Showing 1–20 of 20 results for author: Ge, R

MEDA: Measurement-Efficient Disorder-Aware Majorana Zero Mode Detection in Realistic Devices

Authors: Nathan Jones, Binayyak Roy, Valentine Mohaugen, Ian Lewis, Toby Cox, Sumanta Tewari, Rong Ge

Abstract: Fault-tolerant topological quantum computing relies on identifying Majorana zero modes (MZMs), but reliable detection in realistic devices remains challenging. Conventional topological indicators are inherently biased in finite, disordered systems, blurring the distinction between true MZMs and trivial states. Furthermore, attempts to map these indicators to real observables via machine learning r… ▽ More Fault-tolerant topological quantum computing relies on identifying Majorana zero modes (MZMs), but reliable detection in realistic devices remains challenging. Conventional topological indicators are inherently biased in finite, disordered systems, blurring the distinction between true MZMs and trivial states. Furthermore, attempts to map these indicators to real observables via machine learning require dense, expensive conductance measurements, creating a severe scaling bottleneck. To simultaneously address topological bias and measurement limitations, we present MEDA: a Measurement-Efficient, Disorder-Aware framework for MZM detection in realistic devices. MEDA maps sparse, practically obtainable observables directly to the robust periodic disorder invariant (PDI). Using a novel sparse parameter regime, MEDA reduces measurement volume by 10x while maintaining predictive quality, even in moderate to strong disorder regimes that limit conventional methods. Furthermore, MEDA naturally prioritizes input features consistent with the topological gap protocol, demonstrating strong physical interpretability. △ Less

Submitted 16 August, 2026; v1 submitted 28 July, 2026; originally announced July 2026.

Comments: Accepted to 2026 IEEE International Conference on Quantum Computing and Engineering

Cavity induced many-body localization

Authors: Rong-Chun Ge, Saeed Rahmanian Koshkaki, Michael H. Kolodrubetz

Abstract: In this manuscript, we explore the feasibility of achieving many-body localization in the context of cavity quantum electrodynamics at strong coupling. Working with a spinless electronic Hubbard chain sitting coupled to a single-mode cavity, we show that the global coupling between electrons and photons -- which generally would be expected to delocalize the fermionic excitations -- can instead fav… ▽ More In this manuscript, we explore the feasibility of achieving many-body localization in the context of cavity quantum electrodynamics at strong coupling. Working with a spinless electronic Hubbard chain sitting coupled to a single-mode cavity, we show that the global coupling between electrons and photons -- which generally would be expected to delocalize the fermionic excitations -- can instead favor the appearance of localization. This is supported by a novel high-frequency expansion that correctly accounts for electron-photon interaction at strong coupling, as well as numerical calculations in both single particle and many-bod regimes. We find evidence that many-body localization may survive strong quantum fluctuations of the photon number by exploring energy dependence, seeing signatures of localization down to photon numbers as small as $n\sim2$. △ Less

Submitted 19 July, 2023; v1 submitted 14 August, 2022; originally announced August 2022.

Comments: Updated version with more details provided

Universal Non-Volatile Resistive Switching Behavior in 2D Metal Dichalcogenides Featuring Unique Conductive-Point Random Access Memory Effect

Authors: Xiaohan Wu, Ruijing Ge, Yuqian Gu, Emmanuel Okogbue, Jianping Shi, Abhay Shivayogimath, Peter Bøggild, Timothy J. Booth, Yanfeng Zhang, Yeonwoong Jung, Jack C. Lee, Deji Akinwande

Abstract: Two-dimensional materials have been discovered to exhibit non-volatile resistive switching (NVRS) phenomenon. In our work, we reported the universal NVRS behavior in a dozen metal dichalcogenides, featuring low switching voltage, large on/off ratio, fast switching speed and forming free characteristics. A unique conductive-point random access memory (CPRAM) effect is used to explain the switching… ▽ More Two-dimensional materials have been discovered to exhibit non-volatile resistive switching (NVRS) phenomenon. In our work, we reported the universal NVRS behavior in a dozen metal dichalcogenides, featuring low switching voltage, large on/off ratio, fast switching speed and forming free characteristics. A unique conductive-point random access memory (CPRAM) effect is used to explain the switching mechanisms, supported by experimental results from current-sweep measurements. △ Less

Submitted 7 October, 2021; originally announced October 2021.

