2000年度 第26回
下記の通りコロキウムを企画致しました。講演者の方には、学生や分野の違う方にもわかるレベルから始めて下さるようにお願いしてあります。是非ともご参加下さいますよう、ご案内申し上げます。
なお、今後の予定については www.phys.aoyama.ac.jp/seminars/
を御覧下さい。 また理工学部キャンパスへの交通についてはwww.phys.aoyama.ac.jp/maps/を御覧下さい。
講演者:Prof. D.M. Edwards (Imperial College, London)
日時: 10月27日(金) 午後4時半から
場所: 青山学院大学 理工学部(世田谷キャンパス) 一号館 5階 1538号室
講演題目: Ferromagnetism and Transport in the Double Exchange Model, with and without Phonons
要旨:
Recently the observed colossal magnetoresistance in manganites has caused
attention to be focussed on the so-called double exchange (DE) model of
these materials. In this s-d model electrons in a conduction band interact
with local manganese spins and, in the more general Holstein-DE model,
with local phonons. In the classical limit for the local spins and phonons
these models are one-electron problems which can be solved almost
analytically within the approximation of dynamical mean field
theory (DMFT). The standard coherent potential approximation (CPA) is
equivalent to DMFT for these one-electron problems. For the many-body
case of quantum local spins and phonons, where DMFT is intractable
analytically, we have developed a many-body CPA which is exact in the
atomic limit and reduces to DMFT in the classical limit. We use our CPA
to discuss quantum effects on the electronic spectrum, Curie temperature
and resistivity, comparing our results with experimental results on
manganites. Good semi-quantitative agreement is obtained for the
temperature and field dependence of the resistivity.
共催・青山学院大学 理工学会 物理学分科会