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.

NEUTRAL EXCITATIONS IN QUASI-1D STRONGLY CORRELATED ELECTRON SYSTEMS

1989 ◽  
Vol 03 (12) ◽  
pp. 2159-2168 ◽  
Author(s):  
D.J. Klein ◽  
M.A. García-Bach ◽  
R. Valentí
Keyword(s):  
Energy Gap ◽  
Visible Region ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Strongly Correlated Electron ◽  
Quasi Particle ◽  
Correlated Electron Systems ◽  
Correlated Electron ◽  
Site Cluster ◽  
Electron Correlation Effects

Novel neutral spin-0 excitations for quasi-1D systems with one electron per site are obtained within a localized scheme. Our ground state wave-function is defined by a variational localized - site cluster - expanded ansatz and these excitations are naturally built upon it. All computations are easily carried out by a transfer matrix technique that enables explicit inclusion of electron - correlation effects and, at the same time, provides a quasi—particle band—theoretic picture of these excitations. This treatment is applied, in particular, to a polyphene strip. At k=0 the energy gap corresponds to a dipole-allowed transition in the visible region, our result compares fairly well with observed decreasing transitions for finite polyphene strips.

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.

EXACTNESS OF FERMIONIC LINEARIZATION SCHEME WITH CLIFFORD VARIABLES IN d=∞

1995 ◽  
Vol 09 (16) ◽  
pp. 971-975 ◽  
Author(s):  
ARIANNA MONTORSI
Keyword(s):  
Exact Solution ◽  
Single Site ◽  
Strongly Correlated Electron Systems ◽  
Strongly Correlated ◽  
Electron Systems ◽  
Strongly Correlated Electron ◽  
Correlated Electron Systems ◽  
Correlated Electron

We show that the fermionic linearization scheme for dealing with strongly correlated electron systems — when implemented with Clifford variables — becomes exact in the d=∞ limit, at least for Hubbard-like models. In this case, the model is mapped exactly into a single-site problem. The conditions under which such a feature allows to obtain an exact solution are also discussed.

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