Title: Many-body
states and topological properties of low-dimensional quantum materials probed
by electron transport measurements
일시 : 2022년 3월 29일(화), 17시
Speaker: 김민수(경희대학교)
Abstract : Understanding of the interaction-induced many-body states and topology of quantum matter have been at the heart of the study of modern condensed matter physics ever since its development. In low-dimensional mesoscopic systems, measurements of transport properties allow us to acquire details of the physics of condensed matter systems. Two-dimensional (2D) cleavable materials, known as van der Waals materials, have a defect-free crystalline structure that is suitable for use in high-quality quantum devices. It is even possible to obtain a single layer of these materials and build heterostructures exhibiting interesting many-body interaction-induced quantum phenomena.
In this
talk, at first, I will introduce the field from my own perspective, explain
what makes these 2D crystals so special and how they can be exploited to unveil
the new mesoscopic quantum transport phenomena. I will then discuss some of my
recent contributions to the field for the investigation on many-body states and
topologically non-trivial properties in different 2D materials. I will begin by
introducing the Hall micromagnetometry technique to quantitatively estimate extremely
small magnetic field arising from ferromagnetic 2D material CrBr3.
The observed ferromagnetic behaviour, that remains down to monolayer, is
markedly different from that given by the simple 2D Ising model normally
expected to describe 2D easy-axis ferromagnetism [1]. I will also show quantum
transport properties of 2D triangular mesh of 1D conductive wires in marginally
twisted bilayer graphene. Topologically protected 1D transport channels
exhibits giant Aharonov-Bohm oscillations that reach in amplitude up to 50 % of
resistivity and persist to temperatures above 100 K [2]. At last, I will
present electron hydrodynamics study in graphene, as a recently-discovered
approach to measure the strength of electron-electron interactions, that
provides a guidance for future attempts to achieve proximity screening of
many-body phenomena in 2D systems [3]. I am going to conclude this talk by
discussing some of the possible future researches on low dimensional quantum
materials.
References
[1] Minsoo
Kim et al., “Micromagnetometry of two-dimensional ferromagnets”, Nature Electronics 2, 457–463 (2019)
[2]
Shuigang Xu et al., “Giant oscillations in a triangular network of
one-dimensional states in marginally twisted graphene” – Nature Communications 10,
4008 (2019)
[3] Minsoo Kim et al., “Control of electron-electron interaction in graphene by proximity screenings” – Nature Communications 11, 2339 (2020).