[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

The last decade witnessed significant progress in angle-resolved photoemission spectroscopy (ARPES) and its applications. Today, ARPES experiments with 2-meV energy resolution and $0.2\ifmmode^\circ\else\textdegree\fi{}$ angular resolution are a reality even for photoemission on solids. These technological advances and the improved sample quality have enabled ARPES to emerge as a leading tool in the investigation of the high-${T}_{c}$ superconductors. This paper reviews the most recent ARPES results on the cuprate superconductors and their insulating parent and sister compounds, with the purpose of providing an updated summary of the extensive literature. The low-energy excitations are discussed with emphasis on some of the most relevant issues, such as the Fermi surface and remnant Fermi surface, the superconducting gap, the pseudogap and $d$-wave-like dispersion, evidence of electronic inhomogeneity and nanoscale phase separation, the emergence of coherent quasiparticles through the superconducting transition, and many-body effects in the one-particle spectral function due to the interaction of the charge with magnetic and/or lattice degrees of freedom. Given the dynamic nature of the field, we chose to focus mainly on reviewing the experimental data, as on the experimental side a general consensus has been reached, whereas interpretations and related theoretical models can vary significantly. The first part of the paper introduces photoemission spectroscopy in the context of strongly interacting systems, along with an update on the state-of-the-art instrumentation. The second part provides an overview of the scientific issues relevant to the investigation of the low-energy electronic structure by ARPES. The rest of the paper is devoted to the experimental results from the cuprates, and the discussion is organized along conceptual lines: normal-state electronic structure, interlayer interaction, superconducting gap, coherent superconducting peak, pseudogap, electron self-energy, and collective modes. Within each topic, ARPES data from the various copper oxides are presented.

https://arxiv.org/pdf/cond-mat/0208504.pdf

Angle-resolved photoemission studies of the cuprate superconductors

Rydberg atoms with principal quantum number $n⪢1$ have exaggerated atomic properties including dipole-dipole interactions that scale as ${n}^{4}$ and radiative lifetimes that scale as ${n}^{3}$. It was proposed a decade ago to take advantage of these properties to implement quantum gates between neutral atom qubits. The availability of a strong long-range interaction that can be coherently turned on and off is an enabling resource for a wide range of quantum information tasks stretching far beyond the original gate proposal. Rydberg enabled capabilities include long-range two-qubit gates, collective encoding of multiqubit registers, implementation of robust light-atom quantum interfaces, and the potential for simulating quantum many-body physics. The advances of the last decade are reviewed, covering both theoretical and experimental aspects of Rydberg-mediated quantum information processing.

Quantum information with Rydberg atoms

The technique of stimulated Raman adiabatic passage (STIRAP), which allows efficient and selective population transfer between quantum states without suffering loss due to spontaneous emission, was introduced in 1990 (Gaubatz \emph{et al.}, J. Chem. Phys. \textbf{92}, 5363, 1990). Since then STIRAP has emerged as an enabling methodology with widespread successful applications in many fields of physics, chemistry and beyond. This article reviews the many applications of STIRAP emphasizing the developments since 2000, the time when the last major review on the topic was written (Vitanov \emph{et al.}, Adv. At. Mol. Opt. Phys. \textbf{46}, 55, 2001). A brief introduction into the theory of STIRAP and the early applications for population transfer within three-level systems is followed by the discussion of several extensions to multi-level systems, including multistate chains and tripod systems. The main emphasis is on the wide range of applications in atomic and molecular physics (including atom optics, cavity quantum electrodynamics, formation of ultracold molecules, precision experiments, etc.), quantum information (including single- and two-qubit gates, entangled-state preparation, etc.), solid-state physics (including processes in doped crystals, nitrogen-vacancy centers, superconducting circuits, etc.), and even some applications in classical physics (including waveguide optics, frequency conversion, polarization optics, etc.). Promising new prospects for STIRAP are also presented (including processes in optomechanics, detection of parity violation in molecules, spectroscopy of core-nonpenetrating Rydberg states, and population transfer with X-ray pulses).

Stimulated Raman adiabatic passage in physics, chemistry, and beyond

The transition wave number from the EF Σ1g+(v=0,N=1) energy level of ortho-H2 to the 54p11(0) Rydberg state below the X+ Σ2g+(v+=0,N+=1) ground state of ortho-H2+ has been measured to be 25 209.997 56±(0.000 22)statistical±(0.000 07)systematic cm−1. Combining this result with previous experimental and theoretical results for other energy level intervals, the ionization and dissociation energies of the hydrogen molecule have been determined to be 124 417.491 13(37) and 36 118.069 62(37) cm−1, respectively, which represents a precision improvement over previous experimental and theoretical results by more than one order of magnitude. The new value of the ionization energy can be regarded as the most precise and accurate experimental result of this quantity, whereas the dissociation energy is a hybrid experimental-theoretical determination.

/pdf/determination-of-the-ionization-and-dissociation-energies-of-39a6umn1sq.pdf

Determination of the ionization and dissociation energies of the hydrogen molecule.

Sequences of pulsed electric fields have been designed and tested that enable a higher selectivity in the pulsed field ionization of high Rydberg states (n⩾100) than has so far been possible. The enhanced selectivity originates from the permutation of the parabolic quantum numbers n1 and n2 that is induced by a sufficiently rapid inversion of the electric field polarity during a pulse sequence. A reliable procedure, based on numerical simulations of the outcome of pulse field ionization sequences, has been developed to detect and control changes in the parabolic quantum numbers that can occur during a pulse sequence. The procedure can be used to assess under which conditions a clean permutation of the parabolic quantum numbers can be achieved. Unwanted randomization of m, n1 and n2, which reduces the selectivity of the field ionization process, can be avoided by minimizing the time intervals during which the electric field in the pulse sequence is almost zero. The high selectivity reached in the pulsed fi...

Selective field ionization of high Rydberg states: Application to zero-kinetic-energy photoelectron spectroscopy

A three-dimensional trap for Rydberg atoms in selected Stark states has been realized experimentally. H atoms seeded in a supersonic expansion of Ar are excited to the low-field seeking n=30, k=25, |m|=0, 2 Rydberg-Stark states, decelerated from a mean initial velocity of 665 m/s to zero velocity in the laboratory frame and loaded into a three-dimensional electrostatic trap. The motion of the cold Rydberg atom cloud in the trap and the decay of the trapped atoms have been studied by pulsed electric field ionization and imaging techniques.

/pdf/demonstration-of-three-dimensional-electrostatic-trapping-of-56ik3780e9.pdf

Demonstration of three-dimensional electrostatic trapping of state-selected Rydberg atoms.

The Rydberg states with principal quantum number located below the ground state of the ion have been studied by pulsed field ionization following single-photon excitation out of the ground state of Ar. The linewidth of the tunable extreme ultraviolet (XUV) laser source used enabled high-resolution measurement of the Stark effect over a wide range of principal quantum numbers and electric field strengths. Particular attention was given to the ionization of high Rydberg states induced by DC and pulsed electric fields. The lowering (expressed in ) of the ionization threshold by DC electric fields is accurately described by when the electric field strength F is expressed in , a result that is in good agreement with predictions of the classical saddle-point model for field ionization. The field-ionization threshold is very sharp: its width decreases from 0.7 to when the DC field strength is reduced from 580 to . Apart from the Stark states located in a very narrow energy range around the saddle-point energy in the potential which are found to ionize very slowly, all Stark states located below the saddle-point energy have lifetimes exceeding several microseconds, whereas those located beyond the saddle-point energy ionize within less than 20 ns. The very slow field ionization that is observed in a narrow range of energies around the classical saddle point can be used to obtain high state selectivity in the pulsed field ionization. The pulsed field-ionization behaviour observed in argon suggests that the rule that is now commonly assumed in the analysis of pulsed-field-ionization (PFI) zero-kinetic-energy (ZEKE) spectra to describe the low-wavenumber onset of a line relative to the position of the corresponding field-free ionization threshold must be used with caution.

https://iopscience.iop.org/article/10.1088/0953-4075/31/8/020/pdf

High Rydberg states of argon: Stark effect and field-ionization properties

General rovibronic symmetry selection rules, which are applicable to any molecular symmetry, have been obtained for the photoionization of polyatomic molecules. The use of the molecular symmetry groups leads to a particularly transparent derivation. The photoelectron is characterized by a partial wave expansion in the orbital angular momentum quantum number l. For a given value of l, one-photon electric dipole transitions can only occur between neutral and ionic states that obey the rovibronic symmetry conditions Γrve (neutral) ⊗ Γrve (ion) ⊃ Γ* for l even and Γrve(neutral) ⊗ Γrve(ion) ⊃ Γ(s) for l odd, where Γ(s) and Γ* represent the totally symmetric and the antisymmetric representations, respectively. Combined with the wellknown angular momentum conservation selection rule Δ J = J + - J = l + , l + ½,…, l - ½, l - [EQUATION](where J + and J represent the total angular momentum quantum number of the ionic and the neutral state between which the photoelectronic transition occurs), these symmetry selectio...

FrÃ©dÃ©ric Merkt

Papers

Determination of the ionization and dissociation energies of the hydrogen molecule.

Selective field ionization of high Rydberg states: Application to zero-kinetic-energy photoelectron spectroscopy

Demonstration of three-dimensional electrostatic trapping of state-selected Rydberg atoms.

High Rydberg states of argon: Stark effect and field-ionization properties

General symmetry selection rules for the photoionization of polyatomic molecules