Showing papers on "Stark effect published in 2018"
Monash University, Clayton campus1, Australian Synchrotron2, Singapore University of Technology and Design3, University of Illinois at Urbana–Champaign4, National University of Singapore5, Academy of Sciences of the Czech Republic6, Lawrence Berkeley National Laboratory7, Korea Institute of Science and Technology8, Yale-NUS College9, Nanjing Normal University10
TL;DR: The large bandgaps in both the conventional and quantum spin Hall phases, much greater than the thermal energy at room temperature, suggest that ultrathin Na3Bi is suitable for room-temperature topological transistor operation.
Abstract: The electric-field-induced quantum phase transition from topological to conventional insulator has been proposed as the basis of a topological field effect transistor1-4. In this scheme, 'on' is the ballistic flow of charge and spin along dissipationless edges of a two-dimensional quantum spin Hall insulator5-9, and 'off' is produced by applying an electric field that converts the exotic insulator to a conventional insulator with no conductive channels. Such a topological transistor is promising for low-energy logic circuits4, which would necessitate electric-field-switched materials with conventional and topological bandgaps much greater than the thermal energy at room temperature, substantially greater than proposed so far6-8. Topological Dirac semimetals are promising systems in which to look for topological field-effect switching, as they lie at the boundary between conventional and topological phases3,10-16. Here we use scanning tunnelling microscopy and spectroscopy and angle-resolved photoelectron spectroscopy to show that mono- and bilayer films of the topological Dirac semimetal3,17 Na3Bi are two-dimensional topological insulators with bulk bandgaps greater than 300 millielectronvolts owing to quantum confinement in the absence of electric field. On application of electric field by doping with potassium or by close approach of the scanning tunnelling microscope tip, the Stark effect completely closes the bandgap and re-opens it as a conventional gap of 90 millielectronvolts. The large bandgaps in both the conventional and quantum spin Hall phases, much greater than the thermal energy at room temperature (25 millielectronvolts), suggest that ultrathin Na3Bi is suitable for room-temperature topological transistor operation.
169 citations
TL;DR: By fabricating van der Waals heterostructures of h-BN and graphene, this work demonstrates the electrical control of single-photon emission from atomic defect emitters via the Stark effect and found field-induced discrete modification and stabilization of emission intensity, which were reversibly controllable with an external electric field.
Abstract: Single-photon emitters play an essential role in quantum technologies, including quantum computing and quantum communications. Atomic defects in hexagonal boron nitride (h-BN) have recently emerged as new room-temperature single-photon emitters in solid-state systems, but the development of scalable and tunable h-BN single-photon emitters requires external methods that can control the emission energy of individual defects. Here, by fabricating van der Waals heterostructures of h-BN and graphene, we demonstrate the electrical control of single-photon emission from atomic defects in h-BN via the Stark effect. By applying an out-of-plane electric field through graphene gates, we observed Stark shifts as large as 5.4 nm per GV/m. The Stark shift generated upon a vertical electric field suggests the existence of out-of-plane dipole moments associated with atomic defect emitters, which is supported by first-principles theoretical calculations. Furthermore, we found field-induced discrete modification and stabil...
150 citations
TL;DR: Highly tunable interlayer excitons by an out-of-plane electric field in homobilayers of transition metal dichalcogenides are demonstrated and paved the way for the realization of degenerate exciton gases in atomically thin semiconductors.
Abstract: van der Waals heterostructures formed by stacking two-dimensional atomic crystals are a unique platform for exploring new phenomena and functionalities. Interlayer excitons, bound states of spatially separated electron–hole pairs in van der Waals heterostructures, have demonstrated potential for rich valley physics and optoelectronics applications and been proposed to facilitate high-temperature superfluidity. Here, we demonstrate highly tunable interlayer excitons by an out-of-plane electric field in homobilayers of transition metal dichalcogenides. Continuous tuning of the exciton dipole from negative to positive orientation has been achieved, which is not possible in heterobilayers due to the presence of large built-in interfacial electric fields. A large linear field-induced redshift up to ∼100 meV has been observed in the exciton resonance energy. The Stark effect is accompanied by an enhancement of the exciton recombination lifetime by more than two orders of magnitude to >20 ns. The long recombinat...
