in imposed fields give rise to a pattern staggered fluxes magnitude $\ensuremath{\alpha}$ and alternating sign along one principal axes. For $\ensuremath{\alpha}=1/2$ this model is equivalent case uniform flux per plaquette ${n}_{\ensuremath{\phi}}=1/2$, which, hard-core limit,...
We study interacting bosons on a lattice in magnetic field. When the number of flux quanta per plaquette is close to rational fraction, low energy physics mapped multi-species continuum model: lowest Landau level where each boson given an internal degree freedom, or pseudospin. find that interaction potential between involves terms do not conserve pseudospin, corresponding umklapp processes, which some cases can also be seen as BCS-type pairing terms. argue experimentally realistic regimes...
The study of magnetic correlations in dipolar-coupled nanomagnet systems with synchrotron x-ray scattering provides a means to uncover emergent phenomena and exotic phases, particular thermally active moments. From the diffuse signal soft resonant scattering, we have measured highly dynamic artificial kagome spin ice sub-70-nm Permalloy nanomagnets. On comparing experimental patterns Monte Carlo simulations based on needle-dipole model, conclude that I phase exist our system even presence...
In three-dimensional space an electron moving in the field of a magnetic monopole has no bound states. this paper we explore physics when is restricted to two-dimensional plane adjacent monopole. We find states classical version problem and quasi-bound quantum one, addition continuum scattering calculate lifetimes using several complementary approximate methods, which agree well cases where are relatively short. The threshold charge required realise single state approximately $18Q_D$, $Q_D$...
We provide numerical evidence for composite fermion pairing in quantum Hall bilayer systems at filling nu=1/2+1/2 intermediate spacing between the layers. identify phase as p_(x)+ip_(y) pairing, and construct high accuracy trial wave functions to describe ground state on sphere. For large distances layers, finite systems, a competing "Hund's rule" state, or liquid, prevails certain system sizes.
Quantum Hall bilayer systems at filling fractions near $\ensuremath{\nu}=\frac{1}{2}+\frac{1}{2}$ undergo a transition from compressible phase with strong intralayer correlation to an incompressible interlayer correlations as the layer separation $d$ is reduced below some critical value. Deep in (large separation) system can be interpreted fluid of composite fermions (CFs), whereas deep (small bosons (CBs). The focus this paper understand states that occur for intermediate by using trial...
We present evidence supporting the weakly paired Moore-Read phase in half-filled second Landau level, focusing on some of qualitative features its excitations. Based numerical studies, we show that systems with odd particle number at flux N(ϕ)=2N-3 can be interpreted as a neutral fermion mode one unpaired fermion, which is gapped. The found to have two distinct minima, providing signature could observed by photoluminescence. In presence quasiparticles same excitation shown gapless,...
We use particle entanglement spectra to characterize bosonic quantum Hall states on lattices, motivated by recent studies of atoms optical lattices. Unlike for the related problem fractional Chern insulators, very good trial wavefunctions are known focus Laughlin state at $\nu=1/2$ non-Abelian Moore-Read $\nu=1$. undertake a comparative study these corresponding groundstates repulsive two-body or three-body contact interactions lattice. The magnitude gap is studied as function interaction...
We provide numerical evidence that a p_{x}-i p_{y} paired Bonderson--Slingerland (BS) non-Abelian hierarchy state is strong candidate for the observed nu=12/5 quantum Hall plateau. confirm existence of gapped incompressible nu = 12/5 with shift S=2 on sphere, matching BS state. The exact ground Coulomb interaction at shown to have large overlap trial wave function. Larger overlaps are obtained BS-type functions hierarchical descendants general weakly-paired states nu=5/2. perform finite size...
TeNPy (short for ‘Tensor Network Python’) is a python library the simulation of strongly correlated quantum systems with tensor networks. The philosophy this to achieve balance readability and usability new-comers, while at same time providing powerful algorithms experts. focus on MPS 1D 2D lattices, such as DMRG ground state search, well dynamics using TEBD, TDVP, or MPO evolution. This article companion recent version 1.0 release gives brief overview package.
The method of Jain and Kamilla [J. K. R. Kamilla, Phys. Rev. B 55, R4895 (1997)] allows numerical generation composite-fermion trial wave functions for large numbers electrons in high magnetic fields at filling fractions the form $\ensuremath{\nu}=p∕(2mp+1)$ with $m$ $p$ positive integers. In current paper we generalize this to case where composite fermions are an effective (mean) field opposite sign from actual physical field, i.e., when is negative. We examine both ground-state energies...
We investigate, with the help of Monte Carlo and exact-diagonalization calculations in spherical geometry, several compressible incompressible candidate wave functions for recently observed quantum Hall state at filling factor $\ensuremath{\nu}=1/4$ a wide well. The well is modeled as two-component system by retaining its two lowest subbands. make direct connection phenomenological effective-bilayer model, which commonly used description we compare our findings established results...
We study charged excitations of the non-Abelian Moore-Read liquid at a filling factor nu=5/2, allowing for spin depolarization. Using combination numerical studies, and taking account nonzero well widths, we find that sufficiently low Zeeman energy it is energetically favorable charge e/4 quasiholes to bind into Skyrmions e/2. show Skyrmion formation further promoted by disorder, argue this can lead depolarized nu=5/2 ground state in realistic experimental situations. comment on consequences...