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• The early Riksbank played an important role in providing emergency finance for Sweden. • I find that political and legal restrictions on the Riksbank were at least a proximate cause of Sweden's military defeats. • Policy experimentation at the Riksbank led to inflation and corresponding reductions in economic activity. At the beginning of the 18th century, Sweden was an imperial power that had just sustained a century of modest economic growth. In 1800, Sweden's empire was gone, after a series of military defeats. Real GDP per capita had fallen to the same level as the early 1600s. In other words, the 18th century witnessed the end of the Swedish Empire and a startling reversal of economic progress. In this paper, I propose a possible explanation for both of these outcomes. First, I argue that Sweden's limited fiscal capacity played an important role. The creation of the Riksbank should have facilitated government borrowing and military spending as the Bank of England did for the British. However, the Riksbank was not designed or equipped for this role. I document the constraints on financing national defense through the Riksbank and argue that the bank was ill-equipped to finance an adequate national defense. This explains the reversal of the empire. Second, when the Hats took power in the Riksdag in 1739, they used the Riksbank to give loans to firms, which were financed through the issuance of bank notes. The objective was to increase investment and economic activity. I find no evidence that these loans had any effect on real GDP per capita. However, the resulting inflation has a negative and significant effect on output during the period of inconvertible paper money. The combined evidence suggests that Hat policy contributed to the decline in economic activity during the reversal of fortune. [ABSTRACT FROM AUTHOR]

We employ a monetary model with endogenous search and random consumption preferences to consider the extent to which a government can ban an alternative currency, like bitcoin. We define a ban as a policy whereby government agents refuse to accept an alternative currency and mete out punishments to private agents caught using it. After identifying monetary equilibria where an alternative currency is accepted, we then derive the conditions under which a ban might deter its use. As in earlier studies, we show that a government of sufficient size can prevent an alternative currency from circulating without relying on punishments. We also show that, given its size, a government can ban an alternative currency so long as it is willing and able to mete out sufficiently severe punishments. [ABSTRACT FROM AUTHOR]

The recent proliferation of bitcoin has been a boon for users but might pose problems for governments. Indeed, some governments have already taken steps to ban or discourage the use of bitcoin. In a model with endogenous matching and random consumption preferences, we find multiple monetary equilibria including one in which bitcoin coexists with official currency. We then identify the conditions under which government transactions policy might deter the use of bitcoin. We show that such a policy becomes more difficult if some users strictly prefer bitcoin because they can avoid other users holding the official currency in the matching process. ( JEL C78, E41, E42, E50) [ABSTRACT FROM AUTHOR]

The article discusses the banking concepts of contingent liability, capital requirements, and their relation to banking and financial reform. It discusses the double liability system in the U.S., bank insolvency, and the marketability and tradability of shares. The author argues that a contingent liability system is preferable to limited liability and that sensible banking reform would incorporate a realignment of bank incentives instead of solely establishing higher capital requirements.

The generation of rapidly tunable optical vortex (OV) beams is one of the most demanding research areas of the present era as they possess orbital angular momentum (OAM) with additional degrees of freedom that can be exploited to enhance signal‐carrying capacity by using mode division multiplexing and information encoding in optical communication. Particularly, rapidly tunable OAM devices at a fixed wavelength in the telecom band stir extensive interest among researchers for both classical and quantum applications. This article demonstrates the realistic design of a Si‐integrated photonic device for rapidly tunable OAM wave generation at a 1550‐nm wavelength by using an ultra‐low‐loss phase change material (PCM) embedded with a Si‐ring resonator with angular gratings. Different OAM modes are achieved by tuning the effective refractive index using rapid electrical switching of Sb2Se3 film from amorphous to crystalline states and vice versa. The generation of OAM waves relies on a traveling wave modulation of the refractive index of the micro‐ring, which breaks the degeneracy of oppositely oriented whispering gallery modes. The proposed device is capable of producing rapidly tunable OV beams, carrying different OAM modes by using electrically controllable switching of ultra‐low‐loss PCM Sb2Se3. [ABSTRACT FROM AUTHOR]

