arXiv subjects

Yosuke Kayanuma

Publications and source records attributed to Yosuke Kayanuma.

17 recordsLinked to original sources

arXiv2025

Attosecond-resolved coherent control of zone-folded acoustic phonons in silicon carbide

Zone-folded acoustic phonons (6 THz) in 4H silicon carbide (SiC) have been coherently excited using a femtosecond near-infrared pulse and measured through transient reflectivity with a pump and probe protocol. Their amplitude is coherently controlled with 300-attoseconds precision and the results show interference fringe patterns due to electronic and phonon interference. The results are well reproduced by a model calculation with two electronic and phonon levels and an impulsive stimulated Raman process. Using the model, we obtain the analytical form of the coherent control scheme at an off-resonant condition.

cond-mat.mtrl-sci↗

arXiv2024

Dual role of longitudinal optical phonons for generation of coherent oscillations in gallium arsenide under optical pumping

We present a novel and simple picture of the generation dynamics of coherent longitudinal optical (LO) phonons and LO-phonon-plasmon-coupled (LOPC) modes by the ultrafast infrared pump-pulses in gallium arsenide (GaAs) employing the low-temperature approximation. LO phonons exhibit a pronounced coupling with plasmons formed by the optically excited electrons in the excited states of GaAs. This coupling results in the coherent oscillation of the LOPC modes in the excited states. The pump pulse also induces stimulated Raman scattering, which generates the coherent LO-phonon oscillation in the ground state. This picture is incorporated into a simplified model, and the time evolution of the density operator is calculated using the Lindblad-type quantum master equation. The theoretical results explain well the reported experimental results on the coherent oscillation of LO phonons and LOPC modes observed through transient reflection measurements. Above all, our model provides a natural reason for the simultaneous manifestation of the LO phonons and the LOPC modes.

cond-mat.mtrl-sci↗

arXiv2022

Floquet-Landau-Zener interferometry: Usefulness of the Floquet theory in pulse-laser-driven systems

We develop the Landau-Zener transfer matrix theory for the instantaneous Floquet states (IFSs) for quantum systems driven by strong pulse lasers. Applying this theory to the pulse excitation probability in two-level quantum systems, we show unexpectedly good quantitative agreements for few-cycle pulses. This approach enables us to qualitatively understand the probability's peculiar behaviors as quantum path interference between IFSs. We also study the pulse-width dependence, finding that this Floquet-state interpretation remains useful for shorter pulses down to 2-cycle ones in the present model. These results imply that the Floquet theory is meaningful in experimental few-cycle lasers if applied appropriately in the sense of IFSs.

cond-mat.mes-hall↗

arXiv2021

Transmission of a single electron through a Berry's ring

A theoretical model of transmission and reflection of an electron with spin is proposed for a mesoscopic ring with rotating localized magnetic moment. This model may be realized in a pair of domain walls connecting two ferromagnetic domains with opposite magnetization. If the localized magnetic moment and the traveling spin is ferromagnetically coupled and if the localized moment rotates with opposite chirality in the double-path, our system is formulated in the model of an emergent spin-orbit interaction in a ring. The scattering problem for the transmission spectrum of the traveling spin is solved both in a single path and a double path model. In the double path, the quantum-path interference changes dramatically the transmission spectrum due to the effect of the Berry's phase. Specifically, the spin-flip transmission and reflection are both strictly forbidden.

cond-mat.mes-hall↗

arXiv2019

Coherent control of 40-THz optical phonons in diamond using femtosecond optical pulses

Coherent control is an optical technique to manipulate quantum states of matter. The coherent control of 40-THz optical phonons in diamond was demonstrated by using a pair of sub-10-fs optical pulses. The optical phonons were detected via transient transmittance using a pump and probe protocol. The optical and phonon interferences were observed in the transient transmittance change and its behavior was well reproduced by quantum mechanical calculations with a simple model which consists of two electronic levels and shifted harmonic oscillators.

