Israel Bar-Joseph

Israel Bar-Joseph
Weizmann Institute of Science | weizmann · Department of Physics of Condensed Matter

Full Professor

About

185
Publications
9,683
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
7,880
Citations

Publications

Publications (185)
Article
Full-text available
We investigate electrically driven plasmon (EDP) emission in metal-insulator-semiconductor tunnel junctions. We find that amorphization of the silicon crystal at a narrow region near the junction due to the applied voltage plays a critical role in determining the nature of the emission. Furthermore, we suggest that the change in the properties of t...
Article
Full-text available
We show that a Bose-Einstein condensate consisting of dark excitons forms in GaAs coupled quantum wells at low temperatures. We find that the condensate extends over hundreds of micrometers, well beyond the optical excitation region, and is limited only by the boundaries of the mesa. We show that the condensate density is determined by spin-flippin...
Article
Full-text available
We study metal–insulator–semiconductor tunnel junctions where the metal electrode is a patterned gold layer, the insulator is a thin layer of Al2O3, and the semiconductor is p-type silicon. We observe light emission due to plasmon-assisted inelastic tunneling from the metal to the silicon valence band. The emission cutoff shifts to higher energies...
Article
Full-text available
We study the exciton gas-liquid transition in GaAs/AlGaAs coupled quantum wells. Below a critical temperature, Tc=4.8K, and above a threshold laser power density the system undergoes a phase transition into a liquid state. We determine the density temperature phase diagram over the temperature range 0.1 to 4.8K. We find that the latent heat increas...
Preprint
We study the exciton gas-liquid transition in GaAs/AlGaAs coupled quantum wells. Below a critical temperature, Tc=4.8K, and above a threshold laser power density the system undergoes a phase transition into a liquid state. We determine the density temperature phase diagram over the temperature range 0.1 to 4.8K. We find that the latent heat increas...
Article
We present an electrically driven plasmonic device consisting of a gold nanoparticle trapped in a gap between two electrodes. The tunneling current in the device generates plasmons, which decay radiatively. The emitted spectrum extends up to an energy that depends on the applied voltage. Characterization of the electrical conductance at low tempera...
Article
In this work we investigate the dynamics of a single electron surface trap, embedded in a self-assembly metallic double-dot system. The charging and discharging of the trap by a single electron is manifested as a random telegraph signal of the current through the double-dot device. We find that we can control the duration time that an electron resi...
Article
Full-text available
Excitons in semiconductors may form correlated phases at low temperatures. We report the observation of an exciton liquid in GaAs/AlGaAs coupled quantum wells. Above a critical density and below a critical temperature the photogenerated electrons and holes separate into two phases, an electron-hole plasma and an exciton liquid, with a clear sharp b...
Article
We present a self-assembly method to construct CdSe/ZnS quantum dot-gold nanoparticle complexes. This method allows us to form complexes with relatively good control of the composition and structure that can be used for detailed study of the exciton-plasmon interactions. We determine the contribution of the polarization-dependent near-field enhance...
Article
Full-text available
We report optical spectroscopy studies and electrical transport measurements that provide evidence for the formation of a dark exciton condensate in GaAs coupled quantum wells. We find that below a critical temperature and above a threshold power the photoluminescence from the sample separates into two spatial regions, each characterized by a disti...
Article
Full-text available
Resistively detected nuclear magnetic resonance is used to measure the Knight shift of the As nuclei and determine the electron spin polarization of the fractional quantum Hall states of the second Landau level. We show that the 5/2 state is fully polarized within experimental error, thus confirming a fundamental assumption of the Moore-Read theory...
Article
We present an approach that allows forming a nanometric double dot single electron device. It uses chemical synthesis of metallic nanoparticles to form dimeric structures, e-beam lithography to define electrodes and gates, and electrostatic trapping to place the dimers in between the electrodes. We demonstrate a control of its charge configuration...
