A model of semiconductor quantum dots coupled to phonons and laser light, which is relevant in the limit strong electronic confinement, investigated. For an arbitrary sequence excitations by ultrafast pulses, analytical solutions are obtained for all pertinent density-matrix elements. The results nonperturbative with respect coupling both light. derivation depends neither on a particular choice wave functions nor wave-vector dependence phonon interaction or dispersion. All components density...

We have analyzed the initial decoherence of strongly confined semiconductor quantum dots by performing four-wave-mixing experiments and comparing with theory. The measurements are in quantitative agreement analytical results accounting for pure dephasing induced acoustic phonons. confirm recent prediction an unusual nonmonotonous temperature dependence time.

The dynamics of strongly confined laser driven semiconductor quantum dots coupled to phonons is studied theoretically by calculating the time evolution reduced density matrix using a numerical path integral method. We explore cases long pulses, strong dot-phonon and dot-laser coupling, high temperatures, which, up now, have been inaccessible. find that phonon-induced damping Rabi rotations nonmonotonic function field increasing at low fields decreasing fields. This results in reappearance...

Recent observation of unusual vortex patterns in MgB(2) single crystals raised speculations about possible "type-1.5" superconductivity two-band materials, mixing the properties both type-I and type-II superconductors. However, strict application standard Ginzburg-Landau (GL) theory results simply proportional order parameters two bands-and does not support behavior. Here we derive extended GL formalism (accounting all terms next over small τ=1-T/T(c) parameter) for a clean s-wave...

Based on a representation of the functional integral as time evolution augmented density matrix we have worked out an implementation real-time path approach that is applicable to dynamics quantum dissipative systems with superohmic coupling environment. As prototype for such system consider laser-driven strongly confined semiconductor dot coupled acoustic phonons. First applications this already been published. Here, provide detailed description implementation, including discussion numerical...

A procedure to derive the Ginzburg-Landau (GL) theory from multiband BCS Hamiltonian is developed in a general case with an arbitrary number of bands and interaction matrix. It combines standard Gor'kov truncation subsequent reconstruction order match accuracies obtained terms. This recovers phenomenological GL as Landau model phase transitions but offers explicit microscopic expressions for relevant parameters. Detailed calculations are presented three-band system treated prototype...

The swing up of quantum emitter population (SUPER) scheme, taking a radically different off-resonant approach to coherently excite two-level system, is explained and proposed for single-photon generation from dots.

We study the long-time dynamics and stationary nonequilibrium state of an optically driven quantum dot coupled to acoustic phonons using numerically exact real-time path integrals a fourth-order correlation expansion. By exploring wide ranges temperatures, carrier-phonon carrier-light coupling strengths, we characterize compare solution known, approximatively derived results. It is found that analytical calculations tend overestimate influence coupling, particularly at low temperatures in...

A combination of strong Cooper pairing and weak superconducting fluctuations is crucial to achieve stabilize high-Tc superconductivity. We demonstrate that a coexistence shallow carrier band with deep pairing, together the Josephson-like pair transfer between bands couple two condensates, realizes an optimal multicomponent superconductivity regime: it preserves generate large gaps very high critical temperature but screens detrimental fluctuations, thereby suppressing pseudogap state....

We demonstrate theoretically that the single-photon purity of photons emitted from a quantum dot exciton prepared by phonon-assisted off-resonant excitation can be significantly higher in wide range parameters than obtained resonant preparation for otherwise identical conditions. Despite excitation, brightness stays on high level. These surprising findings exploit fact is two-step process where phonons first lead to relaxation between laser-dressed states while occupations are reached only...

In the nearest vicinity of critical temperature, types I and II conventional single-band superconductors interchange at Ginzburg-Landau parameter $\ensuremath{\kappa}=1/\sqrt{2}$. At lower temperatures this point unfolds into a narrow but finite interval $\ensuremath{\kappa}$'s, shaping an intertype (transitional) domain in $(\ensuremath{\kappa},T)$ plane. present work, based on extended formalism, we show that same picture two standard with transitional between applies also to multiband...

Abstract Ordinary superconductors are widely assumed insensitive to small concentrations of random nonmagnetic impurities, whereas strong disorder suppresses superconductivity and even makes superconductor-insulator transition occur. In between these limiting cases, a most fascinating regime can take place where enhances superconductivity. Hitherto, almost all theoretical studies have been conducted under the assumption that is completely independent random. real materials, however,...

