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Phase transitions in micropillar samples.: (a,b) Emission pattern and the integrated PL intensity of the 5 μm round pillar at B = 6 T. In (b) spectral integration has been performed over the polariton lasing peak (black circles) and photon laser peak (red circles), for details see Supplementary material. The arrows indicate the onset and offset of the polariton laser (LP1 and LP2) and the photon laser threshold (C). (c) Phase diagram of a 5 μm round pillar. The red circles correspond to the photon lasing threshold (C), the blue squares show the onset of polariton lasing (LP1). The offset of polariton lasing (L2) is shown only indicatively by the boundary between green color and white-green stripes. We cannot extract this threshold from the data with a high accuracy. Note that the polariton lasing transition for zero field reported in c corresponds to a pump power intermediate between those considered in a,b. The lines show the results of simulation. White horizontal bands mark the polariton gas regime, beyond the offset of polariton lasing.
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Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also...
Citations
... Many-body interactions of charge carriers in quantum and spatially confined semiconducting nanostructures are enhanced relative to their bulk counterparts and thus have opened new opportunities for manipulating and enhancing light-matter interactions [1][2][3][4][5]. From a fundamental point of view, the enhanced Coulomb interactions due to the lowdimensional confinement endow carrier-carrier interactions, predicted to generate exotic effects such as exciton complexes [2,[6][7][8][9], Mott transitions [4,[10][11][12], bandgap renormalization (BGR) [4,13], charge density waves [14,15], and Bose-Einstein and Fermionic condensates [16,17]. Among these, BGR, a many-body effect described as a lowering of the fundamental bandgap with increasing free-carrier density [4,13], is of particular importance as it provides insight into the feasibility of utilizing nanostructures in various optoelectronic and photonic applications such as optical switches, saturable absorbers, and modulators [13]. ...
The spin-dependence of the strongly correlated phenomena and many-body interactions play an important role in quantum information science. In particular, it is quite interesting but unclear how the spin degree of freedom ramifies the bandgap renormalization, one of the fundamental many-body phenomena. We report the first room-temperature observation of giant spin-selective bandgap renormalization (SS-BGR) in CsPbBr3 colloidal nanocrystals using time-resolved circularly polarized femtosecond pump-probe spectroscopy. The SS-BGR results from many-body interactions among carriers with the same spin that renormalize their joint density of states by 57± 1 meV, visualized here as photoinduced absorption (PIA) below band-edge transition energy when the pump and probe are co-polarized. The hallmark result of spectrally resolved SS-BGR is in stark contrast to the usually submerged signal in II-VI and III-V semiconductors and is 3 orders of magnitude larger than that observed in Ge/SiGe quantum wells, highlighting the unique and beneficial band structure of the metal-halide semiconductors. We propose that the PIA, due to SS-BGR, can be used to describe the spin-polarization and spin-relaxation dynamics. The experimental and theoretical findings open up new possibilities for optical manipulation of spin degrees of freedom and their many-body interactions in metal-halide perovskite nanocrystals for potential room-temperature applications.
... However, the exciton formation can be slowed down when the phonon energy is much smaller than the exciton binding energy, 26 or when diffusion of photogenerated electrons and hole brings them too far from each other as compared to the Bohr radius of excitons. 27 Thus, if the exciton formation from the hot carriers is slower than their interband or trap-assisted recombination, one should observe the domination of free carriers and the dependence of PL QY on carrier concentrations. The PL spectrum is also dependent on the type of dominating carriers, being blue-shifted in the case of free-carrier domination and red-shifted when excitons' contribution is stronger, as schematically shown in Figure 1a. ...
... In previous studies, the magnetic field applied in Faraday geometry enabled lowering of the polariton condensation threshold 31,32 or, when applied in the Voigt geometry, controlling of the polariton condensate propagation in single microcavities 33 . Here, we demonstrate photon-mediated exciton interaction and energy transfer between the macroscopically distant QWs in double microcavity structure and use the magnetic field as a mean to control of the transfer direction. ...
Coupling of quantum emitters in a semiconductor relies, generally, on short-range dipole-dipole or electronic exchange type interactions. Consistently, energy transfer between exciton states, that is, electron-hole pairs bound by Coulomb interaction, is limited to distances of the order of 10 nm. Here, we demonstrate polariton-mediated coupling and energy transfer between excitonic states over a distance exceeding 2 μm. We accomplish this by coupling quantum well-confined excitons through the delocalized mode of two coupled optical microcavities. Use of magnetically doped quantum wells enables us to tune the confined exciton energy by the magnetic field and in this way to control the spatial direction of the transfer. Such controlled, long-distance interaction between coherently coupled quantum emitters opens possibilities of a scalable implementation of quantum networks and quantum simulators based on solid-state, multi-cavity systems.