Article
Full-text available
We apply polarization resolved photoluminescence spectroscopy to measure the spin polarization of a two dimensional electron gas in perpendicular magnetic field. In the vicinity of filling factor nu=5/2, we observe a sharp discontinuity in the energy of the zero Landau level emission line. We find that the splitting between the two circular polariz...
Article
A Reply to the Comment by A. L. Ivanov et al..
Article
We study surface-enhanced Raman scattering (SERS) of individual organic molecules embedded in dimers of two metal nanoparticles. The good control of the dimer preparation process, based on the usage of bifunctional molecules, enables us to study quantitatively the effect of the nanoparticle size on the SERS intensity and spectrum at the single mole...
Article
Full-text available
Optical absorption measurements are used to probe the spin polarization in the integer and fractional quantum Hall effect regimes. The system is fully spin polarized only at filling factor nu=1 and at very low temperatures ( approximately 40 mK). A small change in filling factor (deltanu approximately +/-0.01) leads to a significant depolarization....
Preprint
Optical absorption measurements are used to probe the spin polarization in the integer and fractional quantum Hall effect regimes. The system is fully spin polarized only at filling factor $\nu=1$ and at very low temperatures($\sim40$ mK). A small change in filling factor ($\delta\nu\approx\pm0.01$) leads to a significant depolarization. This sugge...
Article
Full-text available
In this Letter, we study the diffusion properties of photoexcited carriers in coupled quantum wells around the Mott transition. We find that the diffusion of unbound electrons and holes is ambipolar and is characterized by a large diffusion coefficient, similar to that found in p-i-n junctions. Correlation effects in the excitonic phase are found t...
Article
Full-text available
In this work we study the phase diagram of indirect excitons in coupled quantum wells and show that the system undergoes a phase transition to an unbound electron-hole plasma. This transition is manifested as an abrupt change in the photoluminescence linewidth and peak energy at some critical power density and temperature. By measuring the exciton...
Article
We employ a combination of optical UV- and electron-beam-lithography to create an atom chip combining sub-micron wire structures with larger conventional wires on a single substrate. The new multi-layer fabrication enables crossed wire configurations, greatly enhancing the flexibility in designing potentials for ultra cold quantum gases and Bose-Ei...
Article
Potential roughness has been reported to severely impair experiments in magnetic microtraps. We show that these obstacles can be overcome as we measure disorder potentials that are reduced by two orders of magnitude near lithographically patterned high-quality gold layers on semiconductor atom chip substrates. The spectrum of the remaining field va...
Article
Full-text available
We study the absorption spectrum of a two-dimensional electron gas (2DEG) in a magnetic field. We find that at low temps., when the 2DEG is spin polarized, the absorption spectra, which correspond to the creation of spin up or spin down electrons, differ in magnitude, linewidth, and filling factor dependence. We show that these differences can be e...
Article
Full-text available
We present measurements of optical interband absorption in the fractional quantum Hall regime in a GaAs quantum well in the range 0<nu<or=1. We investigate the mechanism of singlet trion absorption, and show that its circular dichroism can be used as a probe of the spin polarization of the ground state of the two-dimensional electron system (2DES)....
Preprint
We study the absorption spectrum of a two-dimensional electron gas (2DEG) in a magnetic field. We find that that at low temperatures, when the 2DEG is spin polarized, the absorption spectra, which correspond to the creation of spin up or spin down electron, differ in magnitude, linewidth and filling factor dependence. We show that these differences...
Article
Full-text available
Radio-Frequency coupling between magnetically trapped atomic states allows to create versatile adiabatic dressed state potentials for neutral atom manipulation. Most notably, a single magnetic trap can be split into a double well by controlling amplitude and frequency of an oscillating magnetic field. We use this to build an integrated matter wave...
Preprint
We present measurements of optical interband absorption in the fractional quantum Hall regime in a GaAs quantum well in the range 0 < nu < 1. We investigate the mechanism of singlet trion absorption, and show that its circular dichroism can be used as a probe of the spin polarization of the ground state of the two-dimensional electron system (2DES)...
