Institutions

About Us

Help

Gaeilge
0
1000
Home
Browse
Advanced Search
Search History
Marked List
Statistics
A
A
A
Author(s)
Institution
Publication types
Funder
Year
Limited By:
Author = EASTHAM, PAUL;
46 items found
Sort by
Title
Author
Item type
Date
Institution
Peer review status
Language
Order
Ascending
Descending
25
50
100
per page
1
2
Bibtex
CSV
EndNote
RefWorks
RIS
XML
Displaying Results 26  46 of 46 on page 2 of 2
Marked
Mark
Models of coherent exciton condensation
(2004)
EASTHAM, PAUL
Models of coherent exciton condensation
(2004)
EASTHAM, PAUL
Abstract:
That excitons in solids might condense into a phasecoherent ground state was proposed about 40 years ago, and has been attracting experimental and theoretical attention ever since. Although experimental confirmation has been hard to come by, the concepts released by this phenomenon have been widely influential. This tutorial review discusses general aspects of the theory of exciton and polariton condensates, focussing on the reasons for coherence in the ground state wavefunction, the BCS to Bose crossover(s) for excitons and for polaritons, and the relationship of the coherent condensates to standard lasers.
http://hdl.handle.net/2262/49386
Marked
Mark
Nearfield relaxation of a quantum emitter to 2D semiconductors: surface dissipation and exciton polaritons
(2016)
Eastham, Paul; Bradley, Louise; Karanikolas, Vasilios D.; Marocico, Cristian A.
Nearfield relaxation of a quantum emitter to 2D semiconductors: surface dissipation and exciton polaritons
(2016)
Eastham, Paul; Bradley, Louise; Karanikolas, Vasilios D.; Marocico, Cristian A.
Abstract:
The total spontaneous emission rate of a quantum emitter in the presence of an infinite MoS2 monolayer is enhanced by several orders of magnitude, compared to its freespace value, due to the excitation of surface exciton polariton modes and lossy modes. The spectral and distance dependence of the spontaneous emission rate are analyzed and the lossy surface wave, surface exciton polariton mode and radiative contributions are identified. The transverse magnetic and transverse electric exciton polariton modes can be excited for different emission frequencies of the quantum emitter, and their contributions to the total spontaneous emission rate are different. To calculate these different decay rates we use the nonHermitian description of lightmatter interactions, employing a Green's tensor formalism. The distance dependence follows different trends depending on the emission energy of the quantum emitter. For the case of the lossy surface waves, the distance dependence follows a ...
http://hdl.handle.net/2262/91750
Marked
Mark
Parametric relaxation in whispering gallery mode excitonpolariton condensates
(2015)
EASTHAM, PAUL
Parametric relaxation in whispering gallery mode excitonpolariton condensates
(2015)
EASTHAM, PAUL
http://hdl.handle.net/2262/73020
Marked
Mark
Phaselocking in quantum and classical oscillators: polariton condensates, lasers, and arrays of Josephson junctions
(2003)
EASTHAM, PAUL
Phaselocking in quantum and classical oscillators: polariton condensates, lasers, and arrays of Josephson junctions
(2003)
EASTHAM, PAUL
Abstract:
We connect three phenomena in which a coherent electromagnetic field could be generated: polariton condensation, phaselocking in arrays of underdamped Josephson junctions, and lasing. All these phenomena have been described using Dicketype models of spins coupled to a single photon mode. These descriptions may be distinguished by whether the spins are quantum or classical, and whether they are strongly or weakly damped.
http://hdl.handle.net/2262/49387
Marked
Mark
Polariton condensation with localized excitons and propagating photons
(2004)
EASTHAM, PAUL
Polariton condensation with localized excitons and propagating photons
(2004)
EASTHAM, PAUL
Abstract:
We estimate the condensation temperature for microcavity polaritons, allowing for their internal structure. We consider polaritons formed from localized excitons in a planar microcavity, using a generalized Dicke model. At low densities, we find a condensation temperature Tc / , as expected for a gas of structureless polaritons. However, as Tc becomes of the order of the Rabi splitting, the structure of the polaritons becomes relevant, and the condensation temperature is that of a BCSlike meanfield theory.We also calculate the excitation spectrum, which is related to observable quantities such as the luminescence and absorption spectra.
