scholarly journals Quasi-particle interference of the van Hove singularity in Sr2RuO4

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
A. Kreisel ◽  
C. A. Marques ◽  
L. C. Rhodes ◽  
X. Kong ◽  
T. Berlijn ◽  
...  
Keyword(s):  
Surface Layer ◽  
Fermi Energy ◽  
Singlet State ◽  
Wave Functions ◽  
Layered Compounds ◽  
Van Hove Singularity ◽  
Quasi Particle ◽  
Unconventional Superconductors ◽  
Structural Distortions ◽  
Topological Quantum

AbstractThe single-layered ruthenate Sr2RuO4 is one of the most enigmatic unconventional superconductors. While for many years it was thought to be the best candidate for a chiral p-wave superconducting ground state, desirable for topological quantum computations, recent experiments suggest a singlet state, ruling out the original p-wave scenario. The superconductivity as well as the properties of the multi-layered compounds of the ruthenate perovskites are strongly influenced by a van Hove singularity in proximity of the Fermi energy. Tiny structural distortions move the van Hove singularity across the Fermi energy with dramatic consequences for the physical properties. Here, we determine the electronic structure of the van Hove singularity in the surface layer of Sr2RuO4 by quasi-particle interference imaging. We trace its dispersion and demonstrate from a model calculation accounting for the full vacuum overlap of the wave functions that its detection is facilitated through the octahedral rotations in the surface layer.

Structural distortions in the surface layer of single-crystal molybdenum after face grinding

1998 ◽  
Vol 37 (5-6) ◽  
pp. 336-342 ◽  
Author(s):  
A. A. Adamovskii ◽  
D. V. Lotsko ◽  
T. V. Chernenko
Keyword(s):  
Surface Layer ◽  
Single Crystal ◽  
Structural Distortions ◽  
Face Grinding

EPR Elements of Physical Reality in Quantum Mechanics

1997 ◽  
Vol 12 (29) ◽  
pp. 5289-5303
Author(s):  
V. K. Thankappan ◽  
Ravi K. Menon
Keyword(s):  
Wave Function ◽  
Quantum Mechanics ◽  
Singlet State ◽  
Physical Reality ◽  
The State ◽  
Wave Functions ◽  
Definition Of

The concept of elements of physical reality (e.p.r.) in quantum mechanics as defined by Einstein, Podolsky and Rosen (EPR) is discussed in the context of the EPR–Bohm and the EPR–Bell experiments on a pair of spin 1/2 particles in the singlet state. It is argued that EPR's definition of e.p.r. is appropriate to the EPR–Bell experiment rather than to the EPR–Bohm experiment, and that Bohr's interpretation of e.p.r. is also consistent with such a viewpoint. It is shown that the observed correlation between the spins of the two particles in the EPR–Bell experiment is just a manifestation of the correlation that exists between the wave functions of the particles in the singlet state and a consequence of the fact that a Stern–Gerlach magnet does not change the state of a particle but only transforms its wave function into a representation defined by the axis of the magnet. As such, the correlation is suggested to be an affirmation of Einstein's concept of locality, and not an evidence for nonlocality.

scholarly journals Moiréless correlations in ABCA graphene

2021 ◽  
Vol 118 (4) ◽  
pp. e2017366118 ◽  
Author(s):  
Alexander Kerelsky ◽  
Carmen Rubio-Verdú ◽  
Lede Xian ◽  
Dante M. Kennes ◽  
Dorri Halbertal ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Van Der Waals ◽  
Bilayer Graphene ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Van Hove Singularity ◽  
Natural Interfaces ◽  
Simple Material ◽  
Electronic Band ◽  
Topological Quantum

Atomically thin van der Waals materials stacked with an interlayer twist have proven to be an excellent platform toward achieving gate-tunable correlated phenomena linked to the formation of flat electronic bands. In this work we demonstrate the formation of emergent correlated phases in multilayer rhombohedral graphene––a simple material that also exhibits a flat electronic band edge but without the need of having a moiré superlattice induced by twisted van der Waals layers. We show that two layers of bilayer graphene that are twisted by an arbitrary tiny angle host large (micrometer-scale) regions of uniform rhombohedral four-layer (ABCA) graphene that can be independently studied. Scanning tunneling spectroscopy reveals that ABCA graphene hosts an unprecedentedly sharp van Hove singularity of 3–5-meV half-width. We demonstrate that when this van Hove singularity straddles the Fermi level, a correlated many-body gap emerges with peak-to-peak value of 9.5 meV at charge neutrality. Mean-field theoretical calculations for model with short-ranged interactions indicate that two primary candidates for the appearance of this broken symmetry state are a charge-transfer excitonic insulator and a ferrimagnet. Finally, we show that ABCA graphene hosts surface topological helical edge states at natural interfaces with ABAB graphene which can be turned on and off with gate voltage, implying that small-angle twisted double-bilayer graphene is an ideal programmable topological quantum material.