Article
We discuss the application of Bose-Einstein condensates (BECs) as sensors for magnetic and electric fields. In an experimental demonstration we have brought one-dimensional BECs close to micro-fabricated wires on an atom chip and thereby reached a sensitivity to potential variations of ~10e-14eV at 3 micron spatial resolution. We demonstrate the ve...
Conference Paper
Coherent manipulation of matter waves in microscopic trapping potentials facilitates both fundamental and technological applications. Here we focus on experiments with a microscopic integrated interferometer that demonstrate coherent operation on an atom chip.
Article
Magnetic trapping potentials for atoms on atom chips are determined by the current flow in the chip wires. By modifying the shape of the conductor we can realize specialized current flow patterns and therefore micro-design the trapping potentials. We have demonstrated this by nano-machining an atom chip using the focused ion beam technique. We buil...
Article
We measure the spin polarization of a two-dimensional electron system (2DES) in the Quantum Hall regime by photocurrent interband absorption spectroscopy. The sample is a single GaAs quantum well that is placed in a dilution fridge with optical windows at low temperatures down to 70 mK. The 2DES density is tuned by a back-gate. We illuminate with c...
Article
The near band edge absorption spectrum of a quantum well which contains an electron gas is studied. We show that electron–hole correlations play an important role in determining this spectrum. At zero magnetic field the spectrum evolves with increasing electron density from being dominated by neutral excitons at the very dilute limit to charged exc...
Article
Matter-wave interference experiments enable us to study matter at its most basic, quantum level and form the basis of high-precision sensors for applications such as inertial and gravitational field sensing. Success in both of these pursuits requires the development of atom-optical elements that can manipulate matter waves at the same time as prese...
Article
Microscopic atom optical devices integrated on atom chips allow to precisely control and manipulate ultra-cold (T < 1 µK) neutral atoms and Bose-Einstein condensates (BECs) close to surfaces. The relevant energy scale of a BEC is extremely small (down to < 10−11 eV). Consequently, BECs can be utilized as a sensor for variations of the potential ene...
Article
Full-text available
Electrical conduction through molecules depends critically on the delocalization of the molecular electronic orbitals and their connection to the metallic contacts. Thiolated (- SH) conjugated organic molecules are therefore considered good candidates for molecular conductors: in such molecules, the orbitals are delocalized throughout the molecular...
Article
We present atom chip traps and guides created by a combination of two current-carrying wires and a bias field pointing perpendicular to the chip surface. These elements can be arranged in any orientation on the chip surface. We study loading schemes for the traps and present a detailed study of the guiding of thermal atomic clouds in an omnidirecti...
Conference Paper
Full-text available
The paper gives an overview of the experiments performed studying the manipulation of both thermal atoms and Bose-Einstein condensates (BEC) on atom chips.
Article
Today's magnetic-field sensors are not capable of making measurements with both high spatial resolution and good field sensitivity. For example, magnetic force microscopy allows the investigation of magnetic structures with a spatial resolution in the nanometre range, but with low sensitivity, whereas SQUIDs and atomic magnetometers enable extremel...
Article
The emission and absorption spectra of quantum wells containing electron or hole gas are reviewed. We show that trions, also known as charged excitons, play a dominant role in determining these spectra. We discuss issues related to their behaviour at zero and high magnetic fields, their far-field and near-field spectra, and their role as a probe fo...
Conference Paper
Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime and potential obstacles and solutions. We show that...
Article
Neutral atoms can be trapped and manipulated with surface mounted microscopic current carrying and charged structures. We present a lithographic fabrication process for such atom chips based on evaporated metal films. The size limit of this process is below 1$\mu$m. At room temperature, thin wires can carry more than 10$^7$A/cm$^2$ current density...