http://hdl.handle.net/2262/49385
Marked
Mark
Population inversion in a single InGaAs quantum dot using the method of adiabatic rapid passage
(2011)
EASTHAM, PAUL
Population inversion in a single InGaAs quantum dot using the method of adiabatic rapid passage
(2011)
EASTHAM, PAUL
Abstract:
Preparation of a speci c quantum state is a required step for a variety of proposed practical uses of quantum dynamics. We report an experimental demonstration of optical quantum state preparation in a semiconductor quantum dot with electrical readout, which contrasts with earlier work based on Rabi opping in that the method is robust with respect to variation in the optical coupling. We use adiabatic rapid passage, which is capable of inverting single dots to a speci ed upper level. We demonstrate that when the pulse power exceeds a threshold for inversion, the nal state is independent of power. This provides a new
http://hdl.handle.net/2262/49584
Marked
Mark
Population inversion in quantum dot ensembles via adiabatic rapid passage
(2010)
EASTHAM, PAUL
Population inversion in quantum dot ensembles via adiabatic rapid passage
(2010)
EASTHAM, PAUL
Abstract:
Electrical detection of adiabatic rapid passage (ARP) in quantum dot ensembles is explored by extension of a simple physical model. We include exciton and biexciton states and model the current flow into the external circuit which occurs following ionization of the exciton and tunneling of the separate carriers. The inversion produced by ARP is robust with respect to fluctuations in coupling and detuning, and we show directly that this manifests itself as only minor variation in the current drawn per dot, as the number of dots in an ensemble is increased. This approach therefore can provide a means of initializing many dots simultaneously into a specific excited state.
http://hdl.handle.net/2262/40211
Marked
Mark
Quantum condensation from a tailored exciton population in a microcavity
(2009)
EASTHAM, PAUL
Quantum condensation from a tailored exciton population in a microcavity
(2009)
EASTHAM, PAUL
Abstract:
An experiment is proposed on the coherent quantum dynamics of a semiconductor microcavity containing quantum dots. Modeling the experiment using a generalized Dicke model, we show that a tailored excitation pulse can create an energydependent population of excitons, which subsequently evolves to a quantum condensate of excitons and photons. The population is created by a generalization of adiabatic rapid passage and then condenses due to a dynamical analog of the BCS instability.
http://hdl.handle.net/2262/49589
Marked
Mark
Quantum control of excitons for reversible heat transfer
(2019)
Eastham, Paul
Quantum control of excitons for reversible heat transfer
(2019)
Eastham, Paul
Abstract:
Lasers, photovoltaics, and thermoelectricallypumped light emitting diodes are thermodynamic machines which use excitons (electronhole pairs) as the working medium. The heat transfers in such devices are highly irreversible, leading to low efficiencies. Here we predict that reversible heat transfers between a quantumdot exciton and its phonon environment can be induced by laser pulses. We calculate the heat transfer when a quantumdot exciton is driven by a chirped laser pulse. The reversibility of this heat transfer is quantified by the efficiency of a heat engine in which it forms the hot stroke, which we predict to reach 95% of the Carnot limit. This performance is achieved by using the timedependent laserdressing of the exciton to control the heat current and exciton temperature. We conclude that reversible heat transfers can be achieved in excitonic thermal machines, allowing substantial improvements in their efficiency.
http://hdl.handle.net/2262/89660
Marked
Mark
Quantum corrections to the Ising interactions in LiYxHo1xF4
(2008)
EASTHAM, PAUL
Quantum corrections to the Ising interactions in LiYxHo1xF4
(2008)
EASTHAM, PAUL
Abstract:
We systematically derive an effective Hamiltonian for the dipolar magnet LiY1?xHoxF4, including quantum corrections which arise from the transverse dipolar and hyperfine interactions. These corrections are derived using a generalised SchriefferWolff transformation to leading order in the small parameters given by the ratio of the interaction energies to the energy of the first excited electronic state of the Holmium ions. The resulting lowenergy Hamiltonian involves twolevel systems, corresponding to the lowlying electronic states of the Holmiums, which are coupled to one another and to the Holmium nuclei. It differs from that obtained by treating the electronic states of the Holmium as a spin1/2 with an anisotropic gfactor. It includes effective onsite transverse fields, and both pairwise and threebody interactions among the dipoles and nuclei. We explain the origins of the terms, and give numerical values for their strengths.
