scholarly journals Switching off microcavity polariton condensate near the exceptional point

2021 ◽  
Author(s):  
Yao Li ◽  
Xuekai Ma ◽  
Zacharias Hatzopoulos ◽  
Pavlos Savvidis ◽  
Stefan Schumacher ◽  
...  
Keyword(s):  
Optical Excitation ◽  
Exceptional Point ◽  
Condensation Process ◽  
Potential Well ◽  
Many Body ◽  
Potential Wells ◽  
Potential Structure ◽  
Gain And Loss ◽  
Double Well Potential ◽  
Additional Loss

Abstract Gain and loss modulation are ubiquitous in nature. An exceptional point arises when both the eigenvectors and eigenvalues coalesce, which in a physical system can be achieved by engineering the gain and loss coefficients, leading to a wide variety of counter-intuitive phenomena. In this work we demonstrate the existence of an exceptional point in an exciton polariton condensate in a double-well potential. Remarkably, near the exceptional point, the polariton condensate localized in one potential well can be switched off by an additional optical excitation in the other well with very low (far below threshold) laser power which surprisingly induces additional loss into the system. Increasing the power of the additional laser leads to a situation in which gain dominates in both wells again, such that the polaritons re-condense with almost the same density in the two potential wells. Our results offer a simple way to optically manipulate the polariton condensation process in a double-well potential structure. Extending such configuration to complex potential well lattices offers exciting prospects to explore high-order exceptional points and non-Hermitian topological photonics in a non-equilibrium many-body system.

scholarly journals Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Arik Bergman ◽  
Robert Duggan ◽  
Kavita Sharma ◽  
Moshe Tur ◽  
Avi Zadok ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Brillouin Scattering ◽  
Optical Gain ◽  
Single Mode ◽  
Exceptional Point ◽  
Small Scale ◽  
Time Symmetry ◽  
Topological Features ◽  
Gain And Loss ◽  
Exotic Physics

AbstractThe exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has recently drawn a great deal of attention. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. So far, these principles have been implemented at the expense of precise fabrication and tuning requirements, involving tailored nano-structured devices with controlled optical gain and loss. In this work, anti-parity-time symmetric phase transitions and exceptional point singularities are demonstrated in a single strand of single-mode telecommunication fibre, using a setup consisting of off-the-shelf components. Two propagating signals are amplified and coupled through stimulated Brillouin scattering, enabling exquisite control over the interaction-governing non-Hermitian parameters. Singular response to small-scale variations and topological features arising around the exceptional point are experimentally demonstrated with large precision, enabling robustly enhanced response to changes in Brillouin frequency shift.

scholarly journals Fine structures of valley-polarized excitonic states in monolayer transitional metal dichalcogenides

Nanophotonics ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1811-1829 ◽  
Author(s):  
Zhipeng Li ◽  
Tianmeng Wang ◽  
Shengnan Miao ◽  
Zhen Lian ◽  
Su-Fei Shi
Keyword(s):  
Optical Excitation ◽  
Coherence Time ◽  
Two Dimensions ◽  
Degree Of Freedom ◽  
Research Progress ◽  
Many Body ◽  
Transitional Metal ◽  
Metal Dichalcogenides ◽  
Fine Structures ◽  
Excitonic States

AbstractMonolayer transitional metal dichalcogenides (TMDCs), a new class of atomically thin semiconductor, respond to optical excitation strongly with robust excitons, which stem from the reduced screening in two dimensions. These excitons also possess a new quantum degree of freedom known as valley spin, which has inspired the field of valleytronics. The strongly enhanced Coulomb interaction allows the exciton to bind with other particles to form new excitonic states. However, despite the discovery of trions, most of the excitonic states in monolayer TMDCs remain elusive until recently, when new light was shed into the fascinating excitonic fine structures with drastically improved sample quality through boron nitride encapsulation. Here, we review the latest research progress on fine structures of excitonic states in monolayer TMDCs, with a focus on tungsten-based TMDCs and related alloy. Many of the new excitonic complexes inherit the valley degree of freedom, and the valley-polarized dark excitonic states are of particular interest because of their long lifetime and possible long valley coherence time. The capability of resolving the excitonic fine structures also enables the investigation of exciton–phonon interactions. The knowledge of the interlayer between excitons and other particles not only advances our understanding of many-body effects in the monolayer TMDCs but also provides guidance on future applications based on TMDCs.

