210 citations · 711 across the 17 of their papers we have counts for
18 papers
Tuneable terahertz transitions in zigzag graphene nanoribbons
R. R. Hartmann, M. E. Portnoi
We show that a transverse electric field applied to a zigzag graphene nanoribbon opens a band gap whose energy can be tuned through the terahertz (THz) range. The field breaks the…
Designer gapped and tilted Dirac cones in lateral graphene superlattices
A. Wild, R. R. Hartmann, E. Mariani +1
We show that a planar array of bipolar waveguides in graphene can be used to engineer gapped and tilted two-dimensional Dirac cones within the electronic band structure. The presen…
Polarization-sensitive photoluminescence from aligned carbon chains terminated by gold clusters
A. Kucherik, A. Osipov, V. Samyshkin +3
We synthesize a thin film composed of long carbyne chains terminated by gold clusters and study its optical properties. The presence of gold particles stabilizes longer chains and…
Tuning terahertz transitions in cyclo[n]carbon rings
R. A. Ng, M. E. Portnoi, R. R. Hartmann
We develop an analytic model for an ideal polyyne ring which describes the induced THz gap in the molecular spectrum due to the Stark effect. This simple model can also be used to…
Mapping borophene onto graphene: Quasi-exact solutions for guiding potentials in tilted Dirac cones
R. A. Ng, A. Wild, M. E. Portnoi +1
We show that if the solutions to the (2+1)-dimensional massless Dirac equation for a given 1D potential are known, then they can be used to obtain the eigenvalues and eigenfunction…
Terahertz transitions in finite carbon chains
R. R. Hartmann, S. Kutrovskaya, A. Kucherik +2
We predict an optical effect associated with systems which exhibit topologically protected states separated by a finite distance. We develop a tight-binding model to calculate the…
Guided modes and terahertz transitions for two-dimensional Dirac fermions in a smooth double-well potential
R. R. Hartmann, M. E. Portnoi
The double-well problem for the two-dimensional Dirac equation is solved for a family of quasi-one-dimensional potentials in terms of confluent Heun functions. We demonstrate that…
Bipolar electron waveguides in graphene
R. R. Hartmann, M. E. Portnoi
We show analytically that the ability of Dirac materials to localize an electron in both a barrier and a well can be utilized to open a pseudo-gap in graphene's spectrum. By using…
Excitonic fine structure in emission of linear carbon chains
Stella Kutrovskaya, Anton Osipov, Stepan Baryshev +11
We studied monoatomic linear carbon chains stabilised by gold nanoparticles attached to their ends and deposited on a solid substrate. We observe spectral features of straight chai…
Interband transitions in narrow-gap carbon nanotubes and graphene nanoribbons
R. R. Hartmann, V. A. Saroka, M. E. Portnoi
We use the robust nearest-neighbour tight-binding approximation to study on the same footing interband dipole transitions in narrow-bandgap carbon nanotubes and graphene nanoribbon…
Momentum alignment and the optical valley Hall effect in low-dimensional Dirac materials
V. A. Saroka, R. R. Hartmann, M. E. Portnoi
We study the momentum alignment of photoexcited carriers and the optical control of valley population in gapless and gapped two-dimensional Dirac materials. The trigonal warping ef…
Two-dimensional Dirac particles in a Pöschl-Teller waveguide
R. R. Hartmann, M. E. Portnoi
We obtain exact solutions to the two-dimensional (2D) Dirac equation for the one-dimensional Pöschl-Teller potential which contains an asymmetry term. The eigenfunctions are expres…
Pair states in one-dimensional Dirac systems
R. R. Hartmann, M. E. Portnoi
Analytic solutions of the quantum relativistic two-body problem are obtained for an interaction potential modeled as a one-dimensional smooth square well. Both stationary and movin…
Two-phonon scattering in graphene in the quantum Hall regime
A. M. Alexeev, R. R. Hartmann, M. E. Portnoi
One of the most distinctive features of graphene is its huge inter-Landau-level splitting in experimentally attainable magnetic fields which results in the room-temperature quantum…
Terahertz Science and Technology of Carbon Nanomaterials
R. R. Hartmann, J. Kono, M. E. Portnoi
The diverse applications of terahertz radiation and its importance to fundamental science makes finding ways to generate, manipulate, and detect terahertz radiation one of the key…
Quasi-exact solution to the Dirac equation for the hyperbolic secant potential
R. R. Hartmann, M. E. Portnoi
We analyze bound modes of two-dimensional massless Dirac fermions confined within a hyperbolic secant potential, which provides a good fit for potential profiles of existing top-ga…
Excitons in narrow-gap carbon nanotubes
R. R. Hartmann, I. A. Shelykh, M. E. Portnoi
We calculate the exciton binding energy in single-walled carbon nanotubes with narrow band gaps, accounting for the quasi-relativistic dispersion of electrons and holes. Exact anal…
Smooth electron waveguides in graphene
R. R. Hartmann, N. J. Robinson, M. E. Portnoi
We present exact analytical solutions for the zero-energy modes of two-dimensional massless Dirac fermions fully confined within a smooth one-dimensional potential V(x)= - α/cosh(β…