Asian Network Mini-School on Quantum Materials 2024
Quantum materials is a general term in condensed matter physics that includes all materials whose essential properties requires advanced quantum mechanics to explain. There is a wide variety of phenomena involving quantum materials, including, but not limited to, superconductivity, topological phases of matter, quantum optics, quantum computing, spintronics, etc. Many of these phenomena arise from dimensional reduction, interactions between constituent particles, or the specific geometry of electronic structures. The phenomena and properties of these materials have been the subject of active studies worldwide to investigate their physical mechanisms and explore their potential applications in electronics and information technology.
Within Indonesia, it is realized that participating in research on quantum materials is important for the future development of our country. However, the research interest in this field has been growing in only a small theoretical physics community. Hence, promoting this research field to a broader scientific community is essential. This motivates us to propose a mini-school on quantum materials to raise awareness of the current research progress and introduce to our scientific community the relevant knowledge and tools needed to perform research in this field through lectures and hands-on training. The purpose of this Asian Network Mini-School is to allow scientists, especially early career researchers and graduate students in Indonesia and the neighboring Southeast Asian countries as members of the network, to interact with and gain advanced knowledge from experts in the related fields from ICTP, APCTP, PCS-IBS, and other institutes. This mini-school also encourages active interaction between invited lecturers, academics, researchers, and graduate students to share their work and ideas, get information regarding current research trends, and initiate possible collaborations.
This meeting is part of a series of events (https://pcs.ibs.re.kr/ICTP_Asian_Network/ICTP_Events.html) held by our ICTP Asian Network (https://pcs.ibs.re.kr/ICTP_Asian_Network/ICTP_Asian_Network.html ). In particular, our Network is planning Mini-Schools in each year of the three years 2023, 2024 and 2025. This event follows on from the successful Network Mini-School on Quantum Computing and Simulation held from 6-8 December 2023 at BRIN, Serpong Indonesia. It will be followed up by a more advanced Network Mini-Workshop on Magnetism and Spectroscopy to be held from 16-17 November 2024 at SUT, Nakhon Ratchasima, Thailand.
Venue: Auditorium Prof. Dr. Soemantri Brodjonegoro, Building B, Faculty of Mathematics and Natural Sciences (FMIPA UI)
Program Structure
The school lectures will be of pedagogical nature and offer an introductory level suited to advanced undergraduate and graduate students in physics and materials science. These students are in the stage of doing their dissertation, theses, or final projects in the fields of condensed matter physics, materials science and complex systems. Other participants include postdoctoral fellows, or those who obtained their Ph.D. degrees within five years prior to the school, as well as early career researchers. This activity is open to participants from all APCTP Member Countries and ICTP OEA regional countries on the UNESCO list, with the primary target audience being scientists and students residing in Indonesia.
The Mini-School program consists of lectures suited for advanced students and is given by invited scientists who are active practitioners in their research fields. Some lecturers will provide two (2) continuing one-hour lectures, while others will give one-hour lectures. The first few lectures will be at an introductory level. They will cover the physical concepts of topological phases of matter, spintronics, and other phenomena of quantum materials, the experimental findings that reveal them, and the current research progress in the related fields. The following lectures will address how research in this field is approached theoretically through first principles techniques and modelings. The last few lectures will be provided for hands-on training on several software packages relevant to research in this field. The second half of the last day of the mini-school will be designated for poster sessions. The poster sessions will exhibit the current research work of participants in theoretical and experimental condensed matter physics and materials science. To encourage discussion among invited lecturers and speakers, researchers, and students, there will be sufficient time allotted for open forums and coffee breaks after each lecture and during the poster session.