Comments: 3 pages, 5 figures, IEEE conference(2021 5th EDTM)

Journal ref: 2021 5th IEEE Electron Devices Technology & Manufacturing Conference (EDTM), pp. 1-3. IEEE, 2021

Floquet engineering of lattice structure and dimensionality in twisted moiré heterobilayers

Authors: Rong-Chun Ge, Michael Kolodrubetz

Abstract: We present an experimental proposal to tune the effective lattice structure in twisted transition metal dichalcogenide (TMD) heterobilayers with time-periodic Floquet drive. We show that elliptically polarized light with sub-terahertz frequencies $\hbarω\sim 1$ meV and moderate electric fields $E\sim0.2$~MV/cm allows tuning between the native triangular lattice and a square lattice, while linearly… ▽ More We present an experimental proposal to tune the effective lattice structure in twisted transition metal dichalcogenide (TMD) heterobilayers with time-periodic Floquet drive. We show that elliptically polarized light with sub-terahertz frequencies $\hbarω\sim 1$ meV and moderate electric fields $E\sim0.2$~MV/cm allows tuning between the native triangular lattice and a square lattice, while linearly polarized light enables dimensional reduction to a quasi-one-dimensional geometry. Without drive, these twisted TMDs simulate the single band Fermi-Hubbard model; we show that this approximation still holds in the presence of drive. This control opens the door to explore a rich variety of correlated phases of matter, such as spin liquids and d-wave superconductivity. △ Less

Submitted 23 July, 2021; v1 submitted 17 March, 2021; originally announced March 2021.

Comments: 7 pages, 6 figures

Quasiperiodic Floquet-Thouless energy pump

Authors: Frederik Nathan, Rongchun Ge, Snir Gazit, Mark S. Rudner, Michael Kolodrubetz

Abstract: Recent work [M. H. Kolodrubetz et al, PRL 120, 150601] has demonstrated that periodically driven one-dimensional fermionic systems can support quantized energy pumping resulting from an adiabatic modulation of a second parameter. In this work, we explore this topological Floquet-Thouless energy pump in the quasiperiodic driving regime where the parametric driving occurs at finite frequency. We sho… ▽ More Recent work [M. H. Kolodrubetz et al, PRL 120, 150601] has demonstrated that periodically driven one-dimensional fermionic systems can support quantized energy pumping resulting from an adiabatic modulation of a second parameter. In this work, we explore this topological Floquet-Thouless energy pump in the quasiperiodic driving regime where the parametric driving occurs at finite frequency. We show that quantization of energy pumping persists for finite ramping frequencies, as long as they are incommensurate with the driving frequency, and the system remains localized by spatial disorder. Thus, the topological Floquet-Thouless energy pump is stable beyond the adiabatic regime, occupying a finite region of parameter space. Phase transitions away from these topological phases are accompanied by delocalization in position space, photon number (energy) space, or both. Using a dimensional reduction scheme, we demonstrate that a related phase can be realized with a cavity-qubit system driven by two incommensurate modes. △ Less

Submitted 18 October, 2021; v1 submitted 22 October, 2020; originally announced October 2020.

Report number: QDEV CMT NBI 2020

Journal ref: Phys. Rev. Lett. 127, 166804 (2021)

Floquet engineering flat bands for bosonic fractional quantum Hall in small lattices

Authors: Rongchun Ge, Michael Kolodrubetz

Abstract: The quest to realize novel phases of matter with topological order is an important pursuit with implications for strongly correlated physics and quantum information. Utilizing ideas from state-of-the-art coherent control of artificial quantum systems such as superconducting circuits, we present a proposal to realize bosonic fractional quantum Hall physics on small lattices by creating nearly flat… ▽ More The quest to realize novel phases of matter with topological order is an important pursuit with implications for strongly correlated physics and quantum information. Utilizing ideas from state-of-the-art coherent control of artificial quantum systems such as superconducting circuits, we present a proposal to realize bosonic fractional quantum Hall physics on small lattices by creating nearly flat topological bands using staggered flux patterns. Fingerprints of fractionalization through charge pumping can be observed with nearly perfect quantization using as few as 24 lattice sites (two photons). We suggest an implementation using a finite lattice of superconducting qubits with cylindrical connectivity on both triangular and square lattices. △ Less

Submitted 23 July, 2021; v1 submitted 31 August, 2020; originally announced September 2020.

