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Nanoscale Visualization of Symmetry ...

Li, Hong,

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Nanoscale Visualization of Symmetry Breaking Phenomena and Band Topology in Kagome Crystals Using Scanning Tunneling Microscopy and Spectroscopy /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Nanoscale Visualization of Symmetry Breaking Phenomena and Band Topology in Kagome Crystals Using Scanning Tunneling Microscopy and Spectroscopy // Hong Li.
Author:	Li, Hong,
Description:	1 electronic resource (138 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-12, Section: B.
Contained By:	Dissertations Abstracts International85-12B.
Subject:	Physics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31333084
ISBN:	9798383168400

Nanoscale Visualization of Symmetry Breaking Phenomena and Band Topology in Kagome Crystals Using Scanning Tunneling Microscopy and Spectroscopy /
Li, Hong,

Nanoscale Visualization of Symmetry Breaking Phenomena and Band Topology in Kagome Crystals Using Scanning Tunneling Microscopy and Spectroscopy /Hong Li. - 1 electronic resource (138 pages)

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

Kagome lattice is a versatile platform that can host both strongly correlated electronic phenomena and topological Bloch electrons. Correlated electronic states in kagome metals show some resemblance to those in high-temperature superconductors, such as cuprates and iron-based superconductors, where rotational and/or translational symmetries of the electronic structure are spontaneously broken. Many of the kagome materials are now also known to break time-reversal symmetry, even if spin magnetism is entirely absent. In our studies, we use scanning tunneling microscopy/spectroscopy (STM/S) to discover novel emergent phenomena in several representative families of kagome metals.In the first part of the thesis, I focus on a family of kagome superconductors AV3Sb5 (A = Cs, Rb, K). Using STM/S, we visualize a surprising C6 to C2 rotation symmetry breaking in the charge density wave (CDW) state of AV3Sb5. Moreover, we discover distinct temperature scales associated with a two-fold symmetric 2a0x2a0 CDW (~70+ K), a unidirectional 4a0 stripe-charge order (~50-60 K), and unidirectional coherent states in AV3Sb5 (~30-35 K). In isostructural system CsTi3Bi5 Kagome crystal, we revealed rotational symmetry breaking, or electronic nematicity, without the underlying CDW state. Our experiments shed light on a rich phase diagram hosting a variety of symmetry-breaking electronic phases in kagome metals.In the second part of the thesis, we focus on the topological aspects of the electronic band structure of kagome metals. When electrons hop (nearly) freely in kagome lattices, spin-orbit coupling can open a topological Dirac gap at the K point and induce either quantum anomalous Hall or quantum spin Hall phases when the Fermi level is positioned in the gap. In strongly spin-orbit coupled kagome metals YMn6Sn6 and TbV6Sn6, we discovered enormous crystal momentum-dependent magnetic-field induced electronic band renormalization, which could be attributed to unusual orbital magnetization. Modern orbital magnetization theory describes that orbital magnetization comes from (spin) Berry Curvature associated with the Chern Dirac band. Using quasiparticle interference imaging, we map the Dirac band renormalization under external magnetic field and measure the values of orbital magnetic moments as a function of crystal momenta. Our experiments provide the first effort to resolve momentum-space orbital magnetic moments in a single crystal with atomic resolution.

English

ISBN: 9798383168400Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Kagome lattices

Nanoscale Visualization of Symmetry Breaking Phenomena and Band Topology in Kagome Crystals Using Scanning Tunneling Microscopy and Spectroscopy /
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245 1 0 $a Nanoscale Visualization of Symmetry Breaking Phenomena and Band Topology in Kagome Crystals Using Scanning Tunneling Microscopy and Spectroscopy / $c Hong Li.
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500 $a Source: Dissertations Abstracts International, Volume: 85-12, Section: B.
500 $a Advisors: Zeljkovic, Ilija Committee members: Ran, Ying; Burch, Kenneth; Tafti, Fazel.
502 $b Ph.D. $c Boston College $d 2024.
520 $a Kagome lattice is a versatile platform that can host both strongly correlated electronic phenomena and topological Bloch electrons. Correlated electronic states in kagome metals show some resemblance to those in high-temperature superconductors, such as cuprates and iron-based superconductors, where rotational and/or translational symmetries of the electronic structure are spontaneously broken. Many of the kagome materials are now also known to break time-reversal symmetry, even if spin magnetism is entirely absent. In our studies, we use scanning tunneling microscopy/spectroscopy (STM/S) to discover novel emergent phenomena in several representative families of kagome metals.In the first part of the thesis, I focus on a family of kagome superconductors AV3Sb5 (A = Cs, Rb, K). Using STM/S, we visualize a surprising C6 to C2 rotation symmetry breaking in the charge density wave (CDW) state of AV3Sb5. Moreover, we discover distinct temperature scales associated with a two-fold symmetric 2a0x2a0 CDW (~70+ K), a unidirectional 4a0 stripe-charge order (~50-60 K), and unidirectional coherent states in AV3Sb5 (~30-35 K). In isostructural system CsTi3Bi5 Kagome crystal, we revealed rotational symmetry breaking, or electronic nematicity, without the underlying CDW state. Our experiments shed light on a rich phase diagram hosting a variety of symmetry-breaking electronic phases in kagome metals.In the second part of the thesis, we focus on the topological aspects of the electronic band structure of kagome metals. When electrons hop (nearly) freely in kagome lattices, spin-orbit coupling can open a topological Dirac gap at the K point and induce either quantum anomalous Hall or quantum spin Hall phases when the Fermi level is positioned in the gap. In strongly spin-orbit coupled kagome metals YMn6Sn6 and TbV6Sn6, we discovered enormous crystal momentum-dependent magnetic-field induced electronic band renormalization, which could be attributed to unusual orbital magnetization. Modern orbital magnetization theory describes that orbital magnetization comes from (spin) Berry Curvature associated with the Chern Dirac band. Using quasiparticle interference imaging, we map the Dirac band renormalization under external magnetic field and measure the values of orbital magnetic moments as a function of crystal momenta. Our experiments provide the first effort to resolve momentum-space orbital magnetic moments in a single crystal with atomic resolution.
546 $a English
590 $a School code: 0016
650 4 $a Physics. $3 516296
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Quantum physics. $3 726746
650 4 $a Materials science. $3 543314
653 $a Kagome lattices
653 $a Nematicity
653 $a Orbital magnetization
653 $a Smecticity
653 $a Strong correlation
653 $a Topology
690 $a 0605
690 $a 0599
690 $a 0794
690 $a 0611
710 2 $a Boston College. $b GSAS - Physics. $e degree granting institution. $3 3817168
720 1 $a Zeljkovic, Ilija $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 85-12B.
790 $a 0016
791 $a Ph.D.
792 $a 2024
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31333084