Programmable and reconfigurable photonics is revolutionized the next generation of Si/SiN‐based photonics processors, optical signal processing, and neural and quantum networks. Ultra‐low loss phase‐change technology has the enormous potential to offer energy‐efficient, extra large‐scale integrated (ELSI) nonvolatile programmable photonics that can overcome the limitations of commonly used volatile and energy‐hungry programmable photonic systems. So far, most of the phase change materials (PCM) devices have already shown to be suitable for programmable and reconfigurable photonic circuit applications that do not require extreme endurance or ultra‐fast switching speeds. However, applications with ultra‐fast speed and multi‐million cycling requirements, such as memory cells, quantum computing, optical displays, and optical modulators necessitate enormous improvements in the existing cycling speed and endurance of PCMs, for high‐performance device configuration. Here, optical switching of an ultra‐low loss PCM (Sb2Se3) is demonstrated with an unprecedented combination of rapid cycling speed (0.6 × 105 cycles s−1) and extreme endurance (> 2 × 106 cycles) that pave the way for ultrafast, large‐scale, programmable, and reconfigurable integrated photonic circuits and devices. [ABSTRACT FROM AUTHOR]

Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 μm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmon theoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the baseline predicted by diffraction theory, are observed in each of the samples at wavelengths that correspond to the excitation of surface plasmon modes. [ABSTRACT FROM AUTHOR]

Experimental results pertaining to plasmon resonance tunneling through a highly conductive zinc oxide (ZnO) layer with subwavelength hole-arrays is investigated in the mid-infrared regime. Gallium-doped ZnO layers are pulsed-laser deposited on a silicon wafer. The ZnO has metallic optical properties with a bulk plasma frequency of 214 THz, which is equivalent to a free space wavelength of 1.4 lm. Hole arrays with different periods and hole shapes are fabricated via a standard photolithography process. Resonant mode tunneling characteristics are experimentally studied for different incident angles and compared with surface plasmon theoretical calculations and finite-difference time-domain simulations. Transmission peaks, higher than the baseline predicted by diffraction theory, are observed in each of the samples at wavelengths that correspond to the excitation of surface plasmon modes. [ABSTRACT FROM AUTHOR]

Recently, single photons have been observed emanating from point defects in two-dimensional (2D) materials including WSe2, WS2, hexagonal-BN, and GaSe, with their energy residing in the direct electronic bandgap. Here, we report single photon emission from a nominal weakly emitting indirect bandgap 2D material through deterministic strain induced localization. A method is demonstrated to create highly spatially localized and spectrally well-separated defect emission sites in the 750–800 nm regime in a continuous epitaxial film of few-layer WSe2 synthesized by a multistep diffusion-mediated gas source chemical vapor deposition technique. To separate the effects of mechanical strain from the substrate or dielectric-environment induced changes in the electronic structure, we created arrays of large isotropically etched ultrasharp silicon dioxide tips with spatial dimensions on the order of 10 μm. We use bending based on the small radius of these tips—on the order of 4 nm—to impart electronic localization effects through morphology alone, as the WSe2 film experiences a uniform SiO2 dielectric environment in the device geometry chosen for this investigation. When the continuous WSe2 film was transferred onto an array of SiO2 tips, an ∼87% yield of localized emission sites on the tips was observed. The outcomes of this report provide fundamental guidelines for the integration of beyond-lab-scale quantum materials into photonic device architectures for all-optical quantum information applications. [ABSTRACT FROM AUTHOR]