Time |
Monday, Sept 2nd 2024 |
Tuesday, Sept 3rd 2024 |
Wednesday, Sept 4th 2024 |
08.00 – 08.30 |
Registration |
||
08.30 – 09.00 |
Opening |
||
09.00 – 10.00 |
Lecture 1 (part 1): Han Woong Yeom |
Lecture 4 (part 1): Koichi Kusakabe |
Lecture 7 (part 1): Jung-Wan Ryu |
10.00 – 10.30 |
Coffee Break |
||
10.30 – 11.30 |
Lecture 1 (part 2): Han Woong Yeom |
Lecture 4 (part 2): Koichi Kusakabe |
Lecture 7 (part 2): Jung-Wan Ryu |
11.30 – 13.00 |
Lunch |
||
13.00 – 14.00 |
Poster Session 1 |
Poster Session 2 |
Lecture 8: Muhammad Aziz Majidi |
14.00 – 14.15 |
Coffee Break |
||
14.15 – 15.15 |
Lecture 2 (part 1): Do Van Nam |
Lecture 5 (part 1): Daniel Leykam |
Lecture 9 (part 1): Ahmad Ridwan Tresna Nugraha |
15.15 – 15.30 |
Coffee Break |
||
15.30 – 16.30 |
Lecture 2 (part 2): Do Van Nam |
Lecture 5 (part 2): Daniel Leykam |
Lecture 9 (part 2): Ahmad Ridwan Tresna Nugraha |
16.30 – 16.45 |
Coffee Break |
||
16.45 – 17.45 |
Lecture 3: Adam Badra Cahaya |
Lecture 6: Moh. Adhib Ulil Absor |
Closing |
Abstracts
^{1} Center for Artificial Low-Dimensional Electronic Systems, Institute for Basic Science
^{2} Professor at Department of Physics, POSTECH
Email: yeom@postech.ac.kr
Topological excitations or domain walls (DWs) are ubiquitous in magnetic, ferroelectric, multiferroic, and charge density wave (CDW) materials with critical roles in a variety of emerging physics and functionality. The fundamental understanding of DWs in CDW systems is based on the concept of topological solitons 1D CDW systems, which have been microscopically characterized in recent years [1, 2]. However, the atomic structure and electronic states of DWs in 2D CDW systems have not been sufficiently clear. In this talk, we will review our recent research activity for atomic scale observation and manipulation of DW topological excitations in prototypical 2D CDW systems with strong many-body interactions. Domain walls of the unique Mott-CDW insulating states of 1T-TaS_{2} are investigated in great detail [3-5], which have been related to emerging superconductivity and memristic switching behavior. We will first introduce atomic and electronic structures of a variety of DWs in this system, which include distinct electronic states within the Mott gap. The in-gap states are largely determined by strong electron correlation and structural reconstructions, indicating the multiple internal degrees of freedom within DWs [4]. A network of such DWs is also formed and hosts novel electronic states, which are related to the emergence of flat bands and superconductivity [5]. In another prototypical 2D CDW of 2H-NbSe_{2}, the CDW ground state has been known as being incommensurate, but the DWs for the incommensuration had not been identified. An unusual DW structure is introduced in this system, which is formed by the competition of two distinct CDW structures [6]. For the other prototypical CDW system of TiSe_{2}, we for the first time clarified DWs connecting chiral CDW domains. These chiral DWs do not exhibit any in-gap states, defying the general concept of a CDW DW and denying its role in emerging superconductivity [7]. All these results converge to tell us the rich physics within topological excitations through the intricate interplay of diverse interactions, which in turn indicates the possibility of manipulating exotic quantum states through topological excitations in 1D/2D systems.
- [1] S. M. Cheon, S.-H. Lee, T.-H. Kim and H. W. Yeom, Science 350 (2015), 6257.
- T J. W. Park, E. Do, J. S. Shin, S. K. Song, O. Stetsovych, P. Jelinek, and H. W. Yeom, Nature Nanotechnology 17, 244 (2022).
- D. Cho et al., Nat. Commun. 7 (2016), 10453.
- D. Cho et al., Nat. Commun. 8 (2017), 392.
- J. H. Park, G. Y. Cho, D. Cho, and H. W. Yeom, Nat. Commun. 10, 4038 (2019).
- G. Gye, E. Oh, and H. W. Yeom, Phys. Rev. Lett. 122, 016403 (2019).
- H. J. Kim, K.-H. Jin, and H. W. Yeom, submitted (2024).
^{1} Associate Professor at Phenikaa University, Hanoi, Vietnam
Assistant Professor, Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, 16424, INDONESIA
Email: adam@sci.ui.ac.id
In recent years, spintronics, or spin electronics, has emerged as a pivotal field in condensed matter physics, offering transformative potential for future electronic devices through the manipulation of electron spin rather than charge. This talk presents a lecture on the cutting-edge phenomena of spin pumping and spin-orbit torque (SOT), which are pivotal to the evolving field of spintronics. This lecture will provide a comprehensive overview of the theoretical foundations and experimental breakthroughs that have propelled these phenomena to the forefront of condensed matter physics research. Spin pumping serves as a fundamental mechanism for generating pure spin currents. Spin pumping involves the transfer of angular momentum from a precessing magnetization in a ferromagnetic material to an adjacent non-magnetic layer in form of a pure spin current. This mechanism is instrumental in a variety of spintronic applications, including enhanced magnetic damping and spin current generation, which are essential for the development of next-generation electronic devices [1].