... In previous studies, the magnetic field applied in Faraday geometry enabled lowering of the polariton condensation threshold 31,32 or, when applied in the Voigt geometry, controlling of the polariton condensate propagation in single microcavities 33 . Here, we demonstrate photon-mediated exciton interaction and energy transfer between the macroscopically distant QWs in double microcavity structure and use the magnetic field as a mean to control of the transfer direction. ...
Coupling of quantum emitters in a semiconductor relies, generally, on short-range dipole-dipole or electronic exchange type interactions. Consistently, energy transfer between exciton states, that is, electron-hole pairs bound by Coulomb interaction, is limited to distances of the order of 10~nm. Here, we demonstrate polariton-mediated coupling and energy transfer between excitonic states over a distance exceeding 2~$\mu$m. We accomplish this by coupling quantum well-confined excitons through the delocalized mode of two coupled optical microcavities. Use of magnetically doped quantum wells enables us to tune the confined exciton energy by the magnetic field and in this way to control the spatial direction of the transfer. Such controlled, long-distance interaction between coherently coupled quantum emitters opens possibilities of a scalable implementation of quantum networks and quantum simulators based on solid-state, multi-cavity systems.
... In solid state systems, bosons can undergo a phase transition to a Bose-Einstein condensate (BEC), which has been reported in GaAs [8] and MoS 2 materials [9]. In a hybrid system containing a BEC, there can appear magnetically controlled lasing, the Mott phase transition from an ordered state to electron-hole plasma [10], giant Fano resonances [11], which are also shown to occur for superconductor hybrids [12], and supersolidity [13]. Returning to the fermionic subsystem, studies of the electron transport in 2DEG have many technological applications, especially in the context of interface physics [14][15][16], where 2DEG exhibits rich phenomena such as the anomalous magnetoresistance and the Hall effect [17][18][19], two-dimensional metallic conductivity [20,21], superconductivity, and ferromagnetism [22][23][24][25]. ...
... Let us consider the system presented in Fig. 1, consisting of a 2DEG with parabolic dispersion of electrons and a layer of the Bose-condensed exciton gas [8,44]. The two layers are spatially separated and coupled by the Coulomb interaction [10,11,13], described by the ...
We report on the novel mechanism of electron scattering in hybrid Bose-Fermi systems consisting of a two-dimensional electron gas in the vicinity of an exciton condensate: We show that a pair-of-bogolons-mediated scattering proves to be dominating over the conventional acoustic phonon channel and over the single-bogolon scattering, even if the screening is taken into account. We develop a microscopic theory of this effect, focusing on GaAs and MoS2 materials, and find the principal temperature dependence of resistivity, distinct from the conventional phonon-mediated processes. Further, we scrutinize parameters and suggest a way to design composite samples with predefined electron mobilities and propose a mechanism of electron pairing for superconductivity. Hybrid Bose-Fermi systems essentially represent a layer of fermions, usually two-dimensional electron gas (2DEG), coupled to another layer of bosons, such as excitons, exciton polaritons, or Cooper pairs. The interplay between Bose and Fermi particles leads to various novel fascinating phenomena, interesting from both the technological and fundamental physics perspectives. For instance, in a hybrid two-dimensional electron gas-superconductor system it became possible to realize the long-sought Majorana fermion [1-4]. There were also proposed new mechanisms of electron pairing [5] in a hybrid setup involving exciton polaritons in a semiconductor microcavity, opening a possibility for optically controlled superconductivity [6]. Furthermore, the interplay between the polaritons and phonons can enhance the critical temperature of the superconductor [7]. These results pave the way for the realization of a high-temperature conventional BCS superconductivity. In solid state systems, bosons can undergo a phase transition to a Bose-Einstein condensate (BEC), which has been reported in GaAs [8] and MoS 2 materials [9]. In a hybrid system containing a BEC, there can appear magnetically controlled lasing, the Mott phase transition from an ordered state to electron-hole plasma [10], giant Fano resonances [11], which are also shown to occur for superconductor hybrids [12], and supersolidity [13]. Returning to the fermionic subsystem, studies of the electron transport in 2DEG have many technological applications , especially in the context of interface physics [14-16], where 2DEG exhibits rich phenomena such as the anomalous magnetoresistance and the Hall effect [17-19], two-dimensional metallic conductivity [20, 21], supercon-ductivity, and ferromagnetism [22-25]. Electron scattering on acoustic phonons and disorder plays a major role in all these phenomena [26-38]. However, the emerging topic of combining a 2DEG h l d ē ē. 2DEG FIG. 1. System schematic. Bogolon-mediated electron scattering in 2DEG located