scholarly journals Kondo physics in antiferromagnetic Weyl semimetal Mn3+xSn1−x films

2020 ◽  
Vol 6 (35) ◽  
pp. eabc1977
Author(s):  
Durga Khadka ◽  
T. R. Thapaliya ◽  
Sebastian Hurtado Parra ◽  
Xingyue Han ◽  
Jiajia Wen ◽  
...  
Keyword(s):  
Kondo Effect ◽  
Energy Gap ◽  
Strongly Correlated ◽  
Strong Correlations ◽  
Strong Electron ◽  
Experimental Systems ◽  
Weyl Semimetal ◽  
Hall Effects ◽  
Kondo Physics ◽  
Gap Opening

Topology and strong electron correlations are crucial ingredients in emerging quantum materials, yet their intersection in experimental systems has been relatively limited to date. Strongly correlated Weyl semimetals, particularly when magnetism is incorporated, offer a unique and fertile platform to explore emergent phenomena in novel topological matter and topological spintronics. The antiferromagnetic Weyl semimetal Mn3Sn exhibits many exotic physical properties such as a large spontaneous Hall effect and has recently attracted intense interest. In this work, we report synthesis of epitaxial Mn3+xSn1−x films with greatly extended compositional range in comparison with that of bulk samples. As Sn atoms are replaced by magnetic Mn atoms, the Kondo effect, which is a celebrated example of strong correlations, emerges, develops coherence, and induces a hybridization energy gap. The magnetic doping and gap opening lead to rich extraordinary properties, as exemplified by the prominent DC Hall effects and resonance-enhanced terahertz Faraday rotation.

scholarly journals Oxygen vacancy-driven orbital multichannel Kondo effect in Dirac nodal line metals IrO2 and RuO2

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Sheng-Shiuan Yeh ◽  
Ta-Kang Su ◽  
An-Shao Lien ◽  
Farzaneh Zamani ◽  
Johann Kroha ◽  
...  
Keyword(s):  
Kondo Effect ◽  
High Temperature Superconductivity ◽  
Topological States Of Matter ◽  
Nodal Line ◽  
Metallic State ◽  
Strong Electron ◽  
Quantum Matter ◽  
Kondo Physics ◽  
Topological States ◽  
Weak Coupling Theory

Abstract Strong electron correlations have long been recognized as driving the emergence of novel phases of matter. A well recognized example is high-temperature superconductivity which cannot be understood in terms of the standard weak-coupling theory. The exotic properties that accompany the formation of the two-channel Kondo (2CK) effect, including the emergence of an unconventional metallic state in the low-energy limit, also originate from strong electron interactions. Despite its paradigmatic role for the formation of non-standard metal behavior, the stringent conditions required for its emergence have made the observation of the nonmagnetic, orbital 2CK effect in real quantum materials difficult, if not impossible. We report the observation of orbital one- and two-channel Kondo physics in the symmetry-enforced Dirac nodal line (DNL) metals IrO2 and RuO2 nanowires and show that the symmetries that enforce the existence of DNLs also promote the formation of nonmagnetic Kondo correlations. Rutile oxide nanostructures thus form a versatile quantum matter platform to engineer and explore intrinsic, interacting topological states of matter.

scholarly journals Band-selective gap opening by a C4-symmetric order in a proximity-coupled heterostructure Sr2VO3FeAs

2021 ◽  
Vol 118 (47) ◽  
pp. e2105190118
Author(s):  
Sunghun Kim ◽  
Jong Mok Ok ◽  
Hanbit Oh ◽  
Chang Il Kwon ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Energy Gap ◽  
Strongly Correlated ◽  
Strongly Correlated Electron ◽  
Fermi Surfaces ◽  
Correlated Electron Systems ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Broken Symmetries ◽  
Correlated Electron ◽  
Gap Opening

Complex electronic phases in strongly correlated electron systems are manifested by broken symmetries in the low-energy electronic states. Some mysterious phases, however, exhibit intriguing energy gap opening without an apparent signature of symmetry breaking (e.g., high-TC cuprates and heavy fermion superconductors). Here, we report an unconventional gap opening in a heterostructured, iron-based superconductor Sr2VO3FeAs across a phase transition at T0 ∼150 K. Using angle-resolved photoemission spectroscopy, we identify that a fully isotropic gap opens selectively on one of the Fermi surfaces with finite warping along the interlayer direction. This band selectivity is incompatible with conventional gap opening mechanisms associated with symmetry breaking. These findings, together with the unusual field-dependent magnetoresistance, suggest that the Kondo-type proximity coupling of itinerant Fe electrons to localized V spin plays a role in stabilizing the exotic phase, which may serve as a distinct precursor state for unconventional superconductivity.

scholarly journals Weyl–Kondo semimetal in heavy-fermion systems

2017 ◽  
Vol 115 (1) ◽  
pp. 93-97 ◽  
Author(s):  
Hsin-Hua Lai ◽  
Sarah E. Grefe ◽  
Silke Paschen ◽  
Qimiao Si
Keyword(s):  
Heavy Fermion ◽  
Kondo Effect ◽  
Degrees Of Freedom ◽  
Quantum Hall ◽  
Surface States ◽  
Natural Setting ◽  
Strongly Correlated ◽  
Strong Correlations ◽  
Fermion Systems ◽  
Fermi Arcs