Spin-orbit torque, on the other hand, emerges from the coupling between the spin and orbital degrees of freedom in materials with strong spin-orbit interaction. This effect enables the manipulation of magnetic states through electrical currents, offering a highly efficient pathway for magnetic switching. The ability to control magnetization dynamically and with low power consumption makes spin-orbit torque a cornerstone for advancements in non-volatile memory technologies and other spintronic applications [2]. This talk discusses the theoretical models that describe spin pumping and spin-orbit torque, as well as recent research developments and the practical implications of these phenomena in the context of modern spintronic devices.
- A.B. Cahaya, A. O., Leon, & G.E.W. Bauer (2017). Crystal field effects on spin pumping. Physical Review B, 96(14), 144434..
- A.B. Cahaya, A. O. Leon, & M.H. Fauzi (2023). Spin–orbit torque on nuclear spins exerted by a spin accumulation via hyperfine interactions. Nanotechnology, 34(50), 505001.
Professor, University of Hyogo, Japan
Email: kusakabe@sci.u-hyogo.ac.jp
Materials with potential applications for spintronics and quantum information processing include stacked atomic layers. In particular, typical materials such as graphene and hexagonal BN have an advantage that, in their crystalline form, the materials themselves have no local magnetic moment. We have shown that, in graphene and BN, even strong magnetism can be realized by modifying the atomic-scale material structure. We will present several examples of our research, including ongoing collaborations between Japan and Indonesia. [1-6] In particular, these systems exhibit the designed metal-insulator transition, artificially realized magnetic ordering, strongly correlated quantum effects, entangled spin states, etc. in the designed heterostructures. As a result, our research suggests that we can theoretically propose structures that can surpass the spin conduction and quantum information processing that have already been realized. In the first part of this lecture, examples of heterostructures that can be applied to spintronics and quantum information processing are presented. The second part outlines electronic structure calculation methods used in our theoretical design.
- Harfah, Y. Wicaksono, G. K. Sunnardianto, M. A. Majidi, and K. Kusakabe, “Ultra-thin van der Waals magnetic tunnel junction based on monoatomic boron vacancy of hexagonal boron nitride”, Phys. Chem. Chem. Phys., 26, 9733 (2024).
- Wicaksono, H. Harfah, G. K. Sunnardianto, M. A. Majidi, and K. Kusakabe, “Colossal In-plane Magnetoresistance Ratio of Graphene Sandwiched with Ni Nanostructures”, RSC Adv., 12, 13985 (2022).
- Morishita, Y. Oishi, T. Yamaguchi, K. Kusakabe, “S=1 antiferromagnetic electron-spin systems on hydrogenated phenalenyl-tessellation molecules for material-based quantum-computation resources”, Appl. Phys. Express, 14, 121005 (2021).
- Harfah, Y. Wicaksono, M.A. Majidi, and K. Kusakabe, “Spin-current control by induced electric-polarization reversal in Ni/hBN/Ni: A cross-correlation material”, ACS Appl. Elec. Materials, 2, 1689 (2020).
- Wicaksono, S. Teranishi, K. Nishiguchi, K. Kusakabe, “Tunable induced magnetic moment and in-planeconductance of graphene in Ni/Graphene/Ni nano spin-valve like structure: a first principles study”, CARBON, 143, 828 (2019).
- Kusakabe and M. Maruyama, “Magnetic nanographite”, Phys. Rev. B, 67 (2003) 092406.