physics.optics↗

arXiv2019

Ultrafast Quantum-path Interferometry Revealing the Generation Process of Coherent Phonons

Optical dual-pulse pumping actively creates quantum-mechanical superposition of the electronic and phononic states in a bulk solid. We here made transient reflectivity measurements in an n-GaAs using a pair of relative-phase-locked femtosecond pulses and found characteristic interference fringes. This is a result of quantum-path interference peculiar to the dual-pulse excitation as indicated by theoretical calculation. Our observation reveals that the pathway of coherent phonon generation in the n-GaAs is impulsive stimulated Raman scattering at the displaced potential due to the surface-charge field, even though the photon energy lies in the opaque region.

cond-mat.mes-hall↗

arXiv2017

Coherent control theory and experiment of optical phonons in diamond

The coherent control of optical phonons has been experimentally demonstrated in various physical systems. While the transient dynamics for optical phonons can be explained by phenomenological models, the coherent control experiment cannot be explained due to the quantum interference. Here, we theoretically propose the generation and detection processes of the optical phonons and experimentally confirm our theoretical model using the diamond optical phonon by the double-pump-probe type experiment.

cond-mat.other↗

arXiv2016

Spectrally resolved detection in transient-reflectivity measurements of coherent optical phonons in diamond

Coherent optical phonons in bulk solid system play a crucial role in understanding and designing light-matter interactions and can be detected by the transient-reflectivity measurement. In this paper, we demonstrate spectrally resolved detection of coherent optical phonons in diamond from ultrashort infrared pump-probe measurements using optical band-pass filters. We show that this enhances the sensitivity approximately 35 times in measuring the coherent oscillations in the transient reflectivity compared with the commonly used spectrally integrated measurement. To explain this observation, we discuss its mechanism.

cond-mat.mes-hall↗

arXiv2015

Influence of pulse width and detuning on coherent phonon generation

We investigated the coherent phonon generation mechanism by irradiation of an ultrashort pulse with a simple two-level model. Our derived formulation shows that both impulsive stimulated Raman scattering (ISRS) and impulsive absorption (IA) simultaneously occur, and phonon wave packets are generated in the electronic ground and excited states by ISRS and IA, respectively. We identify the dominant process from the amplitude of the phonon oscillation. For short pulse widths, ISRS is very small and becomes larger as the pulse width increases. We also show that the initial phase is dependent on the pulse width and the detuning.

cond-mat.mes-hall↗

arXiv2008

Coherent destruction of tunneling, dynamic localization and the Landau-Zener formula

We clarify the internal relationship between the coherent destruction of tunneling (CDT) for a two-state model and the dynamic localization (DL) for a one-dimensional tight-binding model, under the periodical driving field. The time-evolution of the tight-binding model is reproduced from that of the two-state model by a mapping of equation of motion onto a set of ${\rm SU}(2)$ operators. It is shown that DL is effectively an infinitely large dimensional representation of the CDT in the ${\rm SU}(2)$ operators. We also show that both of the CDT and the DL can be interpreted as a result of destructive interference in repeated Landau-Zener level-crossings.

cond-mat.mes-hall↗

arXiv2007

Dissipative Landau-Zener transitions of a qubit: bath-specific and universal behavior

We study Landau-Zener transitions in a qubit coupled to a bath at zero temperature. A general formula is derived that is applicable to models with a non-degenerate ground state. We calculate exact transition probabilities for a qubit coupled to either a bosonic or a spin bath. The nature of the baths and the qubit-bath coupling is reflected in the transition probabilities. For diagonal coupling, when the bath causes energy fluctuations of the diabatic qubit states but no transitions between them, the transition probability coincides with the standard LZ probability of an isolated qubit. This result is universal as it does not depend on the specific type of bath. For pure off-diagonal coupling, by contrast, the tunneling probability is sensitive to the coupling strength. We discuss the relevance of our results for experiments on molecular nanomagnets, in circuit QED, and for the fast-pulse readout of superconducting phase qubits.