Insulating states can be topologically nontrivial, a well-established notion that is exemplified by the quantum Hall effect and topological insulators. By contrast, topological metals have not been experimentally evidenced until recently. In systems with strong correlations, they have yet to be identified. Heavy-fermion semimetals are a prototype of strongly correlated systems and, given their strong spin-orbit coupling, present a natural setting to make progress. Here, we advance a Weyl–Kondo semimetal phase in a periodic Anderson model on a noncentrosymmetric lattice. The quasiparticles near the Weyl nodes develop out of the Kondo effect, as do the surface states that feature Fermi arcs. We determine the key signatures of this phase, which are realized in the heavy-fermion semimetal Ce3Bi4Pd3. Our findings provide the much-needed theoretical foundation for the experimental search of topological metals with strong correlations and open up an avenue for systematic studies of such quantum phases that naturally entangle multiple degrees of freedom.

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.

scholarly journals Electrical transport properties and Kondo effect in La1−xPrxNiO3−δ thin films

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Van Hien-Hoang ◽  
Nak-Kwan Chung ◽  
Heon-Jung Kim
Keyword(s):  
Thin Films ◽  
Electrical Transport ◽  
Kondo Effect ◽  
Magnetic Moments ◽  
Structural Disorder ◽  
Strongly Correlated ◽  
Electrical Transport Properties ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron

AbstractThe Kondo effect has been a topic of intense study because of its significant contribution to the development of theories and understanding of strongly correlated electron systems. In this work, we show that the Kondo effect is at work in La1−xPrxNiO3−δ (0 ≤ x ≤ 0.6) thin films. At low temperatures, the local magnetic moments of the 3d eg electrons in Ni2+, which form because of oxygen vacancies, interact strongly with itinerant electrons, giving rise to an upturn in resistivity with x ≥ 0.2. Observation of negative magnetoresistance, described by the Khosla and Fisher model, further supports the Kondo picture. This case represents a rare example of the Kondo effect, where Ni2+ acts as an impurity in the background of Ni3+. We suggest that when Ni2+ does not participate in the regular lattice, it provides the local magnetic moments needed to scatter the conduction electrons in the Kondo effect. These results offer insights into emergent transport behaviors in metallic nickelates with mixed Ni3+ and Ni2+ ions, as well as structural disorder.

scholarly journals Ultrafast dynamical Lifshitz transition

2021 ◽  
Vol 7 (17) ◽  
pp. eabd9275
Author(s):  
Samuel Beaulieu ◽  
Shuo Dong ◽  
Nicolas Tancogne-Dejean ◽  
Maciej Dendzik ◽  
Tommaso Pincelli ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Colossal Magnetoresistance ◽  
Surface Topology ◽  
Strongly Correlated ◽  
Many Body ◽  
Time Resolved ◽  
Weyl Semimetal ◽  
Lifshitz Transition ◽  
Fermi Surface Topology ◽  
Many Body Systems

Fermi surface is at the heart of our understanding of metals and strongly correlated many-body systems. An abrupt change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. While Lifshitz transitions have been demonstrated for a broad range of materials by equilibrium tuning of macroscopic parameters such as strain, doping, pressure, and temperature, a nonequilibrium dynamical route toward ultrafast modification of the Fermi surface topology has not been experimentally demonstrated. Combining time-resolved multidimensional photoemission spectroscopy with state-of-the-art TDDFT+U simulations, we introduce a scheme for driving an ultrafast Lifshitz transition in the correlated type-II Weyl semimetal Td-MoTe2. We demonstrate that this nonequilibrium topological electronic transition finds its microscopic origin in the dynamical modification of the effective electronic correlations. These results shed light on a previously unexplored ultrafast scheme for controlling the Fermi surface topology in correlated quantum materials.

Local Energy Gap Opening Induced by Hemin Dimerization in Aqueous Solution

2015 ◽  
Vol 119 (7) ◽  
pp. 3058-3062 ◽  
Author(s):  
Ronny Golnak ◽  
Jie Xiao ◽  
Kaan Atak ◽  
Munirah Khan ◽  
Edlira Suljoti ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Energy Gap ◽  
Local Energy ◽  
Gap Opening

Energy gap opening by crossing drop cast single-layer graphene nanoribbons

2018 ◽  
Vol 29 (31) ◽  
pp. 315705 ◽  
Author(s):  
Toyo Kazu Yamada ◽  
Hideto Fukuda ◽  
Taizo Fujiwara ◽  
Polin Liu ◽  
Kohji Nakamura ◽  
...  
Keyword(s):  
Energy Gap ◽  
Graphene Nanoribbons ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Layer Graphene ◽  
Gap Opening

scholarly journals Spin-polarized energy-gap opening in asymmetric bilayer graphene nanoribbons

2010 ◽  
Vol 97 (26) ◽  
pp. 263114 ◽  
Author(s):  
Gyubong Kim ◽  
Seung-Hoon Jhi
Keyword(s):  
Energy Gap ◽  
Graphene Nanoribbons ◽  
Bilayer Graphene ◽  
Spin Polarized ◽  
Gap Opening
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