at the distance l from a two-dimensional dipolar exciton gas, residing in two parallel layers , which are at the distance d from each other. The particles are coupled via the Coulomb interaction. with a BEC demands the study of the electron transport in hybrid systems and forces us to confront new types of interactions beyond the conventional phonon and impurity channels [39-41]. In this Letter, we reexamine the electron transport in hybrid systems and report on the unconventional mechanism of the electron scattering which is due to the interaction with the Bogoliubov exci-tations or bogolons [42, 43]. The bogolons represent ex-citations over the BEC and, similar to acoustic phonons, have a linear spectrum at small momenta. While one may naively argue that the bogolon scattering should be similar to the phonon-assisted case, with the acoustic phonon sound velocity simply replaced by the bogolon sound velocity, we will show that this is not at all the case and the difference turns out fundamental. Let us consider the system presented in Fig. 1, consisting of a 2DEG with parabolic dispersion of electrons and a layer of the Bose-condensed exciton gas [8, 44]. The two layers are spatially separated and coupled by the Coulomb interaction [10, 11, 13], described by the
... In solid state systems, bosons can undergo a phase transition to a Bose-Einstein condensate (BEC), which has been reported in GaAs [8] and MoS 2 materials [9]. In a hybrid system containing a BEC, there can appear magnetically controlled lasing, the Mott phase transition from an ordered state to electron-hole plasma [10], giant Fano resonances [11], which are also shown to occur for superconductor hybrids [12], and supersolidity [13]. Returning to the fermionic subsystem, studies of the electron transport in 2DEG have many technological applications, especially in the context of interface physics [14][15][16], where 2DEG exhibits rich phenomena such as the anomalous magnetoresistance and the Hall effect [17][18][19], two-dimensional metallic conductivity [20,21], superconductivity, and ferromagnetism [22][23][24][25]. ...
... Let us consider the system presented in Fig. 1, consisting of a 2DEG with parabolic dispersion of electrons and a layer of the Bose-condensed exciton gas [8,44]. The two layers are spatially separated and coupled by the Coulomb interaction [10,11,13], described by the arXiv:1902.01214v1 [cond-mat.mes-hall] ...
We report on the novel mechanism of electron scattering in hybrid Bose-Fermi systems consisting of a two-dimensional electron gas in the vicinity of an exciton condensate: We show that a pair-of-bogolons--mediated scattering proves to be dominating over the conventional acoustic phonon channel and over the single-bogolon scattering, even if the screening is taken into account. We develop a microscopic theory of this effect, focusing on GaAs and MoS$_2$ materials, and find the principal temperature dependence of resistivity, distinct from the conventional phonon--mediated processes. Further, we scrutinize parameters and suggest a way to design composite samples with predefined electron mobilities and propose a mechanism of electron pairing for superconductivity.
... Hybrid systems consist of two-dimensional spatially separated layers, containing electrons in a two-dimensional electron gas (2DEG) phase and bosons, such as direct and indirect (dipolar) excitons, exciton polaritons, or the Cooper pairs in superconductors [15]. In these systems, the research is, on the one hand, devoted to high-temperature boson-mediated superconductivity [16] and other condensation phenomena in interacting structures, including the Mott phase transition from an ordered state to electron-hole plasma [17]. On the other hand, in such systems there can appear new mechanisms of scattering of fermions in the 2DEG, thus modifying the temperature dependence of the kinetic coefficients. ...
... In this Letter, we show that in hybrid Bose-Fermi systems, which consist of spatially separated 2DEG in graphene layer and an exciton gas, interacting via the Coulomb forces [17][18][19], there appears a counterpart to the phonon-mediated scattering, when the gas of bosons is condensed [20][21][22]. Two-dimensional condensation has been reported in various solid state systems [23][24][25]. ...
... and the subscript k F in the expression (Γ − − Γ + ) k F in (17) means that all the electron wave vectors p are to be substituted by k F there. For temperatures much lower than the Bloch-Grüneisen temperature, we find the following expression, ...
We report on an unconventional mechanism of electron scattering in graphene in hybrid Bose- Fermi systems. We study energy-dependent electron relaxation time, accounting for the processes of emission and absorption of a Bogoliubov excitation (a bogolon). Then using the Bloch-Gruneisen approach, we find the finite-temperature resistivity of graphene and show that its principal behavior is $\sim T^4$ in the limit of low temperatures and linear at high temperatures. We show that bogolon-mediated scattering can surpass the acoustic phonon-assisted relaxation. It can be controlled by the distance between the layers and the condensate density, giving us additional degrees of freedom and a useful tool to render electron mobility by the sample design and external pump.
