ar X iv : c on d - m at / 9 70 80 28 v 2 6 J an 1 99 8 Local polariton states in impure ionic crystals

X iv : c on d - m at / 9 70 80 28 v 1 4 A ug 1 99 7 Local polariton states in impure ionic crystals

We consider dynamics of an ionic crystal with a single impurity in the vicinity of the polariton resonance. We show that if the polariton spectrum of the host crystal allows for a gap between polariton branches, the defect gives rise to a novel kind of local states with frequencies within the gap. Despite the atomic size of the impurity we find that new local states are predominated by long wav...

ar X iv : c on d - m at / 9 70 30 28 v 1 3 M ar 1 99 7 In - plane optical response of Bi 2 Sr 2 CuO 6

We report on infrared reflectivity measurements of the ab-plane response of superconducting Bi2Sr2CuO6 single crystals. The frequency dependent conductivity has a maximum near 500 cm at room temperature, which shifts to lower frequency and merges with a Drude peak below 100 K. We attribute the unusual behavior of the mid-infrared conductivity to low frequency transitions between electronic band...

ar X iv : c on d - m at / 9 61 21 37 v 1 1 4 D ec 1 99 6 A complete devil ’ s staircase in the Falicov - Kimball model

In this letter we study the ground-state phase diagram of the one-dimensional Falicov-Kimball model. This model was proposed to describe metal-insulator transitions [ 1] and has since been investigated in connection with a variety of problems such as binary alloys [ 2], ordering in mixed-valence systems [ 3], and the formation of ionic crystals [ 4]. It is the latter language we shall use here,...

ar X iv : h ep - l at / 9 80 70 28 v 1 1 1 Ju l 1 99 8 COURSE INTRODUCTION TO LATTICE QCD

ar X iv : c on d - m at / 9 80 60 82 v 1 [ co nd - m at . m tr l - sc i ] 5 J un 1 99 8 Magnetic Particles