122 citations
TL;DR: The role of excitons and excitonic resonances in the optical properties of lead-halide perovskite semiconductors is discussed and how the strong light-matter interactions induce an optical stark effect splitting the doubly spin degenerate ground exciton states is discussed.
Abstract: The exciton binding energy in methylammonium lead iodide (MAPbI3) is about 10 meV, around 1/3 of the available thermal energy (kBT ∼ 26 meV) at room temperature. Thus, exciton populations are not stable at room temperature at moderate photoexcited carrier densities. However, excitonic resonances dominate the absorption onset. Furthermore, these resonances determine the transient absorbance and transient reflectance spectra. The exciton binding energy is a reflection of the Coulomb interaction energy between photoexcited electrons and holes. As such, it serves as a marker for the strength of electron/hole interactions and impacts a variety of phenomena, such as, absorption, radiative recombination, and Auger recombination. In this Perspective, we discuss the role of excitons and excitonic resonances in the optical properties of lead-halide perovskite semiconductors. Finally, we discuss how the strong light–matter interactions induce an optical stark effect splitting the doubly spin degenerate ground excito...
97 citations
83 citations
TL;DR: Large Stark effects in easily made layered hybrid perovskites and a modulation mechanism related to the orientational polarizability of dipolar cations confined within these self-assembled quantum wells are presented.
Abstract: The quantum-confined Stark effect (QCSE) is an established optical modulation mechanism, yet top-performing modulators harnessing it rely on costly fabrication processes. Here, we present large modulation amplitudes for solution-processed layered hybrid perovskites and a modulation mechanism related to the orientational polarizability of dipolar cations confined within these self-assembled quantum wells. We report an anomalous (blue-shifting) QCSE for layers that contain methylammonium cations, in contrast with cesium-containing layers that show normal (red-shifting) behavior. We attribute the blue-shifts to an extraordinary diminution in the exciton binding energy that arises from an augmented separation of the electron and hole wavefunctions caused by the orientational response of the dipolar cations. The absorption coefficient changes, realized by either the red- or blue-shifts, are the strongest among solution-processed materials at room temperature and are comparable to those exhibited in the highest-performing epitaxial compound semiconductor heterostructures.
57 citations
TL;DR: In this article, the authors used monolayer molybdenum diselenide (MoSe2) as a model system to demonstrate that the driving optical field can couple a hierarchy of excitonic states and the many-body inter-valley biexciton state plays a dominant role in the optical Stark effect.
Abstract: Floquet states, where a periodic optical field coherently drives electrons in solids1–3, can enable novel quantum states of matter4–6. A prominent approach to realize Floquet states is based on the optical Stark effect. Previous studies on the optical Stark effect often treated the excited state in solids as free quasi-particles3,7–12. However, exciton–exciton interactions can be sizeably enhanced in low-dimensional systems and may lead to light–matter interactions that are qualitatively different from those in the non-interacting picture. Here we use monolayer molybdenum diselenide (MoSe2) as a model system to demonstrate that the driving optical field can couple a hierarchy of excitonic states, and the many-body inter-valley biexciton state plays a dominant role in the optical Stark effect. Specifically, the exciton–biexciton coupling in monolayer MoSe2 breaks down the valley selection rules based on the non-interacting exciton picture. The photon-dressed excitonic states exhibit an energy redshift, splitting or blueshift as the driving photon frequency varies below the exciton transition. We determine a binding energy of 21 meV for the inter-valley biexciton and a transition dipole moment of 9.3 debye for the exciton–biexciton transition. Our study reveals the crucial role of many-body effects in coherent light–matter interaction in atomically thin two-dimensional materials. Light–matter interactions in monolayer MoSe2 can be dramatically modified by the interactions between the excitonic states, leading to a rich set of light-driven coherent phenomena.
50 citations
TL;DR: In this article, it was shown that without the dipole self-energy, the so-called depolarization shift is not properly described and that without it, the combined light-matter system is unstable.