Comments: 4 figures (updated)

Journal ref: Phys. Rev. B 104, 035427 (2021)

Single-defect Memristor in MoS$_2$ Atomic-layer

Authors: Saban M. Hus, Ruijing Ge, Po-An Chen, Meng-Hsueh Chiang, Gavin E. Donnelly, Wonhee Ko, Fumin Huang, Liangbo Liang, An-Ping Li, Deji Akinwande

Abstract: Non-volatile resistive switching, also known as memristor effect in two terminal devices, has emerged as one of the most important components in the ongoing development of high-density information storage, brain-inspired computing, and reconfigurable systems. Recently, the unexpected discovery of memristor effect in atomic monolayers of transitional metal dichalcogenide sandwich structures has add… ▽ More Non-volatile resistive switching, also known as memristor effect in two terminal devices, has emerged as one of the most important components in the ongoing development of high-density information storage, brain-inspired computing, and reconfigurable systems. Recently, the unexpected discovery of memristor effect in atomic monolayers of transitional metal dichalcogenide sandwich structures has added a new dimension of interest owing to the prospects of size scaling and the associated benefits. However, the origin of the switching mechanism in atomic sheets remains uncertain. Here, using monolayer MoS$_2$ as a model system, atomistic imaging and spectroscopy reveal that metal substitution into sulfur vacancy results in a non-volatile change in resistance. The experimental observations are corroborated by computational studies of defect structures and electronic states. These remarkable findings provide an atomistic understanding on the non-volatile switching mechanism and open a new direction in precision defect engineering, down to a single defect, for achieving optimum performance metrics including memory density, switching energy, speed, and reliability using atomic nanomaterials. △ Less

Submitted 4 February, 2020; originally announced February 2020.

Anti-chiral edge states in an exciton polariton strip

Authors: S. Mandal, R. Ge, T. C. H. Liew

Abstract: We present a scheme to obtain anti-chiral edge states in an exciton-polariton honeycomb lattice with strip geometry, where the modes corresponding to both edges propagate in the same direction. Under resonant pumping the effect of a polariton condensate with nonzero velocity in one linear polarization is predicted to tilt the dispersion of polaritons in the other, which results in an energy shift… ▽ More We present a scheme to obtain anti-chiral edge states in an exciton-polariton honeycomb lattice with strip geometry, where the modes corresponding to both edges propagate in the same direction. Under resonant pumping the effect of a polariton condensate with nonzero velocity in one linear polarization is predicted to tilt the dispersion of polaritons in the other, which results in an energy shift between two Dirac cones and the otherwise flat edge states become tilted. Our simulations show that due to the spatial separation from the bulk modes the edge modes are robust against disorder. △ Less

Submitted 18 March, 2019; originally announced March 2019.

Comments: 6 pages, 5 figures

Journal ref: Phys. Rev. B 99, 115423 (2019)

Exciton-polariton topological insulator

Authors: S. Klembt, T. H. Harder, O. A. Egorov, K. Winkler, R. Ge, M. A. Bandres, M. Emmerling, L. Worschech, T. C. H. Liew, M. Segev, C. Schneider, S. Höfling

Abstract: Topological insulators (TIs) are a striking example of materials in which topological invariants are manifested in robustness against perturbations. Their most prominent feature is the emergence of topological edge states with reduced dimension at the boundary between areas with distinct topological invariants. The observable physical effect is unidirectional robust transport, unaffected by defect… ▽ More Topological insulators (TIs) are a striking example of materials in which topological invariants are manifested in robustness against perturbations. Their most prominent feature is the emergence of topological edge states with reduced dimension at the boundary between areas with distinct topological invariants. The observable physical effect is unidirectional robust transport, unaffected by defects or disorder. TIs were originally observed in the integer quantum Hall effect for fermionic systems of correlated electrons. However, during the past decade the concepts of topological physics have been introduced into numerous fields beyond condensed matter, ranging from microwaves and photonic systems to cold atoms, acoustics and even mechanics. Recently, TIs were proposed in exciton-polariton systems organized as honeycomb lattices, under the influence of a magnetic field. Topological phenomena in polaritons are fundamentally different from all topological effects demonstrated experimentally thus far: exciton-polaritons are part-light part-matter quasiparticles emerging from the strong coupling of quantum well excitons and cavity photons. Here, we demonstrate experimentally the first exciton-polariton TI. This constitutes the first symbiotic light-matter TIs. Our polariton lattice is excited non-resonantly, and the chiral topological polariton edge mode is populated by a polariton condensation mechanism. We image real- and Fourier-space to measure photoluminescence, and demonstrate that the topological edge mode avoids defects, and that the propagation direction of the mode can be reversed by inverting the applied magnetic field. Our exciton-polariton TI paves the way for a variety of new topological phenomena, as they involve light-matter interaction, gain, and perhaps most importantly - exciton-polaritons interact with one another as a nonlinear many-body system. △ Less

Submitted 9 August, 2018; originally announced August 2018.