Researcher at Science, Mathematics and Technology Cluster, Singapore University of Technology and Design
Email: daniel.leykam@gmail.com
There is a great deal of ongoing interest in topological materials including graphene, topological insulators, and Weyl semimetals. These are condensed matter systems with novel electronic properties such as disorder-robust conducting edge states that are protected by the abstract mathematics of topology. Photonics provides a highly flexible platform for emulating and better understanding these exotic materials. First, I will survey methods for emulating the single particle Hamiltonians describing various quantum materials using light propagation in coupled cavities and waveguide arrays. Next, I will discuss exciting recent progress towards the photonic emulation of strongly-correlated quantum materials. Finally, I will show how suitably-tailored optical nonlinearities or losses can be used to achieve a controlled “filling” of photonic bands, mimicking electronic topological insulators.
Associate Professor, Department of Physics, Faculty of Mathematics and Natural Sciences,
Gadjah Mada University, Yogyakarta, INDONESIA
Email: adib@ugm.ac.id
Spin-orbit coupling (SOC), which links the spin degree of freedom with the orbital motion of electrons in crystalline solids, is crucial for the development of new physical phenomena. In non-centrosymmetric materials, SOC aligns the electron’s spin direction with its momentum, resulting in complex spin textures in reciprocal k-space. Depending on the crystal symmetry, these spin textures can manifest as Rashba, Dresselhaus, persistent, or more complex configurations. In this talk, we will present our recent findings on spin-textured physics in 2D-related materials [1-8] and discuss their potential implications for spintronic applications. Specifically, we have delved into the emergence of persistent spin textures, a characteristic of certain materials that allows them to maintain a consistent spin configuration in momentum space. This feature is predicted to result in an exceptionally long spin lifetime for carriers, which is promising for dissipationless spintronics devices.
Keywords: Spintronics, spin textures, spin-orbit coupling.
- Absor, M.A.U, Santoso I, and Harsojo, Phys. Rev. B 109, 115141 (2024).
- Umar, M.D., Falihin, L.D. , Lukmantoro, A. , Harsojo, Absor, M.A.U., Phys. Rev. B 108, 035109 (2023).
- Lukmantoro A., Absor, M.A.U., Phys. Rev. Materials 7, 104005 (2023).
- Absor, M.A.U. , Lukmantoro A. , Santoso I., J. Phys. Cond. Matter 34, 445501 (2022).
- Absor, M.A.U., I Santoso, J. Appl. Phys. 132, 183906 (2022).
- Sasmito, S.A., Anshory, M., Jihad, I., Absor, M.A.U., Phys. Rev. B 104, 115145 (2021).
- Absor, M.A.U., and F. Ishii, Phys. Rev. B 103, 045119 (2021).
- Absor, M.A.U., and F. Ishii, Phys. Rev. B 100, 115104 (2019).
Researcher at Center of Theoretical Physics of Complex Systems – Institute of Basic Science, Daejeon, Korea
Email: jungwanryu@ibs.re.kr, jungwanryu@gmail.com
Non-hermiticity, which describes open systems with energy gain and loss, is ubiquitous in many branches of physics, such as quantum mechanics, optics, condensed matter physics, and nonlinear dynamics. In non-Hermitian systems, eigenvalues can be complex, and eigenstates can be non-orthogonal, leading to rich and novel physical phenomena not present in Hermitian systems. The topology in non-Hermitian systems arises from these intrinsic properties, in addition to the traditional Hermitian topology derived from Berry phases of eigenstates. This lecture will discuss complex eigenvalues and non-orthogonal eigenstates, the point gap of complex energy bands, exceptional points, and their topological properties in non-Hermitian systems. We will explore these phenomena in detail, examining how non-Hermitian systems extend our understanding of the topological structure of energy bands and open up new avenues for research and applications. The theoretical framework and experimental realizations of these unique topological features in various physical systems will also be discussed.
Associate Professor,
Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, 16424, INDONESIA
Email: aziz.majidi@sci.ui.ac.id
The tight-binding model, or method, has become a standard tool for constructing a Hamiltonian for a condensed-matter system using atomic orbitals or Wannier functions as its basis set. Its superiority lies in its simple structure, providing flexibility for use as a toy model to reveal a particular physical phenomenon on a qualitative level or to construct a realistic model in which the detailed crystal structure of the system and some form of interaction, such as spin-orbit coupling, need to be incorporated appropriately. Meanwhile, the Green function technique derived from Quantum Field Theory (QFT) is another powerful tool for calculating various physical quantities in condensed-matter systems based on the constructed Hamiltonian. In this lecture, I will review the concept of the tight-binding model and the procedure to build it from the Density Functional Theory (DFT) calculation results. Further, I will go through an example of capturing the surface states of a topological insulator using the Green function technique based on the constructed tight-binding Hamiltonian.