Abstract: Most theoretical studies for correlated light-matter systems are performed within the long-wavelength limit, i.e., the electromagnetic field is assumed to be spatially uniform. In this limit the so-called length-gauge transformation for a fully quantized light-matter system gives rise to a dipole self-energy term in the Hamiltonian, i.e., a harmonic potential of the total dipole matter moment. In practice this term is often discarded as it is assumed to be subsumed in the kinetic energy term. In this work we show the necessity of the dipole self-energy term. First and foremost, without it the light-matter system in the long-wavelength limit does not have a ground-state, i.e., the combined light-matter system is unstable. Further, the mixing of matter and photon degrees of freedom due to the length-gauge transformation, which also changes the representation of the translation operator for matter, gives rise to the Maxwell equations in matter and the omittance of the dipole self-energy leads to a violation of these equations. Specifically we show that without the dipole self-energy the so-called 'depolarization shift' is not properly described. Finally we show that this term also arises if we perform the semi-classical limit after the length-gauge transformation. In contrast to the standard approach where the semi-classical limit is performed before the length-gauge transformation, the resulting Hamiltonian is bounded from below and thus supports ground-states. This is very important for practical calculations and for density-functional variational implementations of the non-relativistic QED formalism. For example, the existence of a combined light-matter ground-state allows one to calculate the Stark shift non-perturbatively.
48 citations
TL;DR: The single-molecule limit in electromechanical sensing is realized through TERS-relayed molecular force microscopy through the vibrational spectrum of a single carbon monoxide molecule adsorbed on the tip apex of a scanning tunneling microscope to image electrostatic fields with submolecular spatial resolution.
Abstract: The vibrational spectrum of a single carbon monoxide molecule, adsorbed on the tip apex of a scanning tunneling microscope, is used to image electrostatic fields with submolecular spatial resolution. The method takes advantage of the vibrational Stark effect to image local electrostatic fields and the single-molecule sensitivity of tip-enhanced Raman scattering (TERS) to optically relay the signal. We apply the method to single metalloporphyrins adsorbed on Au(111) to image molecular charges, intramolecular polarization, local photoconductivity, atomically resolved hydrogen bonds, and surface electron density waves.
45 citations
TL;DR: In this article, a transmon qubit was used to measure the energy sensitivity of weak microwave signals in the GHz regime, where the unknown signal frequency and amplitude can be deduced from the higher level ac Stark shift.
Abstract: Analyzing weak microwave signals in the GHz regime is a challenging task if the signal level is very low and the photon energy widely undefined. A superconducting qubit can detect signals in the low photon regime, but due to its discrete level structure, it is only sensitive to photons of certain energies. With a multilevel quantum system (qudit) in contrast, the unknown signal frequency and amplitude can be deduced from the higher level ac Stark shift. The measurement accuracy is given by the signal amplitude, its detuning from the discrete qudit energy level structure, and the anharmonicity. We demonstrate an energy sensitivity in the order of ${10}^{\ensuremath{-}3}$ with a measurement range of more than $1\phantom{\rule{0.28em}{0ex}}\mathrm{GHz}$. Here, using a transmon qubit, we experimentally observe shifts in the transition frequencies involving up to three excited levels. These shifts are in good agreement with an analytic circuit model and master equation simulations. For large detunings, we find the shifts to scale linearly with the power of the applied microwave drive. Exploiting the effect, we demonstrated a power meter which makes it possible to characterize the microwave transmission from source to sample.
44 citations
TL;DR: Recent applications of nitrile VSE probes are highlighted with an emphasis on experiments that have helped shape the understanding of the determinants ofNitrile frequencies in both hydrogen bonding and nonhydrogen bonding environments.
Abstract: Measurement of the electrostatic interactions that give rise to biological functions has been a longstanding challenge in biophysics. Advances in spectroscopic techniques over the past two decades have allowed for the direct measurement of electric fields in a wide variety of biological molecules and systems via the vibrational Stark effect (VSE). The frequency of the nitrile stretching oscillation has received much attention as an electric field reporter because of its sensitivity to electric fields and its occurrence in a relatively transparent region of the infrared spectrum. Despite these advantages and its wide use as a VSE probe, the nitrile stretching frequency is sensitive to hydrogen bonding in a way that complicates the straightforward relationship between measured frequency and environmental electric field. Here we highlight recent applications of nitrile VSE probes with an emphasis on experiments that have helped shape our understanding of the determinants of nitrile frequencies in both hydrogen bonding and nonhydrogen bonding environments.
TL;DR: The Stark effect plays a key role in understanding why, against expectation, alkane thiols are not high-performance molecular rectifiers.