A synthetic challenge in faceted metal oxide nanocrystals (NCs) is realizing tunable localized surface plasmon resonance (LSPR) near-field response in the infrared (IR). Cube-shaped nanoparticles of noble metals exhibit LSPR spectral tunability limited to visible spectral range. Here, we describe the colloidal synthesis of fluorine, tin codoped indium oxide (F,Sn:In2O3) NC cubes with tunable IR range LSPR for around 10 nm particle sizes. Free carrier concentration is tuned through controlled Sn dopant incorporation, where Sn is an aliovalent n-type dopant in the In2O3 lattice. F shapes the NC morphology into cubes by functioning as a surfactant on the {100} crystallographic facets. Cube shaped F,Sn:In2O3 NCs exhibit narrow, shape-dependent multimodal LSPR due to corner, edge, and face centered modes. Monolayer NC arrays are fabricated through a liquid-air interface assembly, further demonstrating tunable LSPR response as NC film nanocavities that can heighten near-field enhancement (NFE). The tunable F,Sn:In2O3 NC near-field is coupled with PbS quantum dots, via the Purcell effect. The detuning frequency between the nanocavity and exciton is varied, resulting in IR near-field dependent enhanced exciton lifetime decay. LSPR near-field tunability is directly visualized through IR range scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS). STEM-EELS mapping of the spatially confined near-field in the F,Sn:In2O3 NC array interparticle gap demonstrates elevated NFE tunability in the arrays. [ABSTRACT FROM AUTHOR]

Metamaterials and metasurfaces operating in the visible and near‐infrared (NIR) offer a promising route towards next‐generation photodetectors and devices for solar energy harvesting. While numerous metamaterials and metasurfaces using metals and semiconductors have been demonstrated, semimetals‐based metasurfaces in the vis‐NIR range are notably missing. This work experimentally demonstrates a broadband metasurface superabsorber based on large area, semimetallic, van der Waals platinum diselenide (PtSe2) thin films in agreement with electromagnetic simulations. The results show that PtSe2 is an ultrathin and scalable semimetal that concurrently possesses high index and high extinction across the vis‐NIR range. Consequently, the thin‐film PtSe2 on a reflector separated by a dielectric spacer can absorb >85% for the unpatterned case and ≈97% for the optimized 2D metasurface in the 400–900 nm range making it one of the strongest and thinnest broadband perfect absorbers to date. The results present a scalable approach to photodetection and solar energy harvesting, demonstrating the practical utility of high index, high extinction semimetals for nanoscale optics. [ABSTRACT FROM AUTHOR]

We experimentally probe the multilevel response of GeTe, Ge2Sb2Te5 (GST), and 4% tungsten-doped GST (W-GST) phase change materials (PCMs) using two wavelengths of light: 1550 nm, which is useful for telecom-applications, and near-infrared 780 nm, which is a standard wavelength for many experiments in atomic and molecular physics. We find that the materials behave differently with the excitation at the different wavelengths and identify useful applications for each material and wavelength. We discuss thickness variation in the thin films used as well and comment on the interaction of the interface between the material and the substrate with regard to the multilevel behavior. Due to the differences in penetration depths, absorption, and index contrast, different PCMs could be more suitably used depending on the application and wavelength of operation. [ABSTRACT FROM AUTHOR]

We report an investigation of a planar GeSn p–i–n diode for a high-detectivity photodetector based on an undoped GeSn film. By fabricating n- and p-type regions on the plane of the GeSn film using the complementary metal–oxide–semiconductor technology of ion implantation, a low dark current density is revealed and attributed to the low defect density of the film and current flow suppression around the diode periphery. This yields a specific 1550-nm detectivity of ∼1010 cm Hz1/2 W−1, an order of magnitude higher than that of conventional vertical GeSn-based diodes and comparable to that of commercially available Ge-based diodes. This work provides an alternative approach for achieving a high-detectivity GeSn photodetector that may facilitate its potential applications. [ABSTRACT FROM AUTHOR]

The large impedance mismatch between the highly resistive amorphous state and the highly conductive crystalline state of Ge 2 Sb 2 Te 5 is an impediment for the realization of high-speed electrically switched optical devices. In this paper, we demonstrate that tungsten doping can reduce this resistivity contrast and also results in a lower amorphous state resistivity. Additionally, it lowers the contact resistance, improves the optical contrast, and extends the face-centered-cubic state up to 35 0 ° C , with a minimal impact on thermal conductivity. [ABSTRACT FROM AUTHOR]

