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diff --git a/Jauslin_Hagedornfest_2019.tex b/Jauslin_Hagedornfest_2019.tex new file mode 100644 index 0000000..c81be67 --- /dev/null +++ b/Jauslin_Hagedornfest_2019.tex @@ -0,0 +1,288 @@ +\documentclass{ian-presentation} + +\usepackage[hidelinks]{hyperref} +\usepackage{graphicx} +\usepackage{array} + +\begin{document} +\pagestyle{empty} +\hbox{}\vfil +\bf\Large +\hfil Time-evolution of electron emission\par +\smallskip +\hfil from a metal surface\par +\vfil +\large +\hfil Ian Jauslin +\normalsize +\vfil +\hfil\rm joint with {\bf Ovidiu Costin}, {\bf Rodica Costin}, and {\bf Joel L. Lebowitz}\par +\vfil +arXiv:{\tt \href{http://arxiv.org/abs/1808.00936}{1808.00936}}\hfill{\tt \href{http://ian.jauslin.org}{http://ian.jauslin.org}} +\eject + +\setcounter{page}1 +\pagestyle{plain} + +\title{Field emission} +\vfill +\hfil\includegraphics[height=5cm]{emitter.jpg} +\vfill +\eject + +\title{Field emission} +$$ + V(x)=U\Theta(x) + ,\quad + E_{\mathrm F}=k_{\mathrm F}^2<U +$$ +\hfil\includegraphics[height=5cm]{potential_square.pdf} +\vfill +\eject + +\title{Thermal emission} +$$ + V(x)=U\Theta(x) + ,\quad + k^2>U +$$ +\hfil\includegraphics[height=5cm]{potential_square_thermal.pdf} +\vfill +\eject + +\title{Photonic emission} +$$ + V_t(x)=\Theta(x)(U-E_tx) + ,\quad + E_t=2\epsilon\omega\cos(\omega t) +$$ +\hfil\includegraphics[height=5cm]{potential_square_photonic.pdf} +\vfill +\eject + +\title{Field emission} +$$ + V(x)=\Theta(x)(U-Ex) +$$ +\hfil\includegraphics[height=5cm]{potential.pdf} +\vfill +\eject + +\title{Field emission} +\begin{itemize} + \item \href{https://doi.org/10.1073\%2Fpnas.14.1.45}{[Millikan, Lauritsen, 1928]}: experimental plot of the logarithm of the current against $1/E$ +\end{itemize} +\hfil\includegraphics[height=4.5cm]{Millikan-Lauritsen_current.png} +\vfill +\eject + +\title{Field emission through a triangular barrier} +\vfill +\begin{itemize} + \item \href{https://doi.org/10.1098/rspa.1928.0091}{[Fowler, Nordheim, 1928]}: predicted that the current is, for small $E$, + $$ + J\approx CE^2e^{-\frac aE} + $$ + \item (\href{https://doi.org/10.1088/1751-8113/44/5/05530@}{[Rokhlenko, 2011]}: studied the range of applicability of the approximation, and found more accurate approximations for larger fields.) +\end{itemize} +\vfill +\eject + +\title{Fowler-Nordheim equation} +\begin{itemize} + \item Schr\"odinger equation + $$ + i\partial_t\psi=-\Delta\psi+\Theta(x)(U-Ex)\psi + $$ + \item Fowler-Nordheim: stationary solution: $\psi_{\mathrm{FN}}(x,t)=e^{-ik^2t}\varphi_{\mathrm{FN}}(x)$ + $$ + \varphi_{\mathrm{FN}}(x)= + \left\{ \begin{array}{l@{\ }l} + e^{ikx}+R_Ee^{-ikx} & x<0\\ + T_E\mathrm{Ai}(e^{-\frac{i\pi}3}(E^{\frac13}x-E^{-\frac23}(U-k^2)) & x>0 + \end{array}\right. + $$ + $R_E$ and $T_E$ are chosen so that $\varphi_{\mathrm{FN}}$ and $\partial\varphi_{\mathrm{FN}}$ are continuous at $x=0$. +\end{itemize} +\vfill +\eject + +\title{Fowler-Nordheim equation} +\vfill +\hfil\includegraphics[height=5.5cm]{asymptotic.pdf} +\vfill +\eject + +\title{Initial value problem} +\begin{itemize} + \item Initial condition: + $$ + \psi(x,0)= + \left\{ \begin{array}{l@{\ }l} + e^{ikx}+R_0e^{-ikx} & x<0\\ + T_0 e^{-\sqrt{U-k^2}x} & x>0 + \end{array}\right. + $$ + $R_0$ and $T_0$ ensure that $\psi$ and $\partial\psi$ are continuous. + \item {\bf Theorem}: $\psi(x,t)$ behaves asymptotically like $\psi_{\mathrm{FN}}$: + $$ + \psi(x,t) + =\psi_{\mathrm{FN}}(x,t)+\left(\frac{t}{\tau_E(x)}\right)^{-\frac32}+O(t^{-\frac52}) + . + $$ +\end{itemize} +\vfill +\eject + +\title{Photoemission} +\begin{itemize} + \item Photoelectric effect: early observations: \href{https://doi.org/10.1002/andp.18872670827}{[Hertz, 1887]}, \href{https://doi.org/10.1002/andp.18882690206}{[Hallwachs, 1888]}, \href{https://doi.org/10.1002/andp.19003070611}{[Lenard, 1900]}. + \item When a