scholarly journals THE GRAPH-REPRESENTATION APPROACH TO TOPOLOGICAL FIELD THEORY IN 2 + 1 DIMENSIONS

1992 ◽  
Vol 07 (03) ◽  
pp. 563-589
Author(s):  
STEPHEN P. MARTIN
Keyword(s):  
Field Theory ◽  
Poisson Bracket ◽  
Wave Functions ◽  
Graph Representation ◽  
Commutator Algebra ◽  
Gauge Transformations ◽  
Topological Quantum ◽  
Topological Field ◽  
Definition Of ◽  
Theory Of Graphs

An alternative definition of topological quantum field theory in 2 + 1 dimensions is discussed. The fundamental objects in this approach are not gauge fields as in the usual approach, but nonlocal observables associated with graphs. The classical theory of graphs is defined by postulating a simple diagrammatic rule for computing the Poisson bracket of any two graphs. The theory is quantized by exhibiting a quantum deformation of the classical Poisson-bracket algebra, which is realized as a commutator algebra on a Hilbert space of states. The wave functions in this "graph representation" approach are functionals on an appropriate set of graphs. This is in contrast to the usual "connection representation" approach, in which the theory is defined in terms of a gauge field and the wave functions are functionals on the space of flat spatial connections modulo gauge transformations.

scholarly journals Neutral current neutrino-94Mo scattering in the context of the QRPA method

2019 ◽  
Vol 18 ◽  
pp. 31
Author(s):  
K. G. Balasi ◽  
T. S. Kosmas
Keyword(s):  
Cross Sections ◽  
Random Phase Approximation ◽  
Neutral Current ◽  
Random Phase ◽  
Reaction Rates ◽  
Systematic Investigation ◽  
Wave Functions ◽  
Phase Approximation ◽  
Quasi Particle ◽  
Intermediate Energies

A systematic investigation of neutrino-nucleus reaction rates at low and intermediate energies of the stable 94Mo isotope is performed. Differential and integrated cross sections for neutrino inelastic scattering off the aforementioned target are calculated for neutrino energies εi ≼ 100 MeV. The nuclear wave functions for the initial and final nuclear states are constructed in the context of the quasi-particle random phase approximation (QRPA). The reliability of our method is tested by checking the reproducibility of the low-lying energy spectrum of the isotope under investigation.

Conductivity of Grown Germanium-Bicrystals

1959 ◽  
Vol 14 (3) ◽  
pp. 281-284
Author(s):  
H. F. Mataré ◽  
B. Reed ◽  
O. A. Weinreich
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Grain Boundary ◽  
Internal Surface ◽  
Wave Functions ◽  
Leakage Currents ◽  
Layer Width ◽  
Temperature Range ◽  
Conductivity Mechanism ◽  
Boundary Conduction

Measurements of the grain boundary conduction in Ge-bicrystals grown from material of widely different impurity ranges show sheet resistivities of .003 to .01 ohm-cm for an assumed grain boundary layer width of 100 A. This value is practically constant throughout a temperature range from 2 °K to 300°K if leakage currents through the bulk are kept small by the use of junction contacts. This and the linear I—V characteristic suggest that the conductivity mechanism is dominated by the free orbitals and their overlapping wave functions in the internal surface layer.

scholarly journals Nematic fluctuations in the cuprate superconductor Bi2Sr2CaCu2O8+δ

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
N. Auvray ◽  
B. Loret ◽  
S. Benhabib ◽  
M. Cazayous ◽  
R. D. Zhong ◽  
...  
Keyword(s):  
Critical Point ◽  
Quantum Critical Point ◽  
Van Hove Singularity ◽  
Superconducting Cuprates ◽  
Unconventional Superconductors ◽  
Pseudogap Phase ◽  
Electronic Raman Scattering ◽  
Quantum Critical ◽  
Canonical Quantum ◽  
Metal Phases

AbstractEstablishing the presence and the nature of a quantum critical point in their phase diagram is a central enigma of the high-temperature superconducting cuprates. It could explain their pseudogap and strange metal phases, and ultimately their high superconducting temperatures. Yet, while solid evidences exist in several unconventional superconductors of ubiquitous critical fluctuations associated to a quantum critical point, in the cuprates they remain undetected until now. Here using symmetry-resolved electronic Raman scattering in the cuprate $${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta}$$Bi2Sr2CaCu2O8+δ, we report the observation of enhanced electronic nematic fluctuations near the endpoint of the pseudogap phase. While our data hint at the possible presence of an incipient nematic quantum critical point, the doping dependence of the nematic fluctuations deviates significantly from a canonical quantum critical scenario. The observed nematic instability rather appears to be tied to the presence of a van Hove singularity in the band structure.

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