scholarly journals Observation of superfluidity in a strongly correlated two-dimensional Fermi gas

Science ◽  
2021 ◽  
Vol 372 (6544) ◽  
pp. 844-846
Author(s):  
Lennart Sobirey ◽  
Niclas Luick ◽  
Markus Bohlen ◽  
Hauke Biss ◽  
Henning Moritz ◽  
...  
Keyword(s):  
Periodic Potential ◽  
Direct Evidence ◽  
Interaction Strength ◽  
Fermi Gas ◽  
Model Systems ◽  
Strongly Correlated ◽  
Two Dimensional ◽  
Strong Correlations ◽  
Critical Temperatures ◽  
Reduced Dimensionality

Understanding how strongly correlated two-dimensional (2D) systems can give rise to unconventional superconductivity with high critical temperatures is one of the major unsolved problems in condensed matter physics. Ultracold 2D Fermi gases have emerged as clean and controllable model systems to study the interplay of strong correlations and reduced dimensionality, but direct evidence of superfluidity in these systems has been missing. We demonstrate superfluidity in an ultracold 2D Fermi gas by moving a periodic potential through the system and observing no dissipation below a critical velocity vc. We measure vc as a function of interaction strength and find a maximum in the crossover regime between bosonic and fermionic superfluidity. Our measurements enable systematic studies of the influence of reduced dimensionality on fermionic superfluidity.

scholarly journals An ideal Josephson junction in an ultracold two-dimensional Fermi gas

Science ◽  
2020 ◽  
Vol 369 (6499) ◽  
pp. 89-91 ◽  
Author(s):  
Niclas Luick ◽  
Lennart Sobirey ◽  
Markus Bohlen ◽  
Vijay Pal Singh ◽  
Ludwig Mathey ◽  
...  
Keyword(s):  
Josephson Junction ◽  
High Temperature Superconductors ◽  
Fermi Gas ◽  
Current Phase ◽  
Strongly Correlated ◽  
Two Dimensional ◽  
Weakly Bound ◽  
Ideal Model System ◽  
Sinusoidal Current ◽  
2D Fermi Gas

The role of reduced dimensionality in high-temperature superconductors is still under debate. Recently, ultracold atoms have emerged as an ideal model system to study such strongly correlated two-dimensional (2D) systems. Here, we report on the realization of a Josephson junction in an ultracold 2D Fermi gas. We measure the frequency of Josephson oscillations as a function of the phase difference across the junction and find excellent agreement with the sinusoidal current phase relation of an ideal Josephson junction. Furthermore, we determine the critical current of our junction in the crossover from tightly bound molecules to weakly bound Cooper pairs. Our measurements clearly demonstrate phase coherence and provide strong evidence for superfluidity in a strongly interacting 2D Fermi gas.

Polarons and molecules in a mixed-dimensional Fermi gas

2021 ◽  
pp. 2150354
Author(s):  
Baihua Gong ◽  
Xin-Hui Zhang
Keyword(s):  
Effective Mass ◽  
Impurity Atom ◽  
Variational Approach ◽  
Interaction Strength ◽  
Ground States ◽  
Fermi Gas ◽  
Energy Difference ◽  
Two Dimensional ◽  
Spatial Constraint ◽  
Polaron Energy

We address the problem of a single impurity atom moving in a two-dimensional (2D) layer immersed in a 3D Fermi gas. Using a variational approach, we show that in this mixed-dimensional (MD) system, there is a transition between polaron and molecule ground states, similar to the case of pure 3D. Moreover, we find that the attractive polaron energy in MD is higher than that in 3D, while molecular energy in MD is lower than that in 3D, which leads to a shift of the critical interaction strength of transition. Further analysis shows that the energy difference between 3D and MD systems is attributed to the increment of the effective mass of the impurity, which is induced by the spatial constraint on the impurity.

Direct evidence for two-dimensional oxide-ion diffusion in the hexagonal perovskite-related oxide Ba3MoNbO8.5−δ

2019 ◽  
Vol 7 (23) ◽  
pp. 13910-13916 ◽  
Author(s):  
Masatomo Yashima ◽  
Takafumi Tsujiguchi ◽  
Kotaro Fujii ◽  
Eiki Niwa ◽  
Shunta Nishioka ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Two Dimensional ◽  
Ion Diffusion ◽  
Diffusion Paths ◽  
Oxide Ion

Experimentally visualized two-dimensional O2−–O2–O3– diffusion paths rotating around Ba cations in oxygen deficient Ba3MoNbO8.5−δat 1100 °C.

scholarly journals Nanometer-Thick [(FPEA)2PbX4; X=I, Br] 2D Halide Perovskite Based Thin Films for Pollutant Detection and Nonconventional Photocatalytic Degradation