Article
Full-text available
We present an omnidirectional matter waveguide on an atom chip. The guide is based on a combination of two current-carrying wires and a bias field pointing perpendicular to the chip surface. Thermal atoms are guided for more than two complete turns along a 25-mm-long spiral path (with curve radii as short as 200 µ m ) at various atom-surface distan...
Article
We measure the absorption spectrum of a two-dimensional electron system (2DES) in a GaAs quantum well in the presence of a perpendicular magnetic field. We focus on the absorption spectrum into the lowest Landau level around nu=1. We find that the spectrum consists of bound electron-hole complexes, trionlike and excitonlike. We show that their osci...
Article
Full-text available
Microscopic flows are almost universally linear, laminar, and stationary because the Reynolds number, Re, is usually very small. That impedes mixing in microfluidic devices, which sometimes limits their performance. Here, we show that truly chaotic flow can be generated in a smooth microchannel of a uniform width at arbitrarily low Re, if a small a...
Article
We report on experiments with cold thermal $^{7}\mathrm{L}\mathrm{i}$ atoms confined in combined magnetic and electric potentials. A novel type of three-dimensional trap was formed by modulating a magnetic guide using electrostatic fields. We observed atoms trapped in a string of up to six individual such traps, a controlled transport of an atomic...
Article
We study the photoluminescence (PL) spectrum of a two-dimensional electron system at the high magnetic field limit, where all electrons reside at the lowest Landau level (nu < 2). Using a gated structure we tune the electron density from the dilute limit to a dense electron gas, and follow the changes in the emission spectrum. We find that the spec...
Article
Strong resonant enhancements of inelastic light scattering from the long wavelength inter-Landau level magnetoplasmon and the intra-Landau level spin wave excitations are seen for the fractional quantum Hall state at ν=1/3. The energies of the sharp peaks (FWHM 0.2 meV) in the profiles of resonant enhancement of inelastic light scattering intensiti...
Article
We describe an experiment to create a sizable 87Rb Bose–Einstein condensate (BEC) in a simple magnetic microtrap, created by a current through a Z-shaped wire and a homogeneous bias field. The BEC is created close to a reflecting surface. It is an ideal coherent source for experiments with cold atoms close to surfaces, be it small-volume microtraps...
Article
We present a novel method for fabrication of contacts to nanosize particles. The method is based on conventional optical lithography of GaAs/AlGaAs molecular beam epitaxy grown structures. Taking ad vantage of the difference in etch rate between GaAs and AlGaAs a narrow gap is formed between metal contacts deposited on the side of a mesa structure....
Article
We present a new method for bridging the gap between the nanometer scale of molecules and the micrometer scale achievable using conventional micro and e-beam lithography techniques. A single dithiolated organic molecule is chemically connected to two nano gold clusters that serve as ohmic contacts thus forming a cluster - molecule - cluster dimmer...
Article
A Bose-Einstein condensate is created in a simple and robust miniature Ioffe-Pritchard trap, the so-called Z trap. This trap follows from the mere combination of a Z-shaped current carrying wire and a homogeneous bias field. The experimental procedure allows condensation of typically 3x10^5 Rb-87 atoms in the |F=2, m_F=2> state close to any mirrori...
Article
Full-text available
Variations in the width of a quantum well (QW) are known to be a source of broadening of the exciton line. Using low temperature near-field optical microscopy, we have exploited the dependence of exciton energy on well width to show that in GaAs QWs, these seemingly random well-width fluctuations actually exhibit well-defined order-strong long-rang...
Article
We present an experimental and theoretical microscopic view on the optical trion spectrum in the presence of disorder. Although strong spatial fluctuations in near-field spectra point to strongly localized trion states, the far-field spectrum reveals the contribution of weakly localized trion states in addition. It is shown, that the underlying phy...
Preprint
Full-text available
Variations in the width of a quantum well (QW) are known to be a source of broadening of the exciton line. Using low temperature near-field optical microscopy, we have exploited the dependence of exciton energy on well-width to show that in GaAs QWs, these seemingly random well-width fluctuations actually exhibit well-defined order -- strong long-r...
