Electron Tunneling Studies of Variable Range Hopping Conductors

技术摘要：许多仅在金属绝缘体过渡的绝缘侧的材料通过可变跳程（VRH）导电，其电导率取决于温度，为exp(T0/T)1/n，对于整数n 1。虽然非相互作用电子的VRH被很好地理解，但最近的实验表明，低温下存在磁扰动的VRH会导致新的和意想不到的现象，包括新的自旋-电荷耦合准粒子的可能性。计划利用低温高磁场下的电子隧穿和磁输运实验研究VRH导体的多体态密度和初等激发谱。目的是直接测量由电导率数据推断出的能隙结构，并阐明磁散射对跳变传导的影响。摘要：凝聚态物理的一个基本问题是固体中的导电机制。虽然对普通金属和半导体的理解高度发达，但许多材料表现出不寻常的，通常难以理解的电学行为。一种常见的非常规导电形式被称为变程跳变（VRH）。由于许多不同的技术上重要的固体都是VRH导体，因此对这一过程进行更深刻的物理理解具有实际意义。最近的实验表明，VRH传导可以产生复杂的和完全意想不到的行为。为了阐明这种导电行为的基本原理，提出直接研究不同VRH导体中载流子的微观性质。＊＊＊

9316803 Lee Technical abstract: Many materials that are barely on the insulating side of a metal-insulator transition conduct electricity by variable range hopping (VRH), for which the conductivity depends on temperature as exp(T0/T)1/n, for integer n 1. While VRH by non-interacting electrons is well understood, recent experiments have shown that VRH at low temperatures in the presence of magnetic perturbations leads to new and unexpected phenomena, including the possibility of a new spin-charge coupled quasiparticle. It is planned to investigate the many-body density-of-states and elementary excitation spectrum in VRH conductors using electron tunneling and magneto transport experiments at low temperatures and high magnetic fields. The goal is to directly measure the proposed energy gap structure inferred from conductivity data and to elucidate the effects of magnetic scattering on hopping conduction. Non-technical abstract: A fundamental problem in condensed matter physics is concerned with the mechanism of electrical conduction in a solid. While the understanding of common metals and semiconductors is highly developed, many materials exhibit unusual, often poorly understood electrical behavior. A commonly observed form of unconventional electrical conduction is known as variable- range hopping (VRH). Since many diverse technologically important solids are VRH conductors, it is of practical importance to develop a more profound physical understanding of this process. Recent experiments have shown that VRH conduction can yield complex and completely unexpected behavior. In order to elucidate the fundamental principles which underlie this electrical conductiom it is proposed to study directly rhe microscopic properties of the charge carriers in different VRH conductors. ***