Abstract: Many attempts to obtain high current rectification ratios (RRs) in molecular electronics are triggered by a potentiometer rule argument, which predicts that a strongly asymmetric location of the dominant molecular orbital yields large RR-values. Invoking this argument, molecular junctions based on alkane monothiols (CnT) can be expected to exhibit high RRs; the HOMO of these molecules is localized on the thiol terminal group bonded to one electrode. The extensive current–voltage (I–V) results for CP-AFM (conducting probe atomic force microscope) CnT junctions of various molecular lengths (n = 7, 8, 9, 10, and 12) and different metallic contacts (Ag, Au, and Pt) are consistent with conduction dominated by the HOMO, but the measured RR ∼ 1.5 is much smaller than that predicted by the potentiometer rule framework. Further, the linear shift in the HOMO position with applied bias, γ, which gives rise to rectification, is also smaller than expected, and critically, γ has the opposite sign from potentiometer rule predictions. Companion ab initio OVGF (outer valence Green's function) quantum chemical calculations provide important insight. Namely, a linear Stark shift γm is calculated for the HOMO of CnT molecules for electric field strengths (106–107 V cm−1) typical of molecular junctions, and the sign of γm matches the sign of the experimental γ for junctions derived from transport measurements, suggesting that the Stark effect plays an important role. However, the magnitude of the measured γ is only 10–15% of the computed value γm. We propose that this implies that the contacts are far from optimal; they substantially screen the effect of the applied bias, possibly via molecule–electrode interface states. We predict that, with optimized contacts, the rectification ratios in CnT-based junctions can reach reasonably high values (RR ≈ 500). We believe that Stark shifts and limited current rectification due to non-ideal contacts discussed here for the specific case of alkane monothiol junctions are issues of general interest for molecular electronics that deserve further consideration.
TL;DR: In this article, a detailed profile of the spin-orbit interaction of a silicon metal-oxide-semiconductor double quantum dot system is presented, and the authors exploit the tunability of the derivative of the Stark shift of one of the dots to reduce its sensitivity to electric noise and observe an 80 % increase in $T_2^*$
Abstract: Silicon quantum dots are considered an excellent platform for spin qubits, partly due to their weak spin-orbit interaction. However, the sharp interfaces in the heterostructures induce a small but significant spin-orbit interaction which degrade the performance of the qubits or, when understood and controlled, could be used as a powerful resource. To understand how to control this interaction we build a detailed profile of the spin-orbit interaction of a silicon metal-oxide-semiconductor double quantum dot system. We probe the derivative of the Stark shift, $g$-factor and $g$-factor difference for two single-electron quantum dot qubits as a function of external magnetic field and find that they are dominated by spin-orbit interactions originating from the vector potential, consistent with recent theoretical predictions. Conversely, by populating the double dot with two electrons we probe the mixing of singlet and spin-polarized triplet states during electron tunneling, which we conclude is dominated by momentum-term spin-orbit interactions that varies from 1.85 MHz up to 27.5 MHz depending on the magnetic field orientation. Finally, we exploit the tunability of the derivative of the Stark shift of one of the dots to reduce its sensitivity to electric noise and observe an 80 % increase in $T_2^*$. We conclude that the tuning of the spin-orbit interaction will be crucial for scalable quantum computing in silicon and that the optimal setting will depend on the exact mode of qubit operations used.
TL;DR: SERS is used to measure the vibrational Stark shifts of surface-bound thiolated-benzonitrile molecules bound to an electrode surface during hydrogen evolution reactions (HERs), which results in a highly linear electric field versus applied electrochemical voltage relation.
Abstract: We report the use of surface-enhanced Raman scattering (SERS) to measure the vibrational Stark shifts of surface-bound thiolated-benzonitrile molecules bound to an electrode surface during hydrogen evolution reactions (HERs). Here, the electrode surface consists of Au nanoislands deposited both with and without an underlying layer of monolayer graphene on a glass substrate. The Stark shifts observed in the nitrile (C–N) stretch frequency (around 2225 cm–1) are used to report the local electric field strength at the electrode surface under electrochemical working conditions. Under positive (i.e., oxidative) applied potentials [vs normal hydrogen electrode (NHE)], we observe blue shifts of up to 7.6 cm–1, which correspond to local electric fields of 22 mV/cm. Under negative applied potentials (vs NHE), the C–N stretch frequency is red-shifted by only about 1 cm–1. This corresponds to a regime in which the electrochemical current increases exponentially in the hydrogen evolution process. Under these finite e...