High-speed electrical switching of Ge2Sb2Te5 (GST) remains a challenging task due to the large impedance mismatch between the low-conductivity amorphous state and the high-conductivity crystalline state. In this letter, we demonstrate an effective doping scheme using nickel to reduce the resistivity contrast between the amorphous and crystalline states by nearly three orders of magnitude. Most importantly, our results show that doping produces the desired electrical performance without adversely affecting the film's optical properties. The nickel doping level is approximately 2% and the lattice structure remains nearly unchanged when compared with undoped-GST. The refractive indices in amorphous and crystalline states were obtained using ellipsometry which echoes the results of X-ray diffraction. The material's thermal transport properties are measured using time-domain thermoreflectance, showing no change upon doping. The advantages of this doping system will open up opportunities for designing electrically reconfigurable high speed optical elements in the near-infrared spectrum. [ABSTRACT FROM AUTHOR]

Single defects in monolayer WSe2 have been shown to be a new class of single photon emitters and have potential applications in quantum technologies. Whereas previous work relied on optical excitation of single defects in isolated WSe2 monolayers, in this work we demonstrate electrically driven single defect light emission by using both vertical and lateral van der Waals heterostructure devices. In both device geometries, we use few layer graphene as the source and drain and hexagonal boron nitride as the dielectric spacer layers for engineered tunneling contacts. In addition, the lateral devices utilize a split back gate design to realize an electrostatically defined p-i-n junction. At low current densities and low temperatures (~5 K), we observe narrow spectral lines in the electroluminescence (EL) whose properties are consistent with optically excited defect bound excitons. We show that the emission originates from spatially localized regions of the sample, and the EL spectrum from single defects has a doublet with the characteristic exchange splitting and linearly polarized selection rules. All are consistent with previously reported single photon-emitters in optical measurements. Our results pave the way for on-chip and electrically driven single photon sources in two-dimensional semiconductors for quantum technology applications. [ABSTRACT FROM AUTHOR]

We study, by numerical simulations and experimentally, the resonant diffraction by metal (Ag) gratings in the mid-IR ( \sim 10~\mu \textm ) spectral range. The excitation of surface plasmon-polaritons facilitates narrow-band resonantly enhanced diffraction into symmetry-prohibited diffraction orders. We show that, even though the propagation losses for plasmonic modes are greatly reduced at longer wavelengths, the magnitude of the resonant diffraction peak remains limited due to diffraction into other, normally allowed, diffraction orders. The grating depth dependence of the resonant diffraction spectra indicates that with shallower gratings, the Q -factor of the resonance may become as large as 10^{3} – 10^{4}$ , while the magnitude of the peak is reduced. [ABSTRACT FROM AUTHOR]

We report the electroluminescence of a planar p-i-n diode based on an undoped GeSn layer where the p- and n-type electrodes are fabricated by using the CMOS process of ion implantation. The measurement shows a broad spectrum at a peak energy located below the bulk bandgap of Ge associated with indirect optical transition analyzed by taking into account composition- and strain-dependent modeling. This work provides an alternative approach to the fabrication of GeSn-based p-i-n light-emitting diodes as well as moving towards the integration with waveguided on-chip group IV photonic devices. [ABSTRACT FROM AUTHOR]

We report an investigation on the photo-response from a GeSn-based photodetector using a tunable laser with a range of incident light power. An exponential increase in photocurrent and an exponential decay of responsivity with increase in incident optical power intensity were observed at higher optical power range. Time-resolved measurement provided evidence that indicated monomolecular and bimolecular recombination mechanisms for the photo-generated carriers for different incident optical power intensities. This investigation establishes the appropriate range of optical power intensity for GeSn-based photodetector operation. [ABSTRACT FROM AUTHOR]