metal is irradiated with ultra-violet light, electrons are ionized, with kinetic energies at integer multiples of $\hbar\omega$. + \item \href{https://doi.org/10.1002/andp.19053220607}{[Einstein, 1905]}: interpretation: quanta of light ({\it photons}) of energy $\hbar\omega$ are absorbed by the electrons, whose kinetic energy is raised by $n\hbar\omega$, and can escape the metal. +\end{itemize} +\vfill +\eject + +\title{Photoemission} +\begin{itemize} + \item Time dependent potential: + $$ + V_t(x)=\Theta(x)(U-2\epsilon\omega\cos(\omega t)x) + $$ + \item Magnetic gauge: + $$ + \Psi(x,t) + :=\psi(x,t)e^{-ix\Theta(x)A(t)} + ,\quad + A(t):=\int_0^t ds\ 2\epsilon\omega\cos(\omega s) + = + 2\epsilon\sin(\omega t) + $$ + satisfies + $$ + i\partial_t\Psi(x,t)=\left((-i\nabla+\Theta(x)A(t))^2+\Theta(x)U\right)\Psi(x,t) + $$ +\end{itemize} +\vfill +\eject + +\title{Periodic solution} +\vskip-10pt +\begin{itemize} + \item \href{https://doi.org/10.1103/PhysRevA.72.023412}{[Faisal, Kami\'nski, Saczuk, 2005]} + $$ + \Psi_{\mathrm{FKS}}(x,t)=\left\{\begin{array}{ll} + e^{ikx}\exp\left(-ik^2t\right)+\Psi_R(x,t)&\mathrm{\ if\ }x<0\\ + \Psi_T(x,t)&\mathrm{\ if\ }x>0 + \end{array}\right. + $$ + $$ + \Psi_R(x,t)=\sum_{M\in\mathbb Z}R_Me^{-iq_Mx}\exp\left(-iq_M^2t\right) + ,\quad + q_M=\sqrt{k^2+M\omega} + $$ + $$ + \Psi_T(x,t)=\sum_{M\in\mathbb Z}T_Me^{ip_Mx}\exp\left(-iUt-i\int_0^td\tau\ (p_M-A(\tau))^2\right) + $$ + $$ + p_M=\sqrt{k^2-U+M\omega-2\epsilon^2} + $$ + \item $\Psi(x,t)$, $(-i\nabla+\Theta(x)A(t))\Psi(x,t)$ are continuous. +\end{itemize} +\vfill +\eject + +\title{Initial value problem} +\begin{itemize} + \item Initial condition: + $$ + \Psi(x,0)= + \left\{ \begin{array}{l@{\ }l} + e^{ikx}+R_0e^{-ikx} & x<0\\ + T_0 e^{-\sqrt{U-k^2}x} & x>0 + \end{array}\right. + $$ + $R_0$ and $T_0$ ensure that $\Psi$ and $\partial\Psi$ are continuous. + \item {\bf Conjecture} (in progress): $\Psi(x,t)$ behaves asymptotically like $\Psi_{\mathrm{FKS}}$: + $$ + \psi(x,t) + =\psi_{\mathrm{FKS}}(x,t)+\left(\frac{t}{\tau_{\mathrm{FKS}}(x)}\right)^{-\frac32}+O(t^{-\frac52}) + . + $$ +\end{itemize} +\vfill +\eject + +\title{Idea of the proof: field emission} +\begin{itemize} + \item Laplace transform: + $$ + \hat\psi_p(x):=\int_0^\infty dt\ e^{-pt}\psi(x,t) + $$ + \item Schr\"odinger equation: + $$ + (-\Delta+\Theta(x)V(x)-ip)\psi_p(x)=-i\psi(x,0) + ,\quad + V(x):=U-Ex + $$ +\end{itemize} +\vfill +\eject + +\title{Solution in Laplace space} +\begin{itemize} + \item For simplicity, $R_0\equiv T_0\equiv0$. + \item Solution: + $$ + \hat\psi_p(x)= + \left\{\begin{array}{>\displaystyle l@{\ }l} + c(p)e^{\sqrt{-ip}x}-\frac{ie^{ikx}}{-ip+k^2} + &\mathrm{if\ }x<0\\[0.5cm] + d(p)\varphi_p(x) + &\mathrm{if\ }x> 0 + \end{array}\right. + $$ + with + $$ + (-\Delta+V(x)-ip)\varphi_p(x)=0 + $$ + $$ + \varphi_p(x)=\mathrm{Ai}\left(e^{-\frac{i\pi}3}\left(E^{\frac13}x-E^{-\frac23}(U-ip)\right)\right) + $$ +\end{itemize} +\vfill +\eject + +\title{Solution in Laplace space} +\begin{itemize} + \item $c$ and $d$ ensure that $\hat\psi_p(x)$ and $\partial\hat\psi_p(x)$ are continuous at $x=0$: + $$ + c(p)=\frac{i(ik\varphi_p(0)-\partial\varphi_p(0))}{(-ip+k^2)(\sqrt{-ip}\varphi_p(0)-\partial\varphi_p(0))} + $$ + $$ + d(p)=-\frac{i}{(\sqrt{-ip}+ik)(\sqrt{-ip}\varphi_p(0)-\partial\varphi_p(0))}. + $$ +\end{itemize} +\vfill +\eject + +\title{Poles in Laplace plane} +\vfill +\hfil\includegraphics[height=5.5cm]{contour.pdf} +\vfill +\eject + +\title{Asymptotic behavior} +\begin{itemize} + \item As $t\to\infty$: + $$ + \psi(x,t) + =\psi_{\mathrm{FN}}(x,t)+\left(\frac{t}{\tau_E(x)}\right)^{-\frac32}+O(t^{-\frac52}) + . + $$ + + \item If $k<0$ (reflected wave), then there is no pole on the imaginary axis, so there is no contribution as $t\to\infty$. + \item Similarly, the transmitted wave in the initial condition does not contribute. +\end{itemize} + +\end{document} |