Publications

Order by: publication date number of citations

• Dynamical spin-orbit-based spin transistor

  Fahriye N. Gürsoy, P. Reck, C. Gorini, K. Richter, I. Adagideli

  SciPost Phys. 14, 060 (2023) · published 4 April 2023 | Toggle abstract · pdf

  Spin-orbit interaction (SOI) has been a key tool to steer and manipulate spin-dependent transport properties in two-dimensional electron gases. Here we demonstrate how spin currents can be created and efficiently read out in nano- or mesoscale conductors with time-dependent and spatially inhomogeneous Rashba SOI. Invoking an underlying non-Abelian SU(2) gauge structure we show how time-periodic spin-orbit fields give rise to spin electric forces and enable the generation of pure spin currents of the order of several hundred nano-Amperes. In a complementary way, by combining gauge transformations with "hidden" Onsager relations, we exploit spatially inhomogeneous Rashba SOI to convert spin currents (back) into charge currents. In combining both concepts, we devise a spin transistor that integrates efficient spin current generation, by employing dynamical SOI, with its experimentally feasible detection via conversion into charge signals. We derive general expressions for the respective spin- and charge conductance, covering large parameter regimes of SOI strength and driving frequencies, far beyond usual adiabatic approaches such as the frozen scattering matrix approximation. We check our analytical expressions and approximations with full numerical spin-dependent transport simulations and demonstrate that the predictions hold true in a wide range from low to high driving frequencies.

• Temporal fluctuations of correlators in integrable and chaotic quantum systems

  Talía L. M. Lezama, Yevgeny Bar Lev, Lea F. Santos

  SciPost Phys. 15, 244 (2023) · published 18 December 2023 | Toggle abstract · pdf

  We provide bounds on temporal fluctuations around the infinite-time average of out-of-time-ordered and time-ordered correlators of many-body quantum systems without energy gap degeneracies. For physical initial states, our bounds predict the exponential decay of the temporal fluctuations as a function of the system size. We numerically verify this prediction for chaotic and interacting integrable spin-1/2 chains, which satisfy the assumption of our bounds. On the other hand, we show analytically and numerically that for the XX model, which is a noninteracting system with gap degeneracies, the temporal fluctuations decay polynomially with system size for operators that are local in the fermion representation and decrease exponentially in the system size for non-local operators. Our results demonstrate that the decay of the long-time temporal fluctuations of correlators cannot be used as a reliable metric of chaos or lack thereof.

• Direct measurements of cosmic rays with the calorimetric electron telescope on the international space station

  Y. Akaike, O. Adriani, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W. R. Binns, M. Bongi, P. Brogi, A. Bruno, J. H. Buckley, N. Cannady, G. Castellini, C. Checchia, M. L. Cherry, G. Collazuol, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T. G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M. H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H. S. Krawczynski, J. F. Krizmanic, P. Maestro, P. S. Marrocchesi, A. M. Messineo, J. W. Mitchell, S. Miyake, A. A. Moiseev, M. Mori, N. Mori, H. M. Motz, K. Munakata, S. Nakahira, J. Nishimura, G. A. de Nolfo, S. Okuno, J. F. Ormes, S. Ozawa, L. Pacini, P. Papini, B. F. Rauch, S. B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J. P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, W. V. Zober

  SciPost Phys. Proc. 13, 040 (2023) · published 29 September 2023 | Toggle abstract · pdf

  The CALorimetric Electron Telescope, CALET, has been measuring high-energy cosmic rays on the International Space Station since October 13, 2015. The scientific objectives addressed by the mission are to search for possible nearby sources of high-energy electrons and potential signatures of dark matter, and to investigate the details of galactic cosmic-ray acceleration and propagation. The calorimetric instrument, which is 30 radiation lengths or 1.3 proton interaction lengths thick with fine imaging capability, is optimized to measure cosmic-ray electrons by achieving large proton rejection and excellent energy resolution well into the TeV region. In addition, very wide dynamic range of energy measurement and individual charge identification capability enable us to measure proton and nuclei spectra from a few tens GeV to a PeV scale. Nearly 20 million cosmic-ray shower events over 10 GeV per month are triggered and the continuous observation has been kept without any major interruption since the start of operation. Using the data obtained over 6.5 years of operation, we will present a brief summary of the CALET observation including electron spectrum, and proton and nuclei spectra as well as the performance study on orbit with MC simulations.

• Mesoscopic electron transport and atomic gases, a review of Frank W. J. Hekking's scientific work

  Luigi Amico, Denis M. Basko, F Sebastián Bergeret, Olivier Buisson, Hervé Courtois, Rosario Fazio, Wiebke Guichard, Anna Minguzzi, Jukka Pekola, Gerd Schön

  SciPost Phys. 5, 009 (2018) · published 27 July 2018 | Toggle abstract · pdf

  Frank W. J. Hekking performed his PhD work on "Aspects of Electron Transport in Semiconductor Nanostructures" at the TU Delft in 1992. He then worked as a postdoc at the University of Karlsruhe, the University of Minnesota, the Cavendish Laboratory at the University of Cambridge, and the Ruhr University at Bochum. In 1999 he joined the LPMMC (Laboratoire de Physique et Mod\' elisation des Milieux Condens\' es) in Grenoble and was appointed Professor at the Universit\' e Joseph Fourier and afterwards Universit\' e Grenoble Alpes. Frank Hekking was nominated as a member of the Institut Universitaire de France, for the periods 2002-2007 and 2012-2017. This review provides an overview of his scientific contributions to several fields of mesoscopic electron transport and superconductivity as well as atomic gases, and is organized along sections describing the different themes.

• Measurements of the Antiquark Flavor Asymmetry in the Proton by the Drell-Yan Experiment SeaQuest

  Kei Nagai

  SciPost Phys. Proc. 8, 119 (2022) · published 13 July 2022 | Toggle abstract · pdf

  The antiquark flavor asymmetry dbar/ubar in the proton gives an insight on the non-perturbative structure of the proton. The SeaQuest experiment measured the Drell–Yan cross section ratio of proton-deuterium to proton-proton to determine the antiquark flavor asymmetry dbar/ubar precisely in the range of 0.13<x<0.45. SeaQuest provides the evidence of dbar/ubar > 1.0 over a wide range of momenta. Some theoretical models reproduce this result.

• Approaching the first any light particle search II science run

  Aaron D. Spector for the ALPS Collaboration

  SciPost Phys. Proc. 12, 039 (2023) · published 4 July 2023 | Toggle abstract · pdf

  The Any Light Particle Search II (ALPS II) is a light-shining-through-a-wall (LSW) experiment based at DESY in Hamburg, Germany, that will search for axions and axion-like particles down to the coupling of the axion to two photons of $g_{a\gamma\gamma}$ >2$\times10^{-11}$ GeV$^{-1}$ for masses below 0.1 meV. ALPS II will use two strings of superconducting dipole magnets that are over one hundred meters in length, as well as optical cavities before and after the wall to boost the effective signal rate of the regenerated photons by more than 12 orders of magnitude when compared to previous generations of LSW experiments. Data taking with a simplified optical system is expected to begin in early 2023.

• Application of Lorentzian CFT Principal Series Representation to Near Forward Scattering

  Pulkit Agarwal, Richard C. Brower, Timothy G. Raben, Chung-I Tan

  SciPost Phys. Proc. 10, 026 (2022) · published 11 August 2022 | Toggle abstract · pdf

  We present a discussion on recent progress in high energy diffraction from the perspective of AdS/CFT, through which a unified treatment for both perturbative and nonperturbative Pomeron emerges. By working with Unitary Irreducible Representation of Conformal group, a frame is provided in extending AdS/CFT to both forward and nearforward scattering. We present an analysis involving an exact solution to conformal blocks in Minkowski CFT and discuss possible applications. Phenomenological applications can range from forward scattering to DIS/DVCS/TMD at LHC energies and beyond.

• Monopoles in Dirac spin liquids and their symmetries from instanton calculus

  Shankar Ganesh, Joseph Maciejko

  SciPost Phys. 16, 118 (2024) · published 2 May 2024 | Toggle abstract · pdf

  The Dirac spin liquid (DSL) is a two-dimensional (2D) fractionalized Mott insulator featuring massless Dirac spinon excitations coupled to a compact U(1) gauge field, which allows for flux-tunneling instanton events described by magnetic monopoles in (2+1)D Euclidean spacetime. The state-operator correspondence of conformal field theory has been used recently to define associated monopole operators and determine their quantum numbers, which encode the microscopic symmetries of conventional ordered phases proximate to the DSL. In this work, we utilize semiclassical instanton methods not relying on conformal invariance to construct monopole operators directly in (2+1)D spacetime as instanton-induced 't Hooft vertices, i.e., fermion-number-violating effective interactions originating from zero modes of the Euclidean Dirac operator in an instanton background. In the presence of a flavor-adjoint fermion mass, resummation of the instanton gas is shown to select the correct monopole to be proliferated, in accordance with predictions of the state-operator correspondence. We also show that our instanton-based approach is able to determine monopole quantum numbers on bipartite lattices.

• Efficient qudit based scheme for photonic quantum computing

  Márton Karácsony, László Oroszlány, Zoltan Zimboras

  SciPost Phys. Core 7, 032 (2024) · published 3 June 2024 | Toggle abstract · pdf

  Linear optics is a promising alternative for the realization of quantum computation protocols due to the recent advancements in integrated photonic technology. In this context, usually qubit based quantum circuits are considered, however, photonic systems naturally allow also for d-ary, i.e., qudit based, algorithms. This work investigates qudits defined by the possible photon number states of a single photon in d > 2 optical modes. We demonstrate how to construct locally optimal non-deterministic many-qudit gates using linear optics and photon number resolving detectors, and explore the use of qudit cluster states in the context of a d-ary optimization problem. We find that the qudit cluster states require less optical modes and are encoded by a fewer number of entangled photons than the qubit cluster states with similar computational capabilities. We illustrate the benefit of our qudit scheme by applying it to the k-coloring problem.

• Identifying diffusive length scales in one-dimensional Bose gases

  Frederik Møller, Federica Cataldini, Jörg Schmiedmayer

  SciPost Phys. Core 7, 025 (2024) · published 7 May 2024 | Toggle abstract · pdf

  In the hydrodynamics of integrable models, diffusion is a subleading correction to ballistic propagation. Here we quantify the diffusive contribution for one-dimensional Bose gases and find it most influential in the crossover between the main thermodynamic regimes of the gas. Analysing the experimentally measured dynamics of a single density mode, we find diffusion to be relevant only for high wavelength excitations. Instead, the observed relaxation is solely caused by a ballistically driven dephasing process, whose time scale is related to the phonon lifetime of the system and is thus useful to evaluate the applicability of the phonon bases typically used in quantum field simulators.