Research in the Gweon Group
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| ARPES researchers in high temperature superconductors have not figured out yet how to analyze the ARPES data ''wholly'' as a two dimensional function $A(k,\omega)$, a function of $k$ and $\omega$, for technical reasons. Instead, researchers study EDCs (EDC is an energy distribution curve given by $A(k,\omega)$ at a fixed $k$ value) or MDCs (MDC is a momentum distribution curve given by $A(k,\omega)$ at a fixed $\omega$ value), ''separately.'' | ARPES researchers in high temperature superconductors have not figured out yet how to analyze the ARPES data ''wholly'' as a two dimensional function $A(k,\omega)$, a function of $k$ and $\omega$. Why not? The reasons are both technical and physical. At this point, it suffices to note that researchers analyze EDCs (EDC is an energy distribution curve given by $A(k,\omega)$ at a fixed $k$ value) or MDCs (MDC is a momentum distribution curve given by $A(k,\omega)$ at a fixed $\omega$ value) ''separately.'' |
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| It turns out that in [[sECFL|our initial work]], we could describe EDCs but not MDCs. In this work, for the first time, we have shown that it is possible to described EDCs and MDCs of high tempearture superconductors on equal footing using a miscropically based model. This is an unprecedented achievement. For this, we had to modify the original ECFL model (“simple ECFL”) in a phenomenological way to make this work: the resulting model is thus called the pheonmenological ECFL (pECFL) model. | It turns out that in [[sECFL|our initial work]], we could describe EDCs but not MDCs. This was what was wanting from an experimentalist's point of view. So, I embarked on improving the model. I came up with ccouple of ideas that worked. In this work, for the first time, we have shown that it is possible to described EDCs and MDCs of high tempearture superconductors on equal footing using a miscropically based model. This is an unprecedented achievement. For this, we had to modify the original ECFL model (“simple ECFL”) in a phenomenological way to make this work: the resulting model is thus called the pheonmenological ECFL (pECFL) model. |
Phenomenological ECFL
We had success in explaining the ARPES data using the so-called “simple” extremely correlated Fermi liquid (sECFL) theory.
However, from an experimentalist's point of view, this work had something still wanting. Why? To explain, let us note that the ARPES data give the single-particle spectral function $A(k, \omega)$, where $\hbar k$ is the momentum and $\hbar \omega$ is the negative energy of the electronic state measured. In ARPES, the data corresponding to the momentum along one direction (“cut”) is obtained as one unit of data. So, $\hbar k$ gives the momentum value along a given ARPES cut.
EDCs and MDCs
ARPES researchers in high temperature superconductors have not figured out yet how to analyze the ARPES data wholly as a two dimensional function $A(k,\omega)$, a function of $k$ and $\omega$. Why not? The reasons are both technical and physical. At this point, it suffices to note that researchers analyze EDCs (EDC is an energy distribution curve given by $A(k,\omega)$ at a fixed $k$ value) or MDCs (MDC is a momentum distribution curve given by $A(k,\omega)$ at a fixed $\omega$ value) separately.
When ARPES was applied to high temperature superconductors initially, researchers forcused on EDCs, as the EDC is commonly viewed as more fundamental for good reasons. However since around 2000, ARPES researchers fell in love with MDCs, due to the practical reason that MDCs are easier to analyze. And, it seemed that they give useful information, if one makes certain assumptions such as the momentum-independent Dyson self energy.
pECFL does it all
It turns out that in our initial work, we could describe EDCs but not MDCs. This was what was wanting from an experimentalist's point of view. So, I embarked on improving the model. I came up with ccouple of ideas that worked. In this work, for the first time, we have shown that it is possible to described EDCs and MDCs of high tempearture superconductors on equal footing using a miscropically based model. This is an unprecedented achievement. For this, we had to modify the original ECFL model (“simple ECFL”) in a phenomenological way to make this work: the resulting model is thus called the pheonmenological ECFL (pECFL) model.
What does it mean?
Quite pleasantly, we find, through our very comprehensive experimental work, that this phenomenological change is actually quite important: it seems to connect nicely to features that are related to the superconductivity itself! Follow the links below, to learn more about this emerging picture.