東華大學圖書館 |

Imaging the Electronic States of Magnetic Topological Materials EuM2X2 /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Imaging the Electronic States of Magnetic Topological Materials EuM2X2 // Mingda Gong.
作者:	Gong, Mingda,
面頁冊數:	1 electronic resource (122 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
Contained By:	Dissertations Abstracts International86-12B.
標題:	Physics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32042011
ISBN:	9798315791232

Imaging the Electronic States of Magnetic Topological Materials EuM2X2 /
Gong, Mingda,

Imaging the Electronic States of Magnetic Topological Materials EuM2X2 /Mingda Gong. - 1 electronic resource (122 pages)

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

Topological materials have attracted extensive attentions from researchers in the recent decades because of their promising potentials in the development of quantum technology, disspationless transport devices, and information storage systems. Since the discovery of the integer quantum Hall effect (IQHE) in 1980, researchers discovered the robust helical edge channel protected by topological invariant due to the bulk-boundary correspondence. Starting from this foundation, theoretical and experimental researchers have proposed and realized multiple topological materials categorized as 2D and 3D topological insulators (TI) exhibiting exotic electronic properties. On top of that, by integrating magnetism into the topology, researchers explored the subsequent magnetic topological insulators with the quantum anomalous Hall effect (QAHE), as well as the most desired intrinsic magnetic topological insulators (IMTI). In addition, in some antiferromagnetic (AFM) systems with IMTI properties, either the inversion or the combinational S symmetry (S = Tτ1/2 or S = T Cn) is preserved, leading to a nontrivial ℤ2 topological insulator defined by the axion coupling term. Such IMTI is known as axion insulators, hosting half-quantized surface QAHE and offering great potential in searching of spontaneous low energy consumption electronic devices.As of now a promising material candidate for realizing IMTI and axion insulator is the EuM2X2-family (M = metal; X = group 14 or 15 elements) Zintl compounds, which has caught significant attention since 2018. The family members EuIn2As2 and EuSn2As2 are predicted to be stoichiometric magnetic topological insulators, while EuZn2As2, EuCd2As2, and EuCd2Sb2 were previously expected to host magnetic Weyl semimetallic states but received controversies in the recent two years. An issue in the synthesis of these Eu-based Zintl crystals has been their intrinsic hole-doping among all samples. A likely origin is Eu vacancies. This unavoidable hole-doping pushes the topological surface states, which are predicted to form near the Fermi energy, to higher energies above the chemical potential, away from the reach of ARPES experiments.In my Ph.D. research, I use atomically resolved scanning tunneling microscopy and spectroscopy (STM/S), complemented by DFT calculations performed by collaborated theoretical researchers, to visualize and probe the electronic states and the magnetic topological properties of EuM2X2-family materials, which leads to a deeper understanding of the interplay between magnetism and topology.This thesis discusses our projects of probing three samples in the EuM2X2-family: EuIn2As2, EuZn2As2, and EuCd2Sb2, which, from literature, are all promising magnetic topological materials. On the surface of EuIn2As2, we observe a ∼ 40 meV gap residing inside the bulk spin-orbit gap in its AFM phase, rapidly closing as temperature raises and partially merging in its PM phase at T > TN. This indicates that the topological surface states are impacted by the intrinsic magnetism, suggesting the observed gap to be related to the axion electrodynamics proposed in this material, but not yet experimentally verified.On the other hand, for EuZn2As2 and EuCd2Sb2, we present solid experimental evidence of their topologically trivial magnetic semiconducting nature, which challenges the previously expected magnetic Weyl semimetal states. The observed tip-induced band bending (TIBB) around local defects of EuZn2As2 also indicates the possibility of trapped charges and magnetic polarons induced by Eu vacancies, driving the potentially new directions of future research in these materials.