Prediction of potential well structure formed in spherical inertial electrostatic confinement fusion devices with various parameters

2012 ◽  
Vol 79 (3) ◽  
pp. 295-303
Author(s):  
M. GHASEMI ◽  
M. HABIBI ◽  
R. AMROLLAHI
Keyword(s):  
Injection System ◽  
Potential Well ◽  
Inertial Electrostatic Confinement ◽  
Circulating Current ◽  
Ion Energies ◽  
Electrostatic Confinement ◽  
Confinement Fusion ◽  
Potential Structure ◽  
Radial Potential ◽  
Inertial Electrostatic Confinement Fusion

AbstractIn this paper, the theoretical analysis regarding potential structure on the inertial electrostatic confinement fusion devices has been carried out. Negatively biased grid as cathode placed at the center of the device surrounded by anode is assumed. The device is an ion-injection system and electrons may be emitted from the surface of the cathode. So the existence of both ion and electron currents inside the cathode is considered. Dependence of radial potential well structure on some important parameters as the spreads in the normalized total and angular electron and ion energies, the ratio of ion circulating current to electron circulating current, ion perveance, and grid transparency are investigated by solving Poisson equation.

scholarly journals Escape time from potential wells of strongly nonlinear oscillators with slowly varying parameters

2005 ◽  
Vol 2005 (3) ◽  
pp. 365-375 ◽  
Author(s):  
Jianping Cai ◽  
Y. P. Li ◽  
Xiaofeng Wu
Keyword(s):  
Elliptic Function ◽  
Nonlinear Oscillators ◽  
Oscillatory System ◽  
Escape Time ◽  
Potential Well ◽  
Jacobian Elliptic Function ◽  
Potential Wells ◽  
Varying Parameters ◽  
Strongly Nonlinear ◽  
Strongly Nonlinear Oscillators

The effect of negative damping to an oscillatory system is to force the amplitude to increase gradually and the motion will be out of the potential well of the oscillatory system eventually. In order to deduce the escape time from the potential well of quadratic or cubic nonlinear oscillator, the multiple scales method is firstly used to obtain the asymptotic solutions of strongly nonlinear oscillators with slowly varying parameters, and secondly the character of modulus of Jacobian elliptic function is applied to derive the equations governing the escape time. The approximate potential method, instead of Taylor series expansion, is used to approximate the potential of an oscillation system such that the asymptotic solution can be expressed in terms of Jacobian elliptic function. Numerical examples verify the efficiency of the present method.

The Escape of Particles from a Confining Potential well

1992 ◽  
Vol 290 ◽  
Author(s):  
James P. Lavine ◽  
Edmund K. Banghart ◽  
Joseph M. Pimbley
Keyword(s):  
Diffusion Coefficient ◽  
Chemical Reactions ◽  
Smoluchowski Equation ◽  
Escape Rate ◽  
Potential Well ◽  
Potential Wells ◽  
Confining Potential ◽  
Potential Shape ◽  
Well Depth ◽  
Electron Devices

AbstractMany electron devices and chemical reactions depend on the escape rate of particles confined by potential wells. When the diffusion coefficient of the particle is small, the carrier continuity or the Smoluchowski equation is used to study the escape rate. This equation includes diffusion and field-aided drift. In this work solutions to the Smoluchowski equation are probed to show how the escape rate depends on the potential well shape and well depth. It is found that the escape rate varies by up to two orders of magnitude when the potential shape differs for a fixed well depth.

scholarly journals Bonding xenon and krypton on the surface of uranium dioxide single crystal

Nukleonika ◽  
2014 ◽  
Vol 59 (3) ◽  
pp. 83-89
Author(s):  
Ludwik Dąbrowski ◽  
Marcin Szuta
Keyword(s):  
Single Crystal ◽  
Uranium Dioxide ◽  
Density Functional ◽  
Metallic Surface ◽  
Potential Well ◽  
Metallic Surfaces ◽  
Potential Wells ◽  
Cell Parameters ◽  
Super Cell ◽  
Calculation Results

Abstract We present density functional theory (DFT) calculation results of krypton and xenon atoms interaction on the surface of uranium dioxide single crystal. A pseudo-potential approach in the generalised gradient approximation (GGA) was applied using the ABINIT program package. To compute the unit cell parameters, the 25 atom super-cell was chosen. It has been revealed that close to the surface of a potential well is formed for xenon and krypton atom due to its interaction with the atoms of oxygen and uranium. Depth and shape of the well is the subject of ab initio calculations in adiabatic approximation. The calculations were performed both for the case of oxygenic and metallic surfaces. It has been shown that the potential well for the oxygenic surface is deeper than for the metallic surface. The thermal stability of immobilising the atoms of krypton and xenon in the potential wells were evaluated. The results are shown in graphs.

