Observation of competing, correlated ground states in the flat band of rhombohedral graphite
Zoltán Tajkov
Nanostructures Department, Centre for Energy Research,
Department of Biological Physics, Eötvös Loránd University
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Electrons in solids - Band theory
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\left[ -\frac{\hbar^2}{2m}\nabla^2 + U\left( \mathbf{r} \right) \right] \psi\left( \mathbf{r} \right) = \varepsilon \psi\left( \mathbf{r} \right)
averaged potential
Electrons in solids - Band theory
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\left[ -\frac{\hbar^2}{2m}\nabla^2 + U\left( \mathbf{r} \right) \right] \psi\left( \mathbf{r} \right) = \varepsilon \psi\left( \mathbf{r} \right)
Why do we use it?
- electrical resistivity
- optical absorption
- foundation of solid-state electronics
It explains...
Electrons in solids - Beyond band theory
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Why do we use it?
Because we can.
An example: methane
1 carbon atom + 4 hydrogen atoms = 10 electrons
30 independent coordinates
100 points per coordinate
\( 100^{30}=10^{60} \) complex number
1 complex number in every atom
We can store the wave function in \( 10^{30} m^3 \)
Strongly correlated electron systems
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- Colossal magnetoresistance
- High-temperature superconductivity
- VO\( _2 \)
Elbio Dagotto, Science 309, 257 (2005)
Rhombohedral Graphite
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E(\mathbf{q}) \propto |\mathbf{q}|^N
SSH chain
Rhombohedral Graphite
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What does the experiment say? STM results
Rhombohedral Graphite
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DMRG - Beyond meanfield
Theory
Degenerate ground state!
Rhombohedral Graphite
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Experiments
Rhombohedral Graphite
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The team
Oroszlányi László
Koltai János
Hagymási Imre
Nemes-Incze Péter
Péter Vancsó
András Pálinkás
Levente Tapasztó
Rhombohedral Graphite
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\( \mu_1 \approx 10^{-2} \mu_\mathrm{Bohr} \)
LDA+U vs LDA, meanfield
Possible explanations I.
Rhombohedral Graphite
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External electric field
Possible explanations II.
E-field strength 0.05 V/Å
Rhombohedral Graphite
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Quantum confinement
Possible explanations III.
Rhombohedral Graphite
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Experiments - one more thing
Symmetry breaking
DOFFI 2021
By novidad21