English

ISBN: 9798315791232Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Integer quantum Hall effect

Imaging the Electronic States of Magnetic Topological Materials EuM2X2 /
LDR:05193nmm a22004453i 4500 001 2438327
005 20251210114008.5
006 m o d
007 cr|nu||||||||
008 261011s2025 miu||||||m |||||||eng d
020 $a 9798315791232
035 $a (MiAaPQD)AAI32042011
035 $a AAI32042011
040 $a MiAaPQD $b eng $c MiAaPQD $e rda
100 1 $a Gong, Mingda, $e author. $0 (orcid)0000-0003-3270-1699 $3 3829594
245 1 0 $a Imaging the Electronic States of Magnetic Topological Materials EuM2X2 / $c Mingda Gong.
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2025
300 $a 1 electronic resource (122 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
500 $a Advisors: Aynajian, Pegor Committee members: Lee, Wei-Cheng; Shim, Bonggu; Zhou, Guangwen.
502 $b Ph.D. $c State University of New York at Binghamton $d 2025.
520 $a Topological materials have attracted extensive attentions from researchers in the recent decades because of their promising potentials in the development of quantum technology, disspationless transport devices, and information storage systems. Since the discovery of the integer quantum Hall effect (IQHE) in 1980, researchers discovered the robust helical edge channel protected by topological invariant due to the bulk-boundary correspondence. Starting from this foundation, theoretical and experimental researchers have proposed and realized multiple topological materials categorized as 2D and 3D topological insulators (TI) exhibiting exotic electronic properties. On top of that, by integrating magnetism into the topology, researchers explored the subsequent magnetic topological insulators with the quantum anomalous Hall effect (QAHE), as well as the most desired intrinsic magnetic topological insulators (IMTI). In addition, in some antiferromagnetic (AFM) systems with IMTI properties, either the inversion or the combinational S symmetry (S = Tτ1/2 or S = T Cn) is preserved, leading to a nontrivial ℤ2 topological insulator defined by the axion coupling term. Such IMTI is known as axion insulators, hosting half-quantized surface QAHE and offering great potential in searching of spontaneous low energy consumption electronic devices.As of now a promising material candidate for realizing IMTI and axion insulator is the EuM2X2-family (M = metal; X = group 14 or 15 elements) Zintl compounds, which has caught significant attention since 2018. The family members EuIn2As2 and EuSn2As2 are predicted to be stoichiometric magnetic topological insulators, while EuZn2As2, EuCd2As2, and EuCd2Sb2 were previously expected to host magnetic Weyl semimetallic states but received controversies in the recent two years. An issue in the synthesis of these Eu-based Zintl crystals has been their intrinsic hole-doping among all samples. A likely origin is Eu vacancies. This unavoidable hole-doping pushes the topological surface states, which are predicted to form near the Fermi energy, to higher energies above the chemical potential, away from the reach of ARPES experiments.In my Ph.D. research, I use atomically resolved scanning tunneling microscopy and spectroscopy (STM/S), complemented by DFT calculations performed by collaborated theoretical researchers, to visualize and probe the electronic states and the magnetic topological properties of EuM2X2-family materials, which leads to a deeper understanding of the interplay between magnetism and topology.This thesis discusses our projects of probing three samples in the EuM2X2-family: EuIn2As2, EuZn2As2, and EuCd2Sb2, which, from literature, are all promising magnetic topological materials. On the surface of EuIn2As2, we observe a ∼ 40 meV gap residing inside the bulk spin-orbit gap in its AFM phase, rapidly closing as temperature raises and partially merging in its PM phase at T > TN. This indicates that the topological surface states are impacted by the intrinsic magnetism, suggesting the observed gap to be related to the axion electrodynamics proposed in this material, but not yet experimentally verified.On the other hand, for EuZn2As2 and EuCd2Sb2, we present solid experimental evidence of their topologically trivial magnetic semiconducting nature, which challenges the previously expected magnetic Weyl semimetal states. The observed tip-induced band bending (TIBB) around local defects of EuZn2As2 also indicates the possibility of trapped charges and magnetic polarons induced by Eu vacancies, driving the potentially new directions of future research in these materials.
546 $a English
590 $a School code: 0792
650 4 $a Physics. $3 516296
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Materials science. $3 543314
650 4 $a Quantum physics. $3 726746
653 $a Integer quantum Hall effect
653 $a Topological insulators
653 $a Antiferromagnetics
653 $a Intrinsic magnetic topological insulators
653 $a Quantum anomalous Hall effect
690 $a 0605
690 $a 0599
690 $a 0794
690 $a 0611
710 2 $a State University of New York at Binghamton. $b Physics, Applied Physics, and Astronomy. $e degree granting institution. $3 3829595
720 1 $a Aynajian, Pegor $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-12B.
790 $a 0792
791 $a Ph.D.
792 $a 2025
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32042011