TL;DR: AyAyuso et al. as mentioned in this paper presented a comprehensive analytical model that can describe the most relevant features arising in the high-order harmonic spectra of chiral molecules driven by strong bi-elliptical fields.
Abstract: The generation of high-order harmonics in a medium of chiral molecules driven by intense bi-elliptical laser fields can lead to strong chiroptical response in a broad range of harmonic numbers and ellipticities [D. Ayuso et al, J. Phys. B 51, 06LT01 (2018)]. Here we present a comprehensive analytical model that can describe the most relevant features arising in the high-order harmonic spectra of chiral molecules driven by strong bi-elliptical fields. Our model recovers the physical picture underlying chiral high-order harmonic generation based on ultrafast chiral hole motion and identifies the rotationally invariant molecular pseudoscalars responsible for chiral dynamics. Using the chiral molecule propylene oxide as an example, we show that one can control and enhance the chiral response in bi-elliptical high-order harmonic generation by tailoring the driving field, in particular by tuning its frequency, intensity and ellipticity, exploiting a suppression mechanism of achiral background based on the linear Stark effect.
TL;DR: In this paper, the Stark shift of the hyperfine states of polar molecules embedded in a solid rare-gas matrix was found to depend on the molecular orientation, which may significantly improve the measurements of the electron electric dipole moment.
Abstract: The Stark shift of the hyperfine states of polar molecules embedded in a solid rare-gas matrix is found to depend on the molecular orientation. This finding may significantly improve the measurements of the electron electric dipole moment by using large ensembles of polar molecules trapped in rare-gas matrices with orientation-dependent detections.
TL;DR: In this paper, the nanosecond repetitively pulsed discharge to the micrometer scale, in a 200 µm discharge gap in air at atmospheric pressure and room temperature, focusing on measurements of the electron number density and electron temperature, was confined.
Abstract: We confine the nanosecond repetitively pulsed discharge to the micrometer scale, in a 200 µm discharge gap in air at atmospheric pressure and room temperature, focusing on measurements of the electron number density and electron temperature. The Stark broadening of H, O and N atomic lines and electrical conductivity both show that the electron number density reaches a maximum value of 1 × 1019 cm−3. Boltzmann plots show the electron temperature to be 72 kK several nanoseconds after the end of the pulse of applied electric field. We will use these results to determine the mechanism responsible for electron loss during the early recombination phase (t < 500 ns) and comment on the degree of ionization and dissociation.
TL;DR: This work shows that at the scanning tunneling microscope junction of a CO-terminated Ag tip, the large bias dependence of the CO frequency shift is due to ground-state charge transfer from the Ag tip into the CO π* orbital softening the C-O bond at more positive biases.
Abstract: Tip-enhanced Raman spectromicroscopy (TERS) with CO-terminated plasmonic tips can probe angstrom-scale features of molecules on surfaces. The development of this technique requires understanding of how chemical environments affect the CO vibrational frequency and TERS intensity. At the scanning tunneling microscope junction of a CO-terminated Ag tip, we show that rather than the classical vibrational Stark effect, the large bias dependence of the CO frequency shift is due to ground-state charge transfer from the Ag tip into the CO π* orbital softening the C–O bond at more positive biases. The associated increase in Raman intensity is attributed to a bias-dependent chemical enhancement effect, where a positive bias tunes a charge-transfer excited state close to resonance with the Ag plasmon. This change in Raman intensity is contrary to what would be expected based on changes in the tilt angle of the CO molecule with bias, demonstrating that the Raman intensity is dominated by electronic rather than geomet...
TL;DR: This paper performed extensive simulation on the momentum pattern of hydrogen ionized by two time-delayed oppositely circularly polarized attosecond pulses and deciphered that this distortion is originated from the temporal characteristics of the dynamic Stark phase which is nonlinear in time.