Article
Full-text available
Nano-size objects like metal clusters present an ideal system for the study of quantum phenomena and for constructing practical quantum devices. Integrating these small objects in a macroscopic circuit is, however, a difficult task. So far the nanoparticles have been contacted and addressed by highly sophisticated techniques which are not suitable...
Article
We present a microscopic understanding of the underlying physics that governs the photoluminescence spectrum at low electron densities. By performing near- and far-field measurements we show how the various characteristics of the spectrum (intensity, energy, width) are affected by the background electron density and the potential fluctuations due t...
Article
Full-text available
We use low temperature near-field optical spectroscopy to image the electron density distribution in the plane of a high mobility GaAs quantum well. We find that the electrons are not randomly distributed in the plane, but rather form narrow stripes (width smaller than 150 nm) of higher electron density. The stripes are oriented along the [1-10 ] c...
Article
We study the photoluminescence spectrum of a low density (v < 1) two-dimensional electron gas at high magnetic fields and low temperatures. We find that the spectrum in the fractional quantum Hall regime can be understood in terms of singlet and triplet charged-excitons. We identify the dark triplet charged-exciton and show that it is visible in th...
Article
We study the photoluminescence spectrum of a low-density (nu<1) two-dimensional electron gas at high magnetic fields and low temperatures. We find that the spectrum in the fractional quantum Hall regime can be understood in terms of singlet and triplet charged excitons. We show that these spectral lines are sensitive probes for the electron compres...
Article
Full-text available
The near- and far-field photoluminescence (PL) spectra of a gated two-dimensional electron gas have been measured in a GaAs quantum well. Scanning near-field measurements reveal the microscopic origin of the different line shapes of the neutral (X) and negatively charged (X-) exciton. We find a new broadening mechanism of the exciton: local density...
Article
We study the low-energy tail of the photoluminescence spectrum of a low-density two-dimensional hole gas in a magnetic field in a GaAs quantum well. A rich spectrum of lines is observed, and we show that it can be classified into two groups: the shake-up lines of the positively charged exciton (X+), and the recombination lines of a free hole with a...
Preprint
We study the photoluminescence spectrum of a low density ($\nu <1$) two-dimensional electron gas at high magnetic fields and low temperatures. We find that the spectrum in the fractional quantum Hall regime can be understood in terms of singlet and triplet charged-excitons. We show that these spectral lines are sensitive probes for the electrons co...
Article
We show that optical excitation of a wide GaAs quantum well, which is located close to the sample surface, can give rise to the creation of a high-density two-dimensional hole gas in the well. Based on this mechanism, we present a double quantum well structure in which spatially separated electron and hole gases are optically created at close proxi...
Article
We demonstrate the feasibility of monolithic integration of a quantum-well infrared detector and a read-out circuit on the same GaAs/AlGaAs crystal. Charge storage capability of 2×107 electrons in a 50×50 μm2 pixel is obtained. The operation of a 5×5 test array is reported, performing all the basic functions of a practical focal plane array. © 2001...
Article
A near-field scanning optical microscope for operation within a storage Dewar is described. It was designed for studies of opaque samples and operates in the collection mode. Illumination can be either through the tip or from the side via a separate fiber. Scans can be begun within 2 h after start of cooldown. Its rigid design allows high resolutio...
Article
Full-text available
We study the evolution of the absorption spectrum of a modulation doped GaAs/AlGaAs semiconductor quantum well with decreasing the carrier density. We find that there is a critical density which marks the transition from a Fermi edge singularity to a hydrogen-like behavior. At this density both the lineshape and the transitions energies of the exci...
Chapter
We study the dependence of the photoluminescence decay of the negatively charged exciton on the electron concentration for different excitation energies. The radiative lifetime of the trion, directly measured when exciting the trion resonantly, is found to be constant for the studied concentration range from about 3 x 1010 cm-2 upwards.