Researcher at Research Center for Quantum Physics – National Research and Innovation Agency, INDONESIA
Email: ahma080@brin.go.id
Quantum ESPRESSO is a suite of open-source codes for materials modeling and simulation, while Wannier90 is an additional tool designed for obtaining maximally-localized Wannier functions, which are crucial for some applications such as electronic structure analysis and transport properties. This tutorial talk is not intended to teach the participants for understanding all features or aspects of Quantum ESPRESSO and Wannier90, yet we hope that we can offer an accessible introduction to those two valuable computational tools in quantum and condensed matter physics. The tutorial will cover the basic principles, installation steps, key features, and practical examples of both Quantum ESPRESSO and Wannier90, providing participants with the foundational knowledge needed to start using these tools in their research.
Lecture 1
HAN WOONG YEOM^{1,2}
^{1} Center for Artificial Low-Dimensional Electronic Systems, Institute for Basic Science
^{2} Professor at Department of Physics, POSTECH
Email: yeom@postech.ac.kr
Topological excitations in van der Waals materials
Topological excitations or domain walls (DWs) are ubiquitous in magnetic, ferroelectric, multiferroic, and charge density wave (CDW) materials with critical roles in a variety of emerging physics and functionality. The fundamental understanding of DWs in CDW systems is based on the concept of topological solitons 1D CDW systems, which have been microscopically characterized in recent years [1, 2]. However, the atomic structure and electronic states of DWs in 2D CDW systems have not been sufficiently clear. In this talk, we will review our recent research activity for atomic scale observation and manipulation of DW topological excitations in prototypical 2D CDW systems with strong many-body interactions. Domain walls of the unique Mott-CDW insulating states of 1T-TaS_{2} are investigated in great detail [3-5], which have been related to emerging superconductivity and memristic switching behavior. We will first introduce atomic and electronic structures of a variety of DWs in this system, which include distinct electronic states within the Mott gap. The in-gap states are largely determined by strong electron correlation and structural reconstructions, indicating the multiple internal degrees of freedom within DWs [4]. A network of such DWs is also formed and hosts novel electronic states, which are related to the emergence of flat bands and superconductivity [5]. In another prototypical 2D CDW of 2H-NbSe_{2}, the CDW ground state has been known as being incommensurate, but the DWs for the incommensuration had not been identified. An unusual DW structure is introduced in this system, which is formed by the competition of two distinct CDW structures [6]. For the other prototypical CDW system of TiSe_{2}, we for the first time clarified DWs connecting chiral CDW domains. These chiral DWs do not exhibit any in-gap states, defying the general concept of a CDW DW and denying its role in emerging superconductivity [7]. All these results converge to tell us the rich physics within topological excitations through the intricate interplay of diverse interactions, which in turn indicates the possibility of manipulating exotic quantum states through topological excitations in 1D/2D systems.
- [1] S. M. Cheon, S.-H. Lee, T.-H. Kim and H. W. Yeom, Science 350 (2015), 6257.
- T J. W. Park, E. Do, J. S. Shin, S. K. Song, O. Stetsovych, P. Jelinek, and H. W. Yeom, Nature Nanotechnology 17, 244 (2022).
- D. Cho et al., Nat. Commun. 7 (2016), 10453.
- D. Cho et al., Nat. Commun. 8 (2017), 392.
- J. H. Park, G. Y. Cho, D. Cho, and H. W. Yeom, Nat. Commun. 10, 4038 (2019).
- G. Gye, E. Oh, and H. W. Yeom, Phys. Rev. Lett. 122, 016403 (2019).
- H. J. Kim, K.-H. Jin, and H. W. Yeom, submitted (2024).