Abstract: In this paper, we report our numerical simulation on the symmetry distortion and mechanism of the vortex-shaped momentum distribution of hydrogen atom by taking into account of the dynamic Stark effect. By deploying the strong field approximation (SFA) theory, we performed extensive simulation on the momentum pattern of hydrogen ionized by two time-delayed oppositely circularly polarized attosecond pulses. We deciphered that this distortion is originated from the temporal characteristics of the dynamic Stark phase which is nonlinear in time.
TL;DR: In this paper, the electronic structure and properties of monolayer GaSe in a transverse electric field were investigated for applications in optoelectronics and spintronics, and the authors provided guidelines for exploiting GaSe properties in various realms of device physics.
Abstract: Fully electrical control of devices is keenly pursued for applications in optoelectronics and spintronics. Inspired by the continual discovery of interesting features in two-dimensional semiconductors, the authors investigate the electronic structure and properties of monolayer GaSe in a transverse electric field. Density functional theory predicts a giant Stark effect, switchable optical anisotropy, and controllable spin-orbit coupling and spin polarization in this group-IIIA monochalcogenide. This study provides welcome guidelines for exploiting GaSe in various realms of device physics.
TL;DR: In this article, the effect of an external in-plane electric field on neutral and charged exciton states in two-dimensional (2D) materials is theoretically investigated, and it is shown that trions in the anisotropic case of monolayer phosphorene are especially robust under electric fields, so that fields as high as 100 kV/cm yield no significant effect on the trion binding energy or probability density distribution.
Abstract: The effect of an external in-plane electric field on neutral and charged exciton states in two-dimensional (2D) materials is theoretically investigated. These states are argued to be strongly bound, so that electron-hole dissociation is not observed up to high electric field intensities. Trions in the anisotropic case of monolayer phosphorene are demonstrated to be especially robust under electric fields, so that fields as high as 100 kV/cm yield no significant effect on the trion binding energy or probability density distribution. Polarizabilities of excitons are obtained from the parabolicity of numerically calculated Stark shifts. For trions, a fourth order Stark shift is observed, which enables the experimental verification of hyperpolarizability in 2D materials, as observed in the highly excited states of the Rydberg series of atoms and ions.
TL;DR: This work aims at elucidating the long-range modulation of electric fields in proteins upon binding to charged surfaces, based on cytochrome c variants carrying nitrile reporters for the vibrational Stark effect that are incorporated into the protein via genetic engineering and chemical modification.
Abstract: Electrostatic interactions are essential for controlling the protein structure and function. Whereas so far experimental and theoretical efforts focused on the effect of local electrostatics, this work aims at elucidating the long-range modulation of electric fields in proteins upon binding to charged surfaces. The study is based on cytochrome c (Cytc) variants carrying nitrile reporters for the vibrational Stark effect that are incorporated into the protein via genetic engineering and chemical modification. The Cytc variants were thoroughly characterized with respect to possible structural perturbations due to labeling. For the proteins in solution, the relative hydrogen bond occupancy and the calculated electric fields, both obtained from molecular dynamics (MD) simulations, and the experimental nitrile stretching frequencies were used to develop a relationship for separating hydrogen-bonding and non-hydrogen-bonding electric field effects. This relationship provides an excellent description for the stable Cytc variants in solution. For the proteins bound to Au electrodes coated with charged self-assembled monolayers (SAMs), the underlying MD simulations can only account for the electric field changes Δ Eads due to the formation of the electrostatic SAM-Cytc complexes but not for the additional contribution, Δ Eint, representing the consequences of the potential drops over the electrode/SAM/protein interfaces. Both Δ Eads and Δ Eint, determined at distances between 20 and 30 A with respect to the SAM surface, are comparable in magnitude to the non-hydrogen-bonding electric field in the unbound protein. This long-range modulation of the internal electric field may be of functional relevance for proteins in complexes with partner proteins (Δ Eads) and attached to membranes (Δ Eads + Δ Eint).
TL;DR: In this paper, it was shown that Kerr rotation is a sensitive probe of valley-dependent energy splitting induced by the optical Stark effect in two-dimensional semiconductors, allowing detection of shifts as small as 4 \ensuremath{\mu}eV -the lowest reported value.