... A full diamagnetic screening of the external magnetic field from the material interior (Meissner effect) and a suppression of superfluidity was predicted. Few experimental works followed this prediction [17][18][19][20][21] , but the polariton Zeeman splitting in typical III-V or II-VI based microcavities is very low, of approx. 100 μeV at 5 T, being within the range of polariton emission linewidth, which makes the interpretation of the results very difficult. ...
Owing to their integer spin, exciton-polaritons in microcavities can be used for observation of non-equilibrium Bose-Einstein condensation in solid state. However, spin-related phenomena of such condensates are difficult to explore due to the relatively small Zeeman effect of standard semiconductor microcavity systems and the strong tendency to sustain an equal population of two spin components, which precludes the observation of condensates with a well defined spin projection along the axis of the system. The enhancement of the Zeeman splitting can be achieved by introducing magnetic ions to the quantum wells, and consequently forming semimagnetic polaritons. In this system, increasing magnetic field can induce polariton condensation at constant excitation power. Here we evidence the spin polarization of a semimagnetic polaritons condensate exhibiting a circularly polarized emission over 95% even in a moderate magnetic field of about 3 T. Furthermore, we show that unlike nonmagnetic polaritons, an increase on excitation power results in an increase of the semimagnetic polaritons condensate spin polarization. These properties open new possibilities for testing theoretically predicted phenomena of spin polarized condensate.
... In order to better understand fundamental properties of this phenomenon, it is important to separate the BEC from the conduction electrons and study the influence of different interactions separately. One of the recent active areas of research is hybrid Bose-Fermi systems which consist of two-dimensional (2D) spatially separated electron and exciton gases, interacting with each other via the Coulomb forces [16][17][18][19][20]. These systems can be a testbed for various physical phenomena, some of which occur when the exciton (or exciton-polariton) gas is in the BEC regime [21]. ...
We investigate the processes of electron capture by a Coulomb impurity center residing in a hybrid system consisting of spatially separated two-dimensional layers of electron and Bose-condensed dipolar exciton gases coupled via the Coulomb forces. We calculate the probability of the electron capture accompanied by the emission of a single Bogoliubov excitation (bogolon), similar to regular phonon-mediated scattering in solids. Further, we study the electron capture mediated by the emission of a pair of bogolons in a single capture event and show that these processes not only should be treated in the same order of the perturbation theory, but also they give more important contribution than single bogolon-mediated capture, in contrast with regular phonon scattering. As a result, electric conductivity can be dramatically modified in the presence of charged impurities.
... The magnetic field causes a diamagnetic shift and a Zeeman splitting of exciton states, which have been widely studied for bulk crystals [1,2] and single quantum wells (QWs) [3][4][5][6]. Coupling of excitons with light in a QW embedded in a microcavity is found to be very sensitive to the application of magnetic field [7][8][9][10][11][12][13]. Many works have been devoted to indirect excitons in double-QW structures in magnetic field, whose long lifetime allows one to study, in particular, their dipole-dipole interaction [14,15] and transport across the magnetic field [16][17][18]. ...
... The experimental data processing shows that the nonradiative broadenings ¯ hh j are almost independent of the magnetic field within the experimental error: ¯ hh 1 = 54 ± 2 μeV (for B = 0. .. 4 T), ¯ hh 2 = 73 ± 4 μeV, ¯ hh 3 = 73 ± 10 μeV, and ¯ hh 4 = 83 ± 5 μeV. The exception is the increase of ¯ hh 1 from 54 to 65 μeV when the magnetic field increases from 4 to 6 T. The broadening increase is possibly caused by a suppression of the electron diffusion from the excited area of the sample [11]. The phase shift obtained in the fits are also almost insensitive to the magnetic field. ...
We report on the observation of a significant increase of the radiative decay rates for exciton transitions in a wide (In,Ga)As/GaAs quantum well (L=95 nm) in magnetic fields up to 6 T applied along the growth axis of the heterostructure. The absolute values of the radiative decay rates are obtained from a quantitative analysis of resonant features in the experimentally measured reflectance spectra in the range of the optical transitions to the quantum-confined exciton states. High crystalline quality of the heterostructure allows us to observe the ground and several excited exciton transitions with the nonradiative broadening comparable to the radiative one. We employ a numerical procedure appropriate for the studied wide quantum well to model the increase of the radiative decay rate in magnetic field. The results of the modeling agree well with the experimental data.