cond-mat.mes-hall↗

arXiv2007

Recoil effects of photoelectrons in a solid

High energy resolution C 1$s$ photoelectron spectra of graphite were measured at the excitation energy of 340, 870, 5950 and 7940eV using synchrotron radiation. On increasing the excitation energy, i.e., increasing kinetic energy of the photoelectron, the bulk origin C 1$s$ peak position shifts to higher binding energies. This systematic shift is due to the kinetic energy loss of the high-energy photoelectron by kicking the atom, and is clear evidence of the recoil effect in photoelectron emission. It is also observed that the asymmetric broadening increases for the higher energy photoelectrons. All these recoil effects can be quantified in the same manner as the Mössbauer effect for $γ$-ray emission from nuclei embedded in crystals.

cond-mat.other↗

arXiv2006

Quantum state preparation in circuit QED via Landau-Zener tunneling

We study a qubit undergoing Landau-Zener transitions enabled by the coupling to a circuit-QED mode. Summing an infinite-order perturbation series, we determine the exact nonadiabatic transition probability for the qubit, being independent of the frequency of the QED mode. Possible applications are single-photon generation and the controllable creation of qubit-oscillator entanglement.

cond-mat.mes-hall↗

arXiv2006

Gauging a quantum heat bath with dissipative Landau-Zener transitions

We calculate the exact Landau-Zener transitions probabilities for a qubit with arbitrary linear coupling to a bath at zero temperature. The final quantum state exhibits a peculiar entanglement between the qubit and the bath. In the special case of a diagonal coupling, the bath does not influence the transition probability, whatever the speed of the Landau-Zener sweep. It is proposed to use Landau-Zener transitions to determine both the reorganization energy and the integrated spectral density of the bath. Possible applications include circuit QED and molecular nanomagnets.

cond-mat.mes-hall↗

arXiv2005

Landau-Zener transitions in qubits controlled by electromagnetic fields

We investigate the influence of a dipole interaction with a classical radiation field on a qubit during a continuous change of a control parameter. In particular, we explore the non-adiabatic transitions that occur when the qubit is swept with linear speed through resonances with the time-dependent interaction. Two classical problems come together in this model: the Landau-Zener and the Rabi problem. The probability of Landau-Zener transitions now depends sensitively on the amplitude, the frequency and the phase of the Rabi interaction. The influence of the static phase turns out to be particularly strong, since this parameter controls the time-reversal symmetry of the Hamiltonian. In the limits of large and small frequencies, analytical results obtained within a rotating-wave approximation compare favourably with a numerically exact solution. Some physical realizations of the model are discussed, both in microwave optics and in magnetic systems.

cond-mat.mes-hall↗

arXiv2004

Nonadiabatic Electron Manipulation in Quantum-Dot Arrays

A novel method of coherent manipulation of the electron tunneling in quantum-dots is proposed, which utilizes the quantum interference in nonadiabatic double-crossing of the discrete energy levels. In this method, we need only a smoothly varying gate voltage to manipulate electrons, without a sudden switching-on and off. A systematic design of a smooth gate-pulse is presented with a simple analytic formula to drive the two-level electronic state to essentially arbitrary target state, and numerical simulations for complete transfer of an electron is shown for a coupled double quantum-dots and an array of quantum-dots. Estimation of the manipulation-time shows that the present method can be employed in realistic quantum-dots.

cond-mat.mes-hall↗

arXiv2001

Nonadiabatic Transition Probabilities in the Presence of Strong Dissipation at an Avoided Level Crossing Point

Dissipative effects on the nonadiabatic transition for the two and three level systems are studied. When the system is affected by a strong dissipation through the diabatic states, the exact transition probability is enumerated making use of the effective master equation. In the two-level system, we consider the case where the external field is swept from not only a negative large value but also from the resonant field, and the exact transition probabilities in these cases are derived. The transition probabilities are derived for the three-level system where the three diabatic states form only one avoided level crossing point. These probabilities are compared with the one in the pure quantum case obtained by Carroll and Hioe.

cond-mat.mtrl-sci↗