Abstract: The authors show here that Kerr rotation is a sensitive probe of valley-dependent energy splitting induced by the optical Stark effect in two-dimensional semiconductors. Kerr rotation rejects the polarization-independent background and probes a complementary dielectric response from established absorption-based techniques, allowing detection of shifts as small as 4 \ensuremath{\mu}eV - the lowest reported value so far. The authors apply this improved valley Stark spectroscopy to a wider range of materials by observing Stark shifts of two energetically distinct exciton species in MoS${}_{2}$, representing the first valley- and energy-selective Stark effect in a single material.
TL;DR: In this article, the analytical characteristics of U isotopic analysis with laser-induced breakdown spectroscopy (LIBS) were investigated by analyzing a series of U3O8-Li2B4O7 fused glassy disks.
07 Aug 2018
TL;DR: In this article, a method to apply dc electric fields within a superconducting waveguide cavity, which is based on the insertion of dc electrodes at the nodes of the microwave electric field, is presented.
Abstract: Three-dimensional microwave waveguide cavities are essential tools for many cavity quantum electrodynamics experiments. However, the need to control quantum emitters with dc magnetic fields inside the cavity often limits such experiments to normal-conducting cavities with relatively low quality factors of about 104. Similarly, controlling quantum emitters with dc electric fields in normal- and superconducting waveguide cavities has so far been difficult, because the insertion of dc electrodes has strongly limited the quality factor. Here, we present a method to apply dc electric fields within a superconducting waveguide cavity, which is based on the insertion of dc electrodes at the nodes of the microwave electric field. Moreover, we present a method to apply dc magnetic fields within the same cavity by trapping the magnetic flux in holes positioned in facing walls of the cavity. We demonstrate that the TE301 mode of such a superconducting, rectangular cavity made from niobium maintains a high internal quality factor of at the few photon level and a base temperature of 3 K. A cloud of Rydberg atoms coupled to the microwave electric field of the cavity is used to probe the applied dc electric and magnetic fields via the quadratic Stark effect and the Zeeman effect, respectively.
TL;DR: In this paper, the influence of external magnetic field on the laser-induced breakdown spectroscopy of laser induced plasma as a function of pressures has been examined Aluminum samples are analyzed by using Nd:YAG (1064nm, 8 ns) under helium and argon gases at pressure ranging from 1 to 80
TL;DR: In this article, a review of studies of the electric field influence on spectral lines is presented, beginning from the discovery of the Stark effect, and in particular focused on phenomena related to the effects of the plasma microfield non-uniformity.
Abstract: A review of studies of the electric-field influence on spectral lines is presented, beginning from the discovery of the Stark effect, and in particular focused on phenomena related to the effects of the plasma microfield non-uniformity.
TL;DR: In this article, the authors study the variation of electronic properties for armchair-edge phosphorene nanoribbons (APNRs) modulated by a transverse electric field.
TL;DR: The off-resonant AC Stark shift for coherent population trapping (CPT) resonances probed with Ramsey spectroscopy is investigated experimentally and theoretically in this article.
Abstract: The off-resonant AC Stark shift for coherent population trapping (CPT) resonances probed with Ramsey spectroscopy is investigated experimentally and theoretically. Measurements with laser-cooled $^{87}$Rb atoms show excellent quantitative agreement with a simple theory. The shift depends on the relative intensity of the two CPT light fields, but depends only weakly on the total intensity. Since the origin of the shift is through couplings of the interrogation light to off-resonant excited state hyperfine levels, the size and sign of the shift depend on the specific interrogation scheme. However, the simple theory shows that for several commonly used interrogation schemes the off-resonant shift goes to zero at specific values of this relative intensity.
Journal Article•
TL;DR: In this article, it was shown that Kerr rotation is a sensitive probe of valley-dependent energy splitting induced by the optical Stark effect in two-dimensional semiconductors, allowing detection of shifts as small as 4 \ensuremath{\mu}eV -the lowest reported value.
Abstract: The authors show here that Kerr rotation is a sensitive probe of valley-dependent energy splitting induced by the optical Stark effect in two-dimensional semiconductors. Kerr rotation rejects the polarization-independent background and probes a complementary dielectric response from established absorption-based techniques, allowing detection of shifts as small as 4 \ensuremath{\mu}eV - the lowest reported value so far. The authors apply this improved valley Stark spectroscopy to a wider range of materials by observing Stark shifts of two energetically distinct exciton species in MoS${}_{2}$, representing the first valley- and energy-selective Stark effect in a single material.