The Control of Stochastic Resonance by Harmonic Signal

2011 ◽  
Vol 50-51 ◽  
pp. 559-563 ◽  
Author(s):  
Mei Li Zhang ◽  
Min Lin
Keyword(s):  
Numerical Simulations ◽  
Stochastic Resonance ◽  
Harmonic Signal ◽  
New Method ◽  
Potential Wells ◽  
Bistable Systems ◽  
The Asymmetry ◽  
Resonance Control ◽  
Double Well Potential

The symmetry in a double-well potential of bistable systems subject to the action of a harmonic signal is broken. By variation of the amplitude of a harmonic signal, the asymmetry of bistable systems can be effectively controlled, the transitions probability between the two potential wells is increased and has influence on the effect of stochastic resonance in bistable systems. Numerical simulations show that adjusting the amplitude of a harmonic signal can produce stochastic resonance or make stochastic resonance more intense in bistable systems. It is a new method for stochastic resonance control.

scholarly journals Shells and the Potential Wells of Elliptical Galaxies

1987 ◽  
Vol 127 ◽  
pp. 249-259
Author(s):  
P.J. Quinn ◽  
Lars Hernquist
Keyword(s):  
Dark Matter ◽  
Large Range ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Potential Well ◽  
Potential Wells ◽  
Shell System ◽  
History Of

A survey of the possible variety of sharp-edged, caustic features that may arise in the collision of galaxies with very different masses and sizes (Hernquist and Quinn 1986a) has shown that in general shells are morphologically very complex. It is therefore not easy to determine the history of the collision that produced the shells nor the properties of the galaxies involved. However, a small number of shell galaxies (notably NGC 3923) have a sufficiently simple and orderly shell distribution that we believe the shells were formed by a chance very symmetric and simple encounter. In such cases we are presented with a unique opportunity to investigate the potential well of an elliptical galaxy over a large range in radius (≃ 0.5re − 20re). An analysis of the NGC 3923 shell system (Hernquist and Quinn 1986b) has shown that a large amount of dark matter is present (Mdark≃ 40Mluminous, r < 17re).

scholarly journals Exceptional dynamical quantum phase transitions in periodically driven systems

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ryusuke Hamazaki
Keyword(s):  
Free Energy ◽  
Phase Transitions ◽  
Fundamental Problem ◽  
Quantum Phase Transitions ◽  
Quantum Phase ◽  
Exceptional Point ◽  
Many Body ◽  
Periodically Driven ◽  
Time Regime ◽  
Short Time

AbstractExtending notions of phase transitions to nonequilibrium realm is a fundamental problem for statistical mechanics. While it was discovered that critical transitions occur even for transient states before relaxation as the singularity of a dynamical version of free energy, their nature is yet to be elusive. Here, we show that spontaneous symmetry breaking can occur at a short-time regime and causes universal dynamical quantum phase transitions in periodically driven unitary dynamics. Unlike conventional phase transitions, the relevant symmetry is antiunitary: its breaking is accompanied by a many-body exceptional point of a nonunitary operator obtained by space-time duality. Using a stroboscopic Ising model, we demonstrate the existence of distinct phases and unconventional singularity of dynamical free energy, whose signature can be accessed through quasilocal operators. Our results open up research for hitherto unknown phases in short-time regimes, where time serves as another pivotal parameter, with their hidden connection to nonunitary physics.

scholarly journals Many-body quantum metrology with scalar bosons in a single potential well

2019 ◽  
Vol 99 (4) ◽  
Author(s):  
Julien M. E. Fraïsse ◽  
Jae-Gyun Baak ◽  
Uwe R. Fischer
Keyword(s):  
Potential Well ◽  
Quantum Metrology ◽  
Many Body ◽  
Single Potential
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