http://hdl.handle.net/2262/49378
Marked
Mark
Quantum theory of multimode polariton condensation
(2014)
EASTHAM, PAUL
Quantum theory of multimode polariton condensation
(2014)
EASTHAM, PAUL
Abstract:
We develop a theory for the dynamics of the density matrix describing a multimode polariton condensate. In such a condensate several singleparticle orbitals become highly occupied, due to stimulated scattering from reservoirs of highenergy excitons. A generic fewparameter model for the system leads to a Lindblad equation which includes saturable pumping, decay, and condensate interactions. We show how this theory can be used to obtain the population distributions, and the timedependent first and secondorder coherence functions, in such a multimode condensate. As a specific application, we consider a polaritonic Josephson junction, formed from a doublewell potential. We obtain the population distributions, emission line shapes, and widths (firstorder coherence functions), and predict the dephasing time of the Josephson oscillations.
http://hdl.handle.net/2262/71220
Marked
Mark
Robust Optical Inversion of the Excitonic Population of InGaAs Quantum Dots via Adiabatic Rapid Passage
(2011)
EASTHAM, PAUL
Robust Optical Inversion of the Excitonic Population of InGaAs Quantum Dots via Adiabatic Rapid Passage
(2011)
EASTHAM, PAUL
Abstract:
We show population inversion in a semiconductor quantum dot with a chirped optical pulse via adiabatic rapid passage. This method is insensitive to variations in the dipole coupling and provides a new tool for preparing ensembles of quantum states.
http://hdl.handle.net/2262/56903
Marked
Mark
Steady states of a chi(3) parametric oscillator with coupled polarizations
(2003)
EASTHAM, PAUL
Steady states of a chi(3) parametric oscillator with coupled polarizations
(2003)
EASTHAM, PAUL
Abstract:
Polarization effects in the microcavity parametric oscillator are studied using a simple model in which two x3 optical parametric oscillators are coupled together. It is found that there are, in general, a number of steady states of the model under continuous pumping. There are both continuous and discontinuous thresholds, at which new steady states appear as the driving intensity is increased: at the continuous thresholds, the new state has zero output intensity, whereas at the discontinuous threshold it has a finite output intensity. The discontinuous thresholds have no analog in the uncoupled device. The coupling also generates rotations of the linear polarization of the output compared with the pump, and shifts in the output frequencies as the driving polarization or intensity is varied. For large ratios of the interaction between polarizations to the interaction within polarizations, of the order of 5, one of the thresholds has its lowest value when the pump is elliptically pol...
http://hdl.handle.net/2262/49388
Marked
Mark
Stimulated spin dynamics of polaritons in semiconductor microcavities
(2002)
EASTHAM, PAUL
Stimulated spin dynamics of polaritons in semiconductor microcavities
(2002)
EASTHAM, PAUL
Abstract:
Timeresolved polarization spectroscopy of polariton pair scattering in semiconductor microcavities enables complete measurement of the polariton spin dynamics. In addition to spinpreserving interactions previously reported, we observe two additional even stronger scattering processes, which mix polaritons of opposite spin. Because of the polaritons? bosonic character, this results in the stimulation of spin flips. Such mechanisms should allow realization of spinsensitive interferometers.
http://hdl.handle.net/2262/49389
Marked
Mark
Superfluid stiffness of a driven dissipative condensate with disorder
(2013)
EASTHAM, PAUL
Superfluid stiffness of a driven dissipative condensate with disorder
(2013)
EASTHAM, PAUL
http://hdl.handle.net/2262/69201
Marked
Mark
Synchronization crossover of polariton condensates in weakly disordered lattices
(2018)
Eastham, Paul
Synchronization crossover of polariton condensates in weakly disordered lattices
(2018)
Eastham, Paul
http://hdl.handle.net/2262/83986
Marked
Mark
The creation and annihilation of optical vortices using cascade conical diffraction
(2011)
LUNNEY, JAMES; DONEGAN, JOHN; PHELAN, CIARAN; RAKOVICH, YURY; EASTHAM, PAUL
The creation and annihilation of optical vortices using cascade conical diffraction
(2011)
LUNNEY, JAMES; DONEGAN, JOHN; PHELAN, CIARAN; RAKOVICH, YURY; EASTHAM, PAUL
Abstract:
Internal conical diffraction produces a superposition of orthogonally polarised zero and firstorder Bessel like beams from an incident circularly polarised Gaussian beam. For rightcircularly polarised light, the firstorder beam has an optical vortex of charge ?1. Upon propagation of the firstorder beam through a second biaxial crystal, a process which is termed cascade conical refraction, the generated beam is a superposition of orthogonally polarised fields of charge 0 and ?1 or 0 and ?2. This spin to orbital angular momentum conversion provides a new method for the generation and annihilation of optical vortices in an alloptical arrangement that is solely dependent on the incident polarisation and vortex handedness.