Lecture 2
DO VAN NAM
^{1} Associate Professor at Phenikaa University, Hanoi, Vietnam
Topological Electronics of 2D Materials
Lecture 3
ADAM BADRA CAHAYA
Assistant Professor, Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, 16424, INDONESIA
Email: adam@sci.ui.ac.id
Spin Pumping and Spin-Orbit Torque
In recent years, spintronics, or spin electronics, has emerged as a pivotal field in condensed matter physics, offering transformative potential for future electronic devices through the manipulation of electron spin rather than charge. This talk presents a lecture on the cutting-edge phenomena of spin pumping and spin-orbit torque (SOT), which are pivotal to the evolving field of spintronics. This lecture will provide a comprehensive overview of the theoretical foundations and experimental breakthroughs that have propelled these phenomena to the forefront of condensed matter physics research. Spin pumping serves as a fundamental mechanism for generating pure spin currents. Spin pumping involves the transfer of angular momentum from a precessing magnetization in a ferromagnetic material to an adjacent non-magnetic layer in form of a pure spin current. This mechanism is instrumental in a variety of spintronic applications, including enhanced magnetic damping and spin current generation, which are essential for the development of next-generation electronic devices [1].
Spin-orbit torque, on the other hand, emerges from the coupling between the spin and orbital degrees of freedom in materials with strong spin-orbit interaction. This effect enables the manipulation of magnetic states through electrical currents, offering a highly efficient pathway for magnetic switching. The ability to control magnetization dynamically and with low power consumption makes spin-orbit torque a cornerstone for advancements in non-volatile memory technologies and other spintronic applications [2]. This talk discusses the theoretical models that describe spin pumping and spin-orbit torque, as well as recent research developments and the practical implications of these phenomena in the context of modern spintronic devices.
- A.B. Cahaya, A. O., Leon, & G.E.W. Bauer (2017). Crystal field effects on spin pumping. Physical Review B, 96(14), 144434..
- A.B. Cahaya, A. O. Leon, & M.H. Fauzi (2023). Spin–orbit torque on nuclear spins exerted by a spin accumulation via hyperfine interactions. Nanotechnology, 34(50), 505001.
Charge and Spin Transport in Heterostructure Systems
Materials with potential applications for spintronics and quantum information processing include stacked atomic layers. In particular, typical materials such as graphene and hexagonal BN have an advantage that, in their crystalline form, the materials themselves have no local magnetic moment. We have shown that, in graphene and BN, even strong magnetism can be realized by modifying the atomic-scale material structure. We will present several examples of our research, including ongoing collaborations between Japan and Indonesia. [1-6] In particular, these systems exhibit the designed metal-insulator transition, artificially realized magnetic ordering, strongly correlated quantum effects, entangled spin states, etc. in the designed heterostructures. As a result, our research suggests that we can theoretically propose structures that can surpass the spin conduction and quantum information processing that have already been realized. In the first part of this lecture, examples of heterostructures that can be applied to spintronics and quantum information processing are presented. The second part outlines electronic structure calculation methods used in our theoretical design.
- Harfah, Y. Wicaksono, G. K. Sunnardianto, M. A. Majidi, and K. Kusakabe, “Ultra-thin van der Waals magnetic tunnel junction based on monoatomic boron vacancy of hexagonal boron nitride”, Phys. Chem. Chem. Phys., 26, 9733 (2024).
- Wicaksono, H. Harfah, G. K. Sunnardianto, M. A. Majidi, and K. Kusakabe, “Colossal In-plane Magnetoresistance Ratio of Graphene Sandwiched with Ni Nanostructures”, RSC Adv., 12, 13985 (2022).
- Morishita, Y. Oishi, T. Yamaguchi, K. Kusakabe, “S=1 antiferromagnetic electron-spin systems on hydrogenated phenalenyl-tessellation molecules for material-based quantum-computation resources”, Appl. Phys. Express, 14, 121005 (2021).
- Harfah, Y. Wicaksono, M.A. Majidi, and K. Kusakabe, “Spin-current control by induced electric-polarization reversal in Ni/hBN/Ni: A cross-correlation material”, ACS Appl. Elec. Materials, 2, 1689 (2020).
- Wicaksono, S. Teranishi, K. Nishiguchi, K. Kusakabe, “Tunable induced magnetic moment and in-planeconductance of graphene in Ni/Graphene/Ni nano spin-valve like structure: a first principles study”, CARBON, 143, 828 (2019).
- Kusakabe and M. Maruyama, “Magnetic nanographite”, Phys. Rev. B, 67 (2003) 092406.