Entangled photon pairs are key to many novel applications in quantum technologies. Semiconductor dots can be used as sources of on-demand, highly entangled photons. The fidelity a fixed maximally state is limited by the excitonic fine-structure splitting. This work demonstrates that, even if this splitting absent, degree entanglement cannot reach unity when excitation pulse two-photon resonance scheme has finite duration. degradation its origin dynamically induced exciton states caused laser...

The nonlinear optical response to ultrafast laser pulses of semiconductor quantum dots coupled acoustic phonons is discussed on the basis closed-form analytical results valid for in strong confinement regime. General properties four-wave-mixing (FWM) signals are derived from formulas. Numerical presented two-pulse FWM single and dot ensembles time frequency domains. Interestingly, initial decay signal found depend nonmonotonously temperature delay time. In general, phonon coupling leads a...

The thermodynamic stability of a trapped Bose gas with two-component condensate, e.g., atoms in two distinct hyperfine states or binary gaseous mixture, is considered on the basis modified Gross-Pitaevskii equations. Under certain conditions system becomes unstable respect to stratification, i.e., spatial separation between condensates. One condensate assumes donutlike distribution, while other retains centered distribution. Possible applications theory recent experimental data overlapping...

We derive the extended Ginzburg-Landau (GL) formalism for a clean $s$-wave two-band superconductor by employing systematic expansion of free-energy functional and corresponding matrix gap equation in powers small deviation from critical temperature $\ensuremath{\tau}=1\ensuremath{-}T/{T}_{c}$. The two lowest orders this produce ${T}_{c}$ standard GL theory. It is shown that agreement with previous studies, theory maps onto single-band model thus fails to describe difference spatial profiles...

We investigate theoretically the temporal behavior of a quantum dot under off-resonant optical excitation targeted at fast acoustic phonon-assisted state preparation. demonstrate that in preparation process driven by short laser pulses three processes can be identified: dressing states during switch on pulse, subsequent phonon-induced relaxation and an undressing end pulse. By analyzing scenarios with different pulse shapes we highlight decisive impact adiabatic final protocols. Furthermore,...

We present a numerical path-integral iteration scheme for the low-dimensional reduced density matrix of time-dependent quantum dissipative system. Our approach simultaneously accounts combined action microscopically modeled pure-dephasing-type coupling to continuum harmonic oscillators representing, e.g., phonons, and further environmental interactions inducing non-Hamiltonian dynamics in inner system represented, by Lindblad-type dissipation or relaxation. formulation method allows...

We demonstrate that the temperature and doping dependencies of photoluminescence (PL) spectra a doped MoS2 monolayer have several peculiar characteristics defined by trion radiative decay. While only zero-momentum exciton states are coupled to light, recombination non-zero momentum trions is also allowed. This leads an asymmetric broadening spectral peak redshift emitted light with increasing temperature. The lowest energy state dark, which manifested sharply non-monotonic dependence PL...

The quantum regression theorem (QRT) is the most widely used tool for calculating multitime correlation functions assessment of emitters. It an approximate method based on a Markov assumption environmental coupling. In this Letter we quantify properties photons emitted from single dot coupled to phonons. For single-photon purity and indistinguishability, compare numerically exact path-integral results with those obtained QRT. demonstrated that QRT systematically overestimates influence...

Based on the Gor'kov formalism for a clean s-wave superconductor, we develop an extended version of single-band Ginzburg-Landau (GL) theory by means systematic expansion in deviation from critical temperature T_c, i.e., tau=1-T/T_c. We calculate different contributions to order parameter and magnetic field: leading (~ tau^1/2 ~ tau field) are controlled standard theory, while next-to-leading terms tau^3/2 gap tau^2 constitute GL (EGL) approach. derive free-energy functional corresponding...

Quantum-size oscillations of the basic physical characteristics a confined fermionic condensate are well-known phenomenon. Its conventional understanding is based on single-particle physics, whereby follow variations in density states driven by size quantization. Here we present study cigar-shaped ultracold superfluid Fermi gas, which demonstrates an important many-body aspect quantum-size coherent effects, overlooked previously. The physics revealed here atypical crossover from...