Journal ref: Nature 562, 552-556 (2018)

Floquet Topological Polaritons in Semiconductor Microcavities

Authors: Rongchun Ge, Wijnand Broer, Timothy C. H. Liew

Abstract: We propose and model Floquet topological polaritons in semiconductor microcavities, using the interference of frequency detuned coherent fields to provide a time periodic potential. For arbitrarily weak field strength, where the Floquet frequency is larger than the relevant bandwidth of the system, a Chern insulator is obtained. As the field strength is increased, a topological phase transition is… ▽ More We propose and model Floquet topological polaritons in semiconductor microcavities, using the interference of frequency detuned coherent fields to provide a time periodic potential. For arbitrarily weak field strength, where the Floquet frequency is larger than the relevant bandwidth of the system, a Chern insulator is obtained. As the field strength is increased, a topological phase transition is observed with an unpaired Dirac cone proclaiming the anomalous Floquet topological insulator. As the relevant bandwidth increases even further, an exotic Chern insulator with flat band is observed with unpaired Dirac cone at the second critical point. Considering the polariton spin degree of freedom, we find that the choice of field polarization allows oppositely polarized polaritons to either co-propagate or counter-propagate in chiral edge states. △ Less

Submitted 2 May, 2018; originally announced May 2018.

Comments: Accepted by PRB

Journal ref: PhysRevB.97.195305 2018

Towards Universal Non-Volatile Resistance Switching in Non-metallic Monolayer Atomic Sheets

Authors: Ruijing Ge, Xiaohan Wu, Myungsoo Kim, Harry Chou, Sushant Sonde, Li Tao, Jack C. Lee, Deji Akinwande

Abstract: Here, we report the intriguing observation of stable non-volatile resistance switching (NVRS) in single-layer atomic sheets sandwiched between metal electrodes. NVRS is observed in the prototypical semiconducting (MX2, M=Mo, W; and X=S, Se) transitional metal dichalcogenides (TMDs), and insulating hexagonal boron nitride (h-BN), which alludes to the universality of this phenomenon in non-metallic… ▽ More Here, we report the intriguing observation of stable non-volatile resistance switching (NVRS) in single-layer atomic sheets sandwiched between metal electrodes. NVRS is observed in the prototypical semiconducting (MX2, M=Mo, W; and X=S, Se) transitional metal dichalcogenides (TMDs), and insulating hexagonal boron nitride (h-BN), which alludes to the universality of this phenomenon in non-metallic 2D monolayers, and features forming-free switching. This observation of NVRS phenomenon, widely attributed to ionic diffusion, filament and interfacial redox in bulk oxides and electrolytes, inspires new studies on defects, ion transport and energetics at the sharp interfaces between atomically-thin sheets and conducting electrodes. From a contemporary perspective, switching is all the more unexpected in monolayers since leakage current is a fundamental limit in ultra-thin oxides. Emerging device concepts in non-volatile flexible memory fabrics, and brain-inspired (neuromorphic) computing could benefit substantially from the pervasive NVRS effect and the associated wide materials and engineering co-design opportunity. Experimentally, a 50 GHz radio-frequency (RF) monolayer switch is demonstrated, which opens up a new application for electronic zero-static power RF switching technology. △ Less

Submitted 13 September, 2017; originally announced September 2017.