Lecture 5
DANIEL LEYKAM
Researcher at Science, Mathematics and Technology Cluster, Singapore University of Technology and Design
Email: daniel.leykam@gmail.com
Exploring topological properties of materials through photonics
There is a great deal of ongoing interest in topological materials including graphene, topological insulators, and Weyl semimetals. These are condensed matter systems with novel electronic properties such as disorder-robust conducting edge states that are protected by the abstract mathematics of topology. Photonics provides a highly flexible platform for emulating and better understanding these exotic materials. First, I will survey methods for emulating the single particle Hamiltonians describing various quantum materials using light propagation in coupled cavities and waveguide arrays. Next, I will discuss exciting recent progress towards the photonic emulation of strongly-correlated quantum materials. Finally, I will show how suitably-tailored optical nonlinearities or losses can be used to achieve a controlled “filling” of photonic bands, mimicking electronic topological insulators.
Lecture 6
MOH. ADHIB ULIL ABSOR
Associate Professor, Department of Physics, Faculty of Mathematics and Natural Sciences,
Gadjah Mada University, Yogyakarta, INDONESIA
Email: adib@ugm.ac.id
Development of persistent spin-textured materials for dissipationless spintronics
Spin-orbit coupling (SOC), which links the spin degree of freedom with the orbital motion of electrons in crystalline solids, is crucial for the development of new physical phenomena. In non-centrosymmetric materials, SOC aligns the electron’s spin direction with its momentum, resulting in complex spin textures in reciprocal k-space. Depending on the crystal symmetry, these spin textures can manifest as Rashba, Dresselhaus, persistent, or more complex configurations. In this talk, we will present our recent findings on spin-textured physics in 2D-related materials [1-8] and discuss their potential implications for spintronic applications. Specifically, we have delved into the emergence of persistent spin textures, a characteristic of certain materials that allows them to maintain a consistent spin configuration in momentum space. This feature is predicted to result in an exceptionally long spin lifetime for carriers, which is promising for dissipationless spintronics devices.
Keywords: Spintronics, spin textures, spin-orbit coupling.
- Absor, M.A.U, Santoso I, and Harsojo, Phys. Rev. B 109, 115141 (2024).
- Umar, M.D., Falihin, L.D. , Lukmantoro, A. , Harsojo, Absor, M.A.U., Phys. Rev. B 108, 035109 (2023).
- Lukmantoro A., Absor, M.A.U., Phys. Rev. Materials 7, 104005 (2023).
- Absor, M.A.U. , Lukmantoro A. , Santoso I., J. Phys. Cond. Matter 34, 445501 (2022).
- Absor, M.A.U., I Santoso, J. Appl. Phys. 132, 183906 (2022).
- Sasmito, S.A., Anshory, M., Jihad, I., Absor, M.A.U., Phys. Rev. B 104, 115145 (2021).
- Absor, M.A.U., and F. Ishii, Phys. Rev. B 103, 045119 (2021).
- Absor, M.A.U., and F. Ishii, Phys. Rev. B 100, 115104 (2019).
Lecture 7
JUNG-WAN RYU
Researcher at Center of Theoretical Physics of Complex Systems – Institute of Basic Science, Daejeon, Korea
Topological Structures of Energy Bands in Non-Hermitian Systems
Non-hermiticity, which describes open systems with energy gain and loss, is ubiquitous in many branches of physics, such as quantum mechanics, optics, condensed matter physics, and nonlinear dynamics. In non-Hermitian systems, eigenvalues can be complex, and eigenstates can be non-orthogonal, leading to rich and novel physical phenomena not present in Hermitian systems. The topology in non-Hermitian systems arises from these intrinsic properties, in addition to the traditional Hermitian topology derived from Berry phases of eigenstates. This lecture will discuss complex eigenvalues and non-orthogonal eigenstates, the point gap of complex energy bands, exceptional points, and their topological properties in non-Hermitian systems. We will explore these phenomena in detail, examining how non-Hermitian systems extend our understanding of the topological structure of energy bands and open up new avenues for research and applications. The theoretical framework and experimental realizations of these unique topological features in various physical systems will also be discussed.
Lecture 8
MUHAMMAD AZIZ MAJIDI
Associate Professor,
Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, 16424, INDONESIA
Email: aziz.majidi@sci.ui.ac.id
Tutorial on Tight-Binding Model and Green Function
The tight-binding model, or method, has become a standard tool for constructing a Hamiltonian for a condensed-matter system using atomic orbitals or Wannier functions as its basis set. Its superiority lies in its simple structure, providing flexibility for use