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Searching for Flat Bands in Moire Gr...

Scheer, Michael G.,

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Searching for Flat Bands in Moire Graphene /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Searching for Flat Bands in Moire Graphene // Michael G Scheer.
作者:	Scheer, Michael G.,
面頁冊數:	1 electronic resource (200 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
Contained By:	Dissertations Abstracts International86-12B.
標題:	Condensed matter physics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32002744
ISBN:	9798280746985

Searching for Flat Bands in Moire Graphene /
Scheer, Michael G.,

Searching for Flat Bands in Moire Graphene /Michael G Scheer. - 1 electronic resource (200 pages)

Source: Dissertations Abstracts International, Volume: 86-12, Section: B.

Non-trivial flat bands often give rise to strongly interacting physics in solid state systems. In recent years, the flat bands in twisted bilayer graphene (TBG) near the magic angle have attracted great attention both theoretically and experimentally because of their correlated insulator and unconventional superconducting states. In this dissertation, we describe novel moire graphene constructions that yield non-trivial flat bands of a different nature to those in TBG. In particular, we focus on the flat bands arising in one-orbital kagome and two-orbital honeycomb lattice tight-binding models due to wavefunction interference.After a brief introduction, we begin Ch. 2 by analyzing TBG near commensuration. We show that twisting bilayer graphene slightly away from any commensurate angle yields a moire material. Although the magic angles in these materials are likely too small for experimental realization, we additionally discover a parameter regime in the abstract model yielding many kagome and honeycomb lattice flat bands simultaneously. Since these results cannot be realized with TBG near commensuration, the focus of Ch. 3 is on physical moire constructions approximately realizing this parameter regime. The most experimentally feasible construction in Ch. 3 consists of placing graphene on a substrate material with a lattice constant chosen to couple the two graphene valleys. We show that this model may give rise to many interesting low energy band structures including those with kagome or honeycomb lattice flat bands. Additionally, if the substrate has spin-orbit coupling, the low energy bands may have high spin Chern numbers.Finally, in Ch. 4 we consider moire systems including graphene layers with extrinsically induced Kekule-O orders. This type of order can be induced by lithium intercalation or deposition, and in a single graphene layer it couples the valleys and opens a band gap. We show that a moire system consisting of a layer of normal graphene twisted relative to a layer of Kekule-O graphene can realize honeycomb lattice flat bands. Furthermore, we show that a moire system consisting of two layers of Kekule-O graphene with a relative twist can realize kagome lattice flat bands.

English

ISBN: 9798280746985Subjects--Topical Terms:

3173567
Condensed matter physics.
Subjects--Index Terms:

Flat band

Searching for Flat Bands in Moire Graphene /
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520 $a Non-trivial flat bands often give rise to strongly interacting physics in solid state systems. In recent years, the flat bands in twisted bilayer graphene (TBG) near the magic angle have attracted great attention both theoretically and experimentally because of their correlated insulator and unconventional superconducting states. In this dissertation, we describe novel moire graphene constructions that yield non-trivial flat bands of a different nature to those in TBG. In particular, we focus on the flat bands arising in one-orbital kagome and two-orbital honeycomb lattice tight-binding models due to wavefunction interference.After a brief introduction, we begin Ch. 2 by analyzing TBG near commensuration. We show that twisting bilayer graphene slightly away from any commensurate angle yields a moire material. Although the magic angles in these materials are likely too small for experimental realization, we additionally discover a parameter regime in the abstract model yielding many kagome and honeycomb lattice flat bands simultaneously. Since these results cannot be realized with TBG near commensuration, the focus of Ch. 3 is on physical moire constructions approximately realizing this parameter regime. The most experimentally feasible construction in Ch. 3 consists of placing graphene on a substrate material with a lattice constant chosen to couple the two graphene valleys. We show that this model may give rise to many interesting low energy band structures including those with kagome or honeycomb lattice flat bands. Additionally, if the substrate has spin-orbit coupling, the low energy bands may have high spin Chern numbers.Finally, in Ch. 4 we consider moire systems including graphene layers with extrinsically induced Kekule-O orders. This type of order can be induced by lithium intercalation or deposition, and in a single graphene layer it couples the valleys and opens a band gap. We show that a moire system consisting of a layer of normal graphene twisted relative to a layer of Kekule-O graphene can realize honeycomb lattice flat bands. Furthermore, we show that a moire system consisting of two layers of Kekule-O graphene with a relative twist can realize kagome lattice flat bands.
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