Research in the Gweon Group
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| ARPES is a recognized main tool for studying many body interactions in cuprates (and other hot materials such as graphene and topological insulators). Here at UCSC, we have taken some unique data for the past few years. The unique data that we have obtained at the SSRL (Stanford) and the ALS (Berkeley) have led to the discovery of a new anomaly in ARPES. This is a new anomaly, since it is experimentally quite distinct from the two anomalies the field is already quite familiar with (the low energy dispersion anomaly and the high energy dispersion anomaly; dispersion anomaly = “kink” in common ARPES lingo). | ARPES is a recognized main tool for studying many body interactions in cuprates (and other hot materials such as graphene and topological insulators). Here at UCSC, we have taken some unique data for the past few years. The unique data that we have obtained at the SSRL (Stanford) and the ALS (Berkeley) have led to the discovery of a new anomaly in ARPES. This is a new anomaly, since it is experimentally quite distinct from the two anomalies the field is already quite familiar with: the low energy dispersion anomaly and the high energy dispersion anomaly; dispersion anomaly = “kink” in common ARPES lingo. |
Anomalous nodal many body density of states
The density of states (DOS) is a basic quantity, e.g., for describing free electrons in a solid. The electron DOS says how many electrons the material can accommodate at a certain energy value.
In a strongly correlated electron system such as high temperature superconductors, the equivalent quantity is the many body density of states (MBDOS), $\int d\vec k A(\vec k, \omega)$, where $A$ is the single particle spectral function, measured by ARPES. Even when the DOS is predicted to be finite at the Fermi energy (“band metal”), strong correlation can lead to a vanishing MBDOS (“Mott-Hubbard insulator”).
A very important question that has been very tough to answer so far is “does the Mott insulator physics have a distinctive signature for a nearly optimally doped high temperature superconductor?”
The nMBDOS anomaly
ARPES is a recognized main tool for studying many body interactions in cuprates (and other hot materials such as graphene and topological insulators). Here at UCSC, we have taken some unique data for the past few years. The unique data that we have obtained at the SSRL (Stanford) and the ALS (Berkeley) have led to the discovery of a new anomaly in ARPES. This is a new anomaly, since it is experimentally quite distinct from the two anomalies the field is already quite familiar with: the low energy dispersion anomaly and the high energy dispersion anomaly; dispersion anomaly = “kink” in common ARPES lingo.
The nMBDOS anomaly, discovered here at UC Santa Cruz, is new and imply that the following two ingredients are important for the theory of high temperature superconductors: electron-hole asymmetry and k-dependent Dyson self energy.
What does the nMBDOS anomaly mean?
The Mott insulator physics is important for an extended doping range around the optimal doping. It also shows that the phenomenological modification introduced for the simple ECFL model may be important for the superconductivity. For details, please read the manuscript.
Links, data
- All ARPES data obtained in this paper were obtained by GHG at the SSRL, through many many days and nights of blissful experiments, in the past few years.