Reply to "Comment on "Normalization of quasinormal modes in leaky optical cavities and plasmonic resonators" " by E. A. Muljarov and W. Langbein

Authors: Philip Trøst Kristensen, Rong-Chun Ge, Stephen Hughes

Abstract: We refute all claims of the "Comment on "Normalization of quasinormal modes in leaky optical cavities and plasmonic resonators" " by E. A. Muljarov and W. Langbein (arXiv:1602.07278v1). Based entirely on information already contained in our original article (P. T. Kristensen, R.-C. Ge and S. Hughes, Physical Review A 92, 053810 (2015)), we dismiss every point of criticism as being completely unjus… ▽ More We refute all claims of the "Comment on "Normalization of quasinormal modes in leaky optical cavities and plasmonic resonators" " by E. A. Muljarov and W. Langbein (arXiv:1602.07278v1). Based entirely on information already contained in our original article (P. T. Kristensen, R.-C. Ge and S. Hughes, Physical Review A 92, 053810 (2015)), we dismiss every point of criticism as being completely unjustified and point out how important parts of our argumentation appear to have been overlooked by the Comment Authors. In addition, we provide additional calculations showing directly the link between the normalizations by Sauvan et al. and Muljarov et al., which were not included in our original article. △ Less

Submitted 16 May, 2016; originally announced May 2016.

Journal ref: Phys. Rev. A 96, 017802 (2017)

Quasinormal mode theory and modelling of electron energy loss spectroscopy for plasmonic nanostructures

Authors: Rong-Chun Ge, Stephen Hughes

Abstract: Understanding light-matter interactions using localized surface plasmons (LSPs) is of fundamental interest in classical and quantum plasmonics and has a wide range of applications. In order to understand the spatial properties of LSPs, electron energy loss spectroscopy (EELS) is a common and powerful method of spatially resolving the extreme localized fields that can be obtained with metal resonat… ▽ More Understanding light-matter interactions using localized surface plasmons (LSPs) is of fundamental interest in classical and quantum plasmonics and has a wide range of applications. In order to understand the spatial properties of LSPs, electron energy loss spectroscopy (EELS) is a common and powerful method of spatially resolving the extreme localized fields that can be obtained with metal resonators. However, modelling EELS for general shaped resonators presents a major challenge in computational electrodynamics, requiring the full photon Green function as a function of two space points and frequency. Here we present an intuitive and computationally simple method for computing EELS maps of plasmonic resonators using a quasinormal mode (QNM) expansion technique. By separating the contribution of the QNM and the bulk material, we give closed-form analytical formulas for the plasmonic QNM contribution to the EELS maps. We exemplify our technique for a split ring resonator, a gold nanorod, and a nanorod dimer structure. The method is accurate, intuitive, and gives orders of magnitude improvements over direct dipole simulations that numerically solve the full 3D Maxwell equations. We also show how the same QNM Green function can be used to obtain the Purcell factor (and projected local density of optical states) from quantum dipole emitters or two level atoms, and we demonstrate how the spectral features differ in general to the EELS spectrum. △ Less

Submitted 19 March, 2016; v1 submitted 5 October, 2015; originally announced October 2015.

Comments: 9 pages, 4 figures

Journal ref: J. Opt. 18, 054002 (2016)

Quantum dynamics of two quantum dots coupled through localized plasmons: An intuitive and accurate quantum optics approach using quasinormal modes

Authors: Rong-Chun Ge, Stephen Hughes

Abstract: We study the quantum dynamics of two quantum dots (QDs) or artificial atoms coupled through the fundamental localized plasmon of a gold nanorod resonator. We derive an intuitive and efficient time-local master equation, in which the effect of the metal nanorod is taken into consideration self-consistently using a quasinormal mode (QNM) expansion technique of the photon Green function. Our efficien… ▽ More We study the quantum dynamics of two quantum dots (QDs) or artificial atoms coupled through the fundamental localized plasmon of a gold nanorod resonator. We derive an intuitive and efficient time-local master equation, in which the effect of the metal nanorod is taken into consideration self-consistently using a quasinormal mode (QNM) expansion technique of the photon Green function. Our efficient QNM technique offers an alternative and more powerful approach over the standard Jaynes-Cummings model, where the radiative decay, nonradiative decay, and spectral reshaping effect of the electromagnetic environment is rigorously included in a clear and transparent way. We also show how one can use our approach to compliment the approximate Jaynes-Cummings model in certain spatial regimes where it is deemed to be valid. We then present a study of the quantum dynamics and photoluminescence spectra of the two plasmon-coupled QDs. We first explore the non-Markovian regime, which is found to be important only on the ultrashort time scale of the plasmon mode which is about 40$\,$fs. For the field free evolution case of excited QDs near the nanorod, we demonstrate how spatially separated QDs can be effectively coupled through the plasmon resonance and we show how frequencies away from the plasmon resonance can be more effective for coherently coupling the QDs. Despite the strong inherent dissipation of gold nanoresonators, we show that qubit entanglements as large as 0.7 can be achieved from an initially separate state, which has been limited to less than 0.5 in previous work for weakly coupled reservoirs. We also study the superradiance and subradiance decay dynamics of the QD pair. Finally, we investigate the rich quantum dynamics of QDs that are incoherently pumped, ... △ Less

Submitted 17 November, 2015; v1 submitted 8 May, 2015; originally announced May 2015.

