Nb-Characterization

DFT

--Insert the name of the file associated to this phase of the characterization-- --Insert the required steps below and mark the ones that have been already completed-- --Insert the data extrapolated from the simulations--

AFM

--Insert the name of the file associated to this phase of the characterization-- --Insert the required steps below and mark the ones that have been already completed-- --Insert the data extrapolated from the analysis--

Resistivity

Resistivity and Mean Free Path

1. $\rho (T)$ via VDP technique. MORE DETAILED IN ./R-vs-T/readme.md
   • Iterative solution of the VDP equation from $R_{front}$ and $R_{back}$.
     • Filter data (we can try both methods):
     • Discard high $\Delta$T for $R_{front}$ and $R_{back}$.
     • Discard $R_{front}$ and $R_{back}$ corresponding to high T fluctuation.
   • Plot $\rho (T)$.
     • Merge proper datasets to obtain complete curve from 300k to 2.9k.
2. Condcutivity $\sigma (T)$
   • Through $n$ and $m^{*}$ from DFT.
   • Through $v_f$ and DOS from DFT.
     • In both cases one parameter is exact (n and DOS) and the other is approximated ($m^{*}$ and $v_f$).
   • Find $\tau$.
     • Not easy to compare $\tau$ with literature, so we find and discuss $l$ instead.
   • Ioffe-Regel parameter calculation: we want it greater than 1 amap.
     • Calculation explicitely requested for low T above Tc, suggested also for higher T.

Resistivity vs Temperature

1. RRR calculation
   • Discussion of RRR wrt thickness and mean free path. Comparison with literature.
2. Bloch Gruneisen Model FIT
   • Fundamental parameters: $\rho_0$, n, $\Theta_{BG}$.
     • We can let them free, but it's not easy to obtain proper fit.
     • We can set $\rho_0$ since we have it.
     • A way to determine n is to plot $ln(\rho - \rho_0)$ vs $ln(T)$. This plot will hae initial angular coefficient equal to n! But $\rho_0$ must be really precise.
   • The fit is always linear for high T.
   • Great focus on the scattering crossover (where the curve changes power)
     • If from the fit we get n=5 there are no big problems, material is quite good.
     • If we obtain something smaller than 5, we need to distinguish among different scattering mechanism, identifying which is the dominant one.
     • If $n \sim 2$, the material is strongly correlated.
   • From the A coefficient we determine $\lambda_{TR}$, to compare with DFT and literature.