2021 ◽  
Author(s):  
Arindam Mondal ◽  
Akash Lata ◽  
Aarya Prabhakaran ◽  
Satyajit Gupta
Keyword(s):  
Thin Films ◽  
Photocatalytic Degradation ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Reduced Dimensionality ◽  
P Application ◽  
Halide Perovskites ◽  
Halide Perovskite ◽  
Pollutant Detection

Application of three-dimensional (3D)-halide perovskites (HaP) in photocatalysis encourages the new exercise with two-dimensional (2D) HaP based thin-films for photocatalytic degradation of dye. The reduced dimensionality to 2D-HaPs, with a...

scholarly journals Single-File Water Flux Through Two-Dimensional Nanoporous Membranes

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Myung Eun Suk
Keyword(s):  
Water Flux ◽  
Interaction Strength ◽  
High Water ◽  
Potential Of Mean Force ◽  
Proximal Region ◽  
Dominant Factor ◽  
Chemical Characteristics ◽  
Nanoporous Membranes ◽  
Two Dimensional ◽  
Single File

Abstract Recent advances in the development of two-dimensional (2D) materials have facilitated a wide variety of surface chemical characteristics obtained by composing atomic species, pore functionalization, etc. The present study focused on how chemical characteristics such as hydrophilicity affects the water transport rate in hexagonal 2D membranes. The membrane–water interaction strength was tuned to change the hydrophilicity, and the sub-nanometer pore was used to investigate single-file flux, which is known to retain excellent salt rejection. Due to the dewetting behavior of the hydrophobic pore, the water flux was zero or nominal below the threshold interaction strength. Above the threshold interaction strength, water flux decreased with an increase in interaction strength. From the potential of mean force analysis and diffusion coefficient calculations, the proximal region of the pore entrance was found to be the dominant factor degrading water flux at the highly hydrophilic pore. Furthermore, the superiority of 2D membranes over 3D membranes appeared to depend on the interaction strength. The present findings will have implications in the design of 2D membranes to retain a high water filtration rate.

scholarly journals Development of the Psychological Insight Questionnaire among a sample of people who have consumed psilocybin or LSD

2021 ◽  
pp. 026988112096787
Author(s):  
Alan K Davis ◽  
Frederick S Barrett ◽  
Sara So ◽  
Natalie Gukasyan ◽  
Thomas C Swift ◽  
...  
Keyword(s):  
Life Satisfaction ◽  
Longitudinal Research ◽  
Psychological Flexibility ◽  
Well Being ◽  
Survey Study ◽  
Strongly Correlated ◽  
Strong Correlations ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Therapeutic Outcomes

Background: Several measures have been developed to examine acute psychedelic effects (e.g. mystical-type and challenging experiences), but no measure assesses acute psychologically insightful experiences that may occur during psychedelic experiences. Aim: The purpose of this study was to develop and examine the psychometric properties of the Psychological Insight Questionnaire. Method: A cross-sectional survey study among psilocybin and LSD users. Respondents ( n=1661; Mage=22.9, standard deviation=8.5; Caucasian/White=83%; non-Hispanic=91%; men=72%; United States resident=66%) completed an Internet-based survey. Results: The Psychological Insight Questionnaire consists of 23 items with two subscales: (a) Avoidance and Maladaptive Patterns Insights and (b) Goals and Adaptive Patterns Insights. Construct validity of the Psychological Insight Questionnaire was supported by strong correlations of the Psychological Insight Questionnaire (and Avoidance and Maladaptive Patterns Insights and Goals and Adaptive Patterns Insights subscales) scores with the insight subscale of the Session Impacts Scale, and weak-to-moderate correlations with the Mystical Experiences and Challenging Experiences Questionnaires. Furthermore, Psychological Insight Questionnaire (and Avoidance and Maladaptive Patterns Insights and Goals and Adaptive Patterns Insights subscales) scores were moderately-to-strongly correlated with retrospectively reported increases in psychological flexibility, and well-being/life satisfaction that were attributed to a memorable psychedelic experience. Lastly, incremental validity was established showing that the Psychological Insight Questionnaire (and Avoidance and Maladaptive Patterns Insights subscale) scores predict unique variance in changes in psychological flexibility, and Psychological Insight Questionnaire (and Avoidance and Maladaptive Patterns Insights and Goals and Adaptive Patterns Insights subscales) scores predict changes in well-being and life satisfaction, beyond measures of acute mystical-type and challenging effects. Conclusions: The Psychological Insight Questionnaire has the potential to extend the understanding of the acute and enduring effects of psychedelics. Further longitudinal research is necessary to determine the long-term predictive validity of the Psychological Insight Questionnaire and to examine the role of psychological insight in predicting therapeutic outcomes.

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