Chapter
We study the spatial distribution of the photoluminescence of a gated two-dimensional electron gas with sub-wavelength resolution. This is done by scanning a tapered Optical fibre tip with an aperture of 250 nm in the near field region of the sample surface, and collecting the photoluminescence. The spectral line of the negatively charged exciton,...
Article
We determine the exciton exchange splitting in a wide GaAs quantum well. Our method is based on applying a magnetic field parallel to the layers and measuring the oscillator strength ratio of the Zeeman split lines in two linear polarizations. We develop a theoretical model to describe the effect of the magnetic field on the exciton spectrum, and u...
Article
We compare the photoluminescence spectra of the negatively and positively charged excitons in GaAs quantum wells. We use a structure which enables us to observe both complexes within the same sample. We find that their binding energy and Zeeman splitting are very similar at zero magnetic field, but evolve very differently at high fields. We discuss...
Article
We report on time-resolved photoluminescence studies of charged and neutral excitons in a modulation doped GaAs quantum well under resonant excitation and high magnetic field. The radiative lifetime of the charged exciton is rather short, 60 ps at zero held, and is found to increase by a factor of similar to 2 up to 7 T. The short lifetimes suggest...
Article
Full-text available
We study the dynamics of the charged and neutral excitons in a modulation-doped GaAs quantum well by time-resolved photoluminescence under a resonant excitation. The radiative lifetime of the charged exciton is found to be surprisingly short, 60 ps. This time is temperature independent between 2 and 10 K, and increases by a factor of 2 at 6 T. We d...
Article
Full-text available
The near-field photoluminescence of a gated two-dimensional electron gas is measured. We use the negatively charged exciton, formed by binding of an electron to a photo-excited electron-hole pair, as an indicator for the local presence of charge. Large spatial fluctuations in the luminescence intensity of the negatively charged exciton are observed...
Article
The time-resolved secondary emission of resonantly created excitons in GaAs quantum wells is studied using femtosecond up-conversion spectroscopy. The behaviour of the rise and decay of the secondary emission and reflectivity in quantum welts is strongly dependent upon the disorder at the interfaces, the exciton density and the temperature. In the...
Article
Full-text available
We have studied the conductivity peak in the transition region between the two lowest integer Quantum Hall states using transmission measurements of edge magnetoplasmons. The width of the transition region is found to increase linearly with frequency but remains finite when extrapolated to zero frequency and temperature. Contrary to prevalent theor...
Article
Shake-up processes in the photoluminescence spectra of a two-dimensional electron gas in a GaAs/AlGaAs quantum well at high magnetic fields are studied at a range of filling factors. We find that when the electrons occupy only the lowest Landau level these processes are strongly suppressed. A peculiar dependence of a giant `zeroth' shake-up line on...
Article
Full-text available
We have improved the sensitivity and signal-to-noise ratio of a luminescence upconversion experiment, using a charge-coupled device (CCD) as the detector. We show experimentally and numerically that the bandwidth of a 1-mm-thick β-barium borate crystal is large enough to take full advantage of the multichannel capabilities of the CCD. The improveme...
Article
We report the fabrication and testing of an all-GaAs/AlGaAs hybrid readout circuit operating at 77 K designated for use with an GaAs/AlGaAs background-limited quantum-well infrared photodetector focal plane array (QWIP FPA). The circuit is based on a direct injection scheme, using specially designed cryogenic GaAs/AlGaAs MODFET's and a novel n<sup>...
Article
We observe shakeup processes in the photoluminescence spectra of a two-dimensional electron gas in a ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{x}{\mathrm{Ga}}_{1$-${}x}\mathrm{As}$ quantum well at high magnetic fields. We find that when the electrons occupy only the lowest Landau level these processes are strongly suppressed...
Conference Paper
Luminescence has been quite widely used for the study of semiconductor nanostructures, and more especially time resolved luminescence, due to the ease to get a luminescence signal. The interpretation of the results however is sometimes quite complex, and one generally finds that some care has to be taken for the results to be meaningful. In particu...