Electron Tunneling Studies of Variable Range Hopping Conductors

9316803李技术摘要：许多不在金属-绝缘体转变绝缘一侧的材料通过可变范围跳跃导电，对于整数n 1，电导率与温度的关系为exp(T0/T)1/n。虽然人们熟知非相互作用电子的可变范围跳跃导电，但最近的实验表明，在存在磁扰动的低温下，可变范围跳跃导致了新的和意想不到的现象，包括可能出现新的自旋-电荷耦合准粒子。利用低温强磁场下的电子隧穿和磁输运实验研究了VRH导体的多体密度态密度和基元激发谱。其目的是直接测量从电导数据推断出的能隙结构，并阐明磁散射对跳跃导电的影响。非技术摘要：凝聚态物理中的一个基本问题是关于固体中的导电机制。虽然对常见金属和半导体的了解非常发达，但许多材料表现出不同寻常的、往往鲜为人知的电学行为。一种常见的非常规导电形式被称为可变距离跳跃(VRH)。由于许多不同的技术上重要的固体都是VRH导体，因此对这一过程有更深刻的物理理解具有重要的实际意义。最近的实验表明，VRH传导可以产生复杂和完全意想不到的行为。为了阐明这种电导的基本原理，建议直接研究不同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. ***