A BCS wavefunction approach to the BEC-BCS crossover of exciton-polariton condensates

The crossover between low and high density regimes of exciton-polariton condensates is examined using a BCS wavefunction approach. Our approach is an extension of the BEC-BCS crossover theory for excitons, but includes a cavity photon field. The approach can describe both the low density limit, where the system can be described as a Bose-Einstein condensate (BEC) of exciton-polaritons, and the high density limit, where the system enters a photon dominated regime. In contrast to the exciton BEC-BCS crossover where the system approaches an electron-hole plasma, the polariton high density limit has strongly correlated electron-hole pairs. At intermediate densities, there is a regime with BCS-like properties, with a peak at non-zero momentum of the singlet pair function. We calculate the expected photoluminescence and give several experimental signatures of the crossover.Comment: 10 pages, 3 figure

The negative Bogoliubov dispersion in exciton-polariton condensates

Bogoliubov's theory states that self-interaction effects in Bose-Einstein condensates produce a characteristic linear dispersion at low momenta. One of the curious features of Bogoliubov's theory is that the new quasiparticles in the system are linear combinations of creation and destruction operators of the bosons. In exciton-polariton condensates, this gives the possibility of directly observing the negative branch of the Bogoliubov dispersion in the photoluminescence (PL) emission. Here we theoretically examine the PL spectra of exciton-polariton condensates taking into account of reservoir effects. At sufficiently high excitation densities, the negative dispersion becomes visible. We also discuss the possibility for relaxation oscillations to occur under conditions of strong reservoir coupling. This is found to give a secondary mechanism for making the negative branch visible

Nonadiabatic nonlinear non-Hermitian quantized pumping

We analyze a quantized pumping in a nonlinear non-Hermitian photonic system with nonadiabatic driving. The photonic system is made of a waveguide array, where the distances between adjacent waveguides are modulated. It is described by the Su-Schrieffer-Heeger model together with a saturated nonlinear gain term and a linear loss term. A topological interface state between the topological and trivial phases is stabilized by the combination of a saturated nonlinear gain term and a linear loss term. We study the pumping of the topological interface state. We define the transfer-speed ratio $\omega /\Omega$ by the ratio of the pumping speed $$ of the center of mass of the wave packet to the driving speed $\Omega$ of the topological interface. It is quantized as $\omega /\Omega =1$ in the adiabatic limit. It remains to be quantized for slow driving even in the nonadiabatic regime, which is a nonadiabatic quantized pump. On the other hand, there is almost no pump for fast driving. We find a transition in pumping as a function of the driving speed.Comment: 6 pages, 6 figure

LambertEaton筋無力症候群治療薬3,4diaminopyridineの体内動態に関する研究

13301甲第4132号博士（薬学）金沢大学博士論文本文Full 以下に掲載予定：International Journal of Clinical Pharmacology and Therapeutics. Dustri-Verlag Dr. Karl Feistle GmbH & Co. KG. 共著者：Natsuko Ishida, Erina Kobayashi, Yuya Kondo, Ryo Matsushita, Kiyonobu Komai

自閉スペクトラム症の成人における感覚処理異常と事象関連電位との関連についての予備的観察

Aim: Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is thought to involve a variety of neurophysiological characteristics. Event-related potentials (ERPs) reflect cognitive functions in the brain's cognitive processing. In this study, we investigated differences in P300 and N100 of ERPs between ASD and typically developing groups and focused on the relationship between the components of ERPs and measures of autistic traits and sensory processing characteristics. Methods: ERPs were measured in 96 subjects in the ASD group and 62 subjects in the age- and sex-adjusted typically developing group. Correlations between each component and the scores of the Autism-Spectrum Quotient Japanese version (AQ-J) and the Adolescent and Adult Sensory Profile (AASP) were also evaluated. Results: The ASD group showed a significant decrease in the amplitude of N100 at C3. Furthermore, a negative correlation was found between lower amplitude at C3 of N100 and low registered sensory scores in both groups. Conclusion: Our findings imply that the N100 amplitude at C3 could be a potential indicator for examining the neurophysiological traits of ASD; however, these results should be interpreted with caution due to their preliminary nature. These tentative insights into sensory processing anomalies may be discernible in specific subsets of the ASD population, providing a foundation for future investigative pathways.権利情報：© 2024 The Authors. Psychiatry and Clinical Neurosciences Reports published by John Wiley & Sons Australia, Ltd on behalf of Japanese Society of Psychiatry and Neurology. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes

Reduced prefrontal hemodynamic responses measured using near-infrared spectroscopy in adults with autism spectrum disorder

AimFunctional neuroimaging studies have suggested that prefrontal cortex dysfunction occurs in individuals with autism spectrum disorder (ASD). Near-infrared spectroscopy (NIRS) is a noninvasive optical tool used to investigate oxygenation and hemodynamic responses in the cerebral cortex by measuring changes in oxygenated hemoglobin. Previous studies using NIRS have suggested that male children with ASD exhibit reduced hemodynamic responses in the dorsolateral prefrontal cortex; however, only a few studies examined this response in adults with ASD.MethodsWe examined the characteristics of prefrontal hemodynamic responses in 114 adults with ASD and 84 typically developing controls. Relative concentrations of oxygenated hemoglobin were measured with frontal probes every 0.1 s during the Stroop color-word task, using 24-channel NIRS.ResultsOur findings demonstrated that the oxygenated hemoglobin changes in the ASD group were significantly smaller than those in the control group at channels 19, 20, 23, and 24- located over the orbitofrontal cortex and frontal pole (p <0.05 for all three channels). The differences in oxygenated hemoglobin changes at Ch 20 were significantly correlated with the Autism-Spectrum Quotient Japanese version (AQ-J) total score and attention switching score, which is a symptom cluster of AQ-J (p = 0.043 and p = 0.009, respectively).ConclusionAdults with ASD have reduced prefrontal hemodynamic responses as measured using near-infrared spectroscopy and the reduced activity of the frontal pole in particular is related to reduced attentional function

Highly excited exciton-polariton condensates

This research was supported by the Japan Society for the Promotion of Science (JSPS) through its FIRST Program and KAKENHI Grant Numbers 24740277 and 25800181, a Space and Naval Warfare Systems (SPAWAR) Grant Number N66001-09-1-2024, the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), the National Institution of Information and Communication Technology (NICT), the joint study program at Institute for Molecular Science. T. H. acknowledges the support of Toray Science Foundation, KDDI Foundation, the Asahi Glass Foundation, ther Murata Science Foundation, and REFEC. T.B. acknowledges the support of the Shanghai Research Challenge Fund, New York University Global Seed Grants for Collaborative Research, National Natural Science Foundation of China (Grant No. 61571301), the Thousand Talents Program for Distinguished Young Scholars (Grant No. D1210036A), and the NSFC Research Fund for International Young Scientists (Grant No. 11650110425).Exciton polaritons are a coherent electron-hole-photon (e-h-p) system where condensation has been observed in semiconductor microcavities. In contrast to equilibrium Bose-Einstein condensation (BECs) for long lifetime systems, polariton condensates have a dynamical nonequilibrium feature owing to the similar physical structure that they have to semiconductor lasers. One of the distinguishing features of a condensate to a laser is the presence of strong coupling between the matter and photon fields. Irrespective of its equilibrium or nonequilibrium nature, exciton polaritons have been observed to maintain strong coupling. We show that by investigating the high-density regime of exciton-polariton condensates, the negative branch is directly observed in photoluminescence. This is evidence that the present e-h-p system is still in the strong-coupling regime, contrary to past results where the system reduced to standard lasing at high density.PostprintPostprintPeer reviewe