Density‐matrix theory of quantum dynamics under a strong external field switched on nonadiabatically. Issue 22 (10th June 2014)

• Record Type: Journal Article
• Authors: Kitamura, H.
• Is Part Of: International journal of quantum chemistry. Volume 114:Issue 22(2014:Nov. 15)
• Page Start: 1518
• Page End: 1527
• Publication Date: 2014-06-10
• Subjects: Quantum chemistry -- Periodicals; 541.28
• DOI: 10.1002/qua.24718
• Languages: English
• ISSNs: 0020-7608

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Quantum time‐evolution equations for the density matrix are formulated in the unrestricted Hartree–Fock approximation, with an emphasis on the nonperturbative effect due to a sudden or gradual onset of a strong external field. Numerical simulations are performed for ideal Fermi gas around a square‐well potential which is switched on dynamically. When the switching is fast enough, an oscillatory motion of the particle is induced by a nonadiabatic transition at the Landau–Zener crossing point, which is most clearly seen in a small‐size system. When the switching is sufficiently slow, the simulation corroborates the adiabatic theorem. It is shown that the Anderson's infrared catastrophe in a metal is strongly enhanced by the nonperturbative effect. The Keldysh formula of atomic multiphoton ionization can also be derived from the nonperturbative term in the density‐matrix equation, indicating a wide applicability of the present theory. © 2014 Wiley Periodicals, Inc.</p> </abstract>