http://hdl.handle.net/2262/50582
Marked
Mark
The new physics of nonequilibrium condensates: insights from classical dynamics
(2007)
EASTHAM, PAUL
The new physics of nonequilibrium condensates: insights from classical dynamics
(2007)
EASTHAM, PAUL
Abstract:
We discuss the dynamics of classical Dicketype models, aiming to clarify the mechanisms by which coherent states could develop in potentially nonequilibrium systems such as semiconductor microcavities. We present simulations of an undamped model which show spontaneous coherent states with persistent oscillations in the magnitude of the order parameter. These states are generalisations of superradiant ringing to the case of inhomogeneous broadening. They correspond to the persistent gap oscillations proposed in fermionic atomic condensates, and arise from a variety of initial conditions. We show that introducing randomness into the couplings can suppress the oscillations, leading to a limiting dynamics with a timeindependent order parameter. This demonstrates that nonequilibrium generalisations of polariton condensates can be created even without dissipation. We explain the dynamical origins of the coherence in terms of instabilities of the normal state, and consider how it can a...
http://hdl.handle.net/2262/49379
Marked
Mark
There are many ways to spin a photon: Halfquantization of a total optical angular momentum
(2016)
EASTHAM, PAUL; DONEGAN, JOHN; Ballantine, Kyle E.
There are many ways to spin a photon: Halfquantization of a total optical angular momentum
(2016)
EASTHAM, PAUL; DONEGAN, JOHN; Ballantine, Kyle E.
Abstract:
The angular momentum of light plays an important role in many areas, from optical trapping to quantum information. In the usual threedimensional setting, the angular momentum quantum numbers of the photon are integers, in units of the Planck constant ħ. We show that, in reduced dimensions, photons can have a halfinteger total angular momentum. We identify a new form of total angular momentum, carried by beams of light, comprising an unequal mixture of spin and orbital contributions. We demonstrate the halfinteger quantization of this total angular momentum using noise measurements. We conclude that for light, as is known for electrons, reduced dimensionality allows new forms of quantization.
http://hdl.handle.net/2262/91748
Marked
Mark
Vortex states of a disordered quantum Hall bilayer
(2009)
EASTHAM, PAUL
Vortex states of a disordered quantum Hall bilayer
(2009)
EASTHAM, PAUL
Abstract:
We present and solve a model for the vortex configuration of a disordered quantum Hall bilayer in the limit of strong and smooth disorder. We argue that there is a characteristic disorder strength below which vortices will be rare and above which they proliferate. We predict that this can be observed tuning the electron density in a given sample. The ground state in the strongdisorder regime can be understood as an emulsion of vortexantivortex crystals. Its signatures include a suppression of the spatial decay of counterflow currents. We find an increase of at least an order of magnitude in the length scale for this decay compared to a clean system. This provides a possible explanation of the apparent absence of leakage of counterflow currents through interlayer tunneling, even in experiments performed deep in the coherent phase where enhanced interlayer tunneling is observed.
http://hdl.handle.net/2262/49588
Marked
Mark
White light conical diffraction
(2013)
BALLANTINE, KYLE EDWARD; MC CLOSKEY, DAVID; JENNINGS, BRIAN DAVID; LUNNEY, JAMES GERARD...
White light conical diffraction
(2013)
BALLANTINE, KYLE EDWARD; MC CLOSKEY, DAVID; JENNINGS, BRIAN DAVID; LUNNEY, JAMES GERARD; DARCY, RONAN; DONEGAN, JOHN FRANCIS; EASTHAM, PAUL
http://hdl.handle.net/2262/69262
Displaying Results 26  46 of 46 on page 2 of 2
1
2
Bibtex
CSV
EndNote
RefWorks
RIS
XML
Item Type
Book chapter (1)
Conference item (3)
Journal article (42)
Year
2019 (1)
2018 (3)
2016 (2)
2015 (1)
2014 (3)
2013 (3)
2012 (5)
2011 (5)
2010 (5)
2009 (3)
2008 (3)
2007 (1)
2006 (2)
2005 (2)
2004 (2)
2003 (2)
2002 (1)
2001 (1)
2000 (1)
built by Enovation Solutions