Journal ref: Phys. Rev. B 92, 205420 (2015)

Design of an efficient single photon source from a metallic nanorod dimer: a quasinormal mode finite-difference time-domain approach

Authors: Rong-Chun Ge, S. Hughes

Abstract: We describe how the finite-difference time-domain (FDTD) technique can be used to compute the quasinormal mode (QNM) for metallic nano-resonators, which is important for describing and understanding light-matter interactions in nanoplasmonics. We use the QNM to model the enhanced spontaneous emission rate for dipole emitters near a gold nanorod dimer structure using a newly developed QNM expansion… ▽ More We describe how the finite-difference time-domain (FDTD) technique can be used to compute the quasinormal mode (QNM) for metallic nano-resonators, which is important for describing and understanding light-matter interactions in nanoplasmonics. We use the QNM to model the enhanced spontaneous emission rate for dipole emitters near a gold nanorod dimer structure using a newly developed QNM expansion technique. Significant enhanced photon emission factors of around 1500 are obtained with large output $β$-factors of about $60\%$. △ Less

Submitted 23 January, 2015; originally announced January 2015.

Journal ref: Optics Letters, Vol. 39, Issue 14, pp. 4235-4238 (2014)

Quasi-normal mode approach to the local-field problem in quantum optics

Authors: Rong-Chun Ge, Jeff F. Young, S. Hughes

Abstract: The local-field (LF) problem of a finite-size dipole emit- ter radiating inside a lossy inhomogeneous structure is a long-standing and challenging quantum optical problem, and it now is becoming more important due to rapid advances in solid-state fabrication technologies. Here we introduce a simple and accurate quasi-normal mode (QNM) technique to solve this problem analyti- cally by separating th… ▽ More The local-field (LF) problem of a finite-size dipole emit- ter radiating inside a lossy inhomogeneous structure is a long-standing and challenging quantum optical problem, and it now is becoming more important due to rapid advances in solid-state fabrication technologies. Here we introduce a simple and accurate quasi-normal mode (QNM) technique to solve this problem analyti- cally by separating the scattering problem into contribu- tions from the QNM and an image dipole. Using a real- cavity model to describe an artificial atom inside a lossy and dispersive gold nanorod, we show when the contri- bution of the QNM to LFs will dominate over the homo- geneous contribution. We also show how to accurately describe surface scattering for real cavities that are close to the metal interface and explore regimes when the surface scattering dominates. Our results offer an intui- tive picture of the underlying physics for the LF problem and facilitate the understanding of novel photon sources within lossy structures. △ Less

Submitted 13 April, 2015; v1 submitted 23 January, 2015; originally announced January 2015.

Journal ref: Optica, Vol. 2, Issue 3, pp. 246-249 (2015)

Quasinormal mode approach to modelling light-emission and propagation in nanoplasmonics

Authors: Rong-Chun Ge, Philip Trost Kristensen, Jeff. F. Young, Stephen Hughes

Abstract: We describe a powerful and intuitive technique for modeling light-matter interactions in classical and quantum nanoplasmonics. Our approach uses a quasinormal mode expansion of the Green function within a metal nanoresonator of arbitrary shape, together with a Dyson equation, to derive an expression for the spontaneous decay rate and far field propagator from dipole oscillators outside resonators.… ▽ More We describe a powerful and intuitive technique for modeling light-matter interactions in classical and quantum nanoplasmonics. Our approach uses a quasinormal mode expansion of the Green function within a metal nanoresonator of arbitrary shape, together with a Dyson equation, to derive an expression for the spontaneous decay rate and far field propagator from dipole oscillators outside resonators. For a single quasinormal mode, at field positions outside the quasi-static coupling regime, we give a closed form solution for the Purcell factor and generalized effective mode volume. We augment this with an analytic expression for the divergent LDOS very near the metal surface, which allows us to derive a simple and highly accurate expression for the electric field outside the metal resonator at distances from a few nanometers to infinity. This intuitive formalism provides an enormous simplification over full numerical calculations and fixes several pending problems in quasinormal mode theory. △ Less

Submitted 2 June, 2014; v1 submitted 10 December, 2013; originally announced December 2013.

Accessing quantum nanoplasmonics in a hybrid quantum-dot metal nanosystem: Mollow triplet of a quantum dot near a metal nanoparticle

Authors: Rong-Chun Ge, C. Van Vlack, P. Yao, Jeff. F. Young, S. Hughes

Abstract: We present a theoretical study of the resonance fluorescence spectra of an optically driven quantum dot placed near a single metal nanoparticle. The metallic reservoir coupling is calculated for an 8-nm metal nanoparticle using a time-convolutionless master equation approach where the exact photon reservoir function is included using Green function theory. By exciting the system coherently near th… ▽ More We present a theoretical study of the resonance fluorescence spectra of an optically driven quantum dot placed near a single metal nanoparticle. The metallic reservoir coupling is calculated for an 8-nm metal nanoparticle using a time-convolutionless master equation approach where the exact photon reservoir function is included using Green function theory. By exciting the system coherently near the nanoparticle dipole mode, we show that the driven Mollow spectrum becomes highly asymmetric due to internal coupling effects with higher-order plasmons. We also highlight regimes of resonance squeezing and broadening as well as spectral reshaping through light propagation. Our master equation technique can be applied to any arbitrary material system, including lossy inhomogeneous structures, where mode expansion techniques are known to break down. △ Less

Submitted 22 April, 2013; originally announced April 2013.

Journal ref: Phys. Rev. B 87, 205425 (2013)

Mollow "quintuplets" from coherently-excited quantum dots

Authors: Rong-Chun Ge, S. Weiler, A. Ulhaq, S. M. Ulrich, M. Jetter, P. Michler, S. Hughes

Abstract: Charge-neutral excitons in semiconductor quantum dots have a small finite energy separation caused by the anisotropic exchange splitting. Coherent excitation of neutral excitons will generally excite both exciton components, unless the excitation is parallel to one of the dipole axes. We present a polaron master equation model to describe two-exciton pumping using a coherent continuous wave pump f… ▽ More Charge-neutral excitons in semiconductor quantum dots have a small finite energy separation caused by the anisotropic exchange splitting. Coherent excitation of neutral excitons will generally excite both exciton components, unless the excitation is parallel to one of the dipole axes. We present a polaron master equation model to describe two-exciton pumping using a coherent continuous wave pump field in the presence of a realistic anisotropic exchange splitting. We predict a five-peak incoherent spectrum, thus generalizing the Mollow triplet to become a Mollow quintuplet. We experimentally confirm such spectral quintuplets for In(Ga)As quantum dots and obtain very good agreement with theory. △ Less

Submitted 14 February, 2013; originally announced February 2013.

Journal ref: Optics Letters, Vol. 38, Issue 10, pp. 1691-1693 (2013)

Efficient Quantum Ratchet

Authors: Chuan-Feng Li, Rong-Chun Ge, Guang-Can Guo

Abstract: Quantum resonance is one of the main characteristics of the quantum kicked rotor, which has been used to induce accelerated ratchet current of the particles with a generalized asymmetry potential. Here we show that by desynchronizing the kicked potentials of the flashing ratchet [Phys. Rev. Lett. 94, 110603 (2005)], new quantum resonances are stimulated to conduct directed currents more efficientl… ▽ More Quantum resonance is one of the main characteristics of the quantum kicked rotor, which has been used to induce accelerated ratchet current of the particles with a generalized asymmetry potential. Here we show that by desynchronizing the kicked potentials of the flashing ratchet [Phys. Rev. Lett. 94, 110603 (2005)], new quantum resonances are stimulated to conduct directed currents more efficiently. Most distinctly, the missed resonances $κ=1.0π$ and $κ=3.0π$ are created out to induce even larger currents. At the same time, with the help of semiclassical analysis, we prove that our result is exact rather than phenomenon induced by errors of the numerical simulation. Our discovery may be used to realize directed transport efficiently, and may also lead to a deeper understanding of symmetry breaking for the dynamical evolution. △ Less

Submitted 16 June, 2012; originally announced June 2012.

Comments: 10 pages, 4 figures. Comments welcome