日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

Annual review of condensed matter physics

Summary form only given. Fundamental processes in atoms, molecules, as well as condensed matter are triggered or mediated by the motion of electrons inside or between atoms. Electronic dynamics on atomic length scales tends to unfold within tens to thousands of attoseconds (1 attosecond [as] = 10-18 s). Recent breakthroughs in laser science are now opening the door to watching and controlling these hitherto inaccessible microscopic dynamics. The key to accessing the attosecond time domain is the control of the electric field of (visible) light, which varies its strength and direction within less than a femtosecond (1 femtosecond = 1000 attoseconds). Atoms exposed to a few oscillations cycles of intense laser light are able to emit a single extreme ultraviolet (XUV) burst lasting less than one femtosecond. Full control of the evolution of the electromagnetic field in laser pulses comprising a few wave cycles have recently allowed the reproducible generation and measurement of isolated sub-femtosecond XUV pulses, demonstrating the control of microscopic processes (electron motion and photon emission) on an attosecond time scale. These tools have enabled us to visualize the oscillating electric field of visible light with an attosecond "oscilloscope", to control single-electron and probe multi-electron dynamics in atoms, molecules and solids. Recent experiments hold promise for the development of an attosecond X-ray source, which may pave the way towards 4D electron imaging with sub-atomic resolution in space and time.

Attosecond Physics

High-order harmonic generation is a nonlinear optical process that enables the creation of light pulses at frequencies much higher than that from a seed laser. The host medium for this interaction is typically a gas. Now, the process has been observed in a bulk crystalline solid with important implications for attosecond science.

/pdf/observation-of-high-order-harmonic-generation-in-a-bulk-2ujjcse9va.pdf

Observation of high-order harmonic generation in a bulk crystal

Journal of Physics Condensed Matter: Preface

A systematic experimental study of the ionization of argon by mid-infrared light confirms half-a-century-old predictions and paves the way to the development of brighter, shorter attosecond pulse sources.

/pdf/scaling-strong-field-interactions-towards-the-classical-12cygbw1je.pdf

Scaling strong-field interactions towards the classical limit

We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by using self-phase stabilized 330 μJ 55 fs pulses at 2 μm produced via difference-frequency generation in a Ti:sapphire-pumped optical parametric amplifier. The ultrabroadband 2 μm carrier-wavelength output is self-compressed below 3 optical cycles and has a 270 μJ pulse energy. The self-locked phase offset of the 2 μm difference-frequency field is preserved after filamentation. This is to our knowledge the first experimental realization of pulse compression in optical filaments at mid-IR wavelengths (λ>0.8 μm).

Intense self-compressed, self-phase-stabilized few-cycle pulses at 2 μm from an optical filament

The group delay dispersion, also known as the attochirp, of high-order harmonics generated in gases has been identified as the main intrinsic limitation to the duration of Fourier-synthesized attosecond pulses. Theory implies that the attochirp, which is inversely proportional to the laser wavelength, can be decreased at longer wavelength. Here we report the first measurement of the wavelength dependence of the attochirp using an all-optical, in situ method [N. Dudovich et al., Nature Phys. 2, 781 (2006)]. We show that a $2\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ driving wavelength reduces the attochirp with respect to $0.8\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ at comparable intensities.

/pdf/attosecond-synchronization-of-high-order-harmonics-from-2ukxjqb6sz.pdf

Attosecond Synchronization of High-Order Harmonics from Midinfrared Drivers

High harmonic generation (HHG) is used to measure the spectral phase of the recombination dipole matrix element (RDM) in argon over a broad frequency range that includes the 3p Cooper minimum (CM). The measured RDM phase agrees well with predictions based on the scattering phases and amplitudes of the interfering s- and d-channel contributions to the complementary photoionization process. The reconstructed attosecond bursts that underlie the HHG process show that the derivative of the RDM spectral phase, the group delay, does not have a straightforward interpretation as an emission time, in contrast to the usual attochirp group delay. Instead, the rapid RDM phase variation caused by the CM reshapes the attosecond bursts.

/pdf/attosecond-pulse-shaping-around-a-cooper-minimum-keyk17y4rg.pdf

Attosecond pulse shaping around a Cooper minimum.

We investigate the spin-resolved transport properties, such as the linear conductance and the tunnel magnetoresistance, of a double quantum dot device attached to ferromagnetic leads and look for signatures of SU(4) symmetry in the Kondo regime We show that the transport behavior greatly depends on the magnetic configuration of the device, and the spin-SU(2) as well as the orbital and spin-SU(4) Kondo effects become generally suppressed when the magnetic configuration of the leads varies from the antiparallel to the parallel one Furthermore, a finite spin polarization of the leads lifts the spin degeneracy and drives the system from the SU(4) to an orbital-SU(2) Kondo state We analyze in detail the crossover and show that the Kondo temperature between the two fixed points has a non-monotonic dependence on the degree of spin polarization of the leads In terms of methods used, we characterize transport by using a combination of analytical and numerical renormalization group approaches

Razvan Chirla

Papers

Scaling strong-field interactions towards the classical limit

Intense self-compressed, self-phase-stabilized few-cycle pulses at 2 μm from an optical filament

Attosecond Synchronization of High-Order Harmonics from Midinfrared Drivers

Attosecond pulse shaping around a Cooper minimum.

SU(4) Kondo effect in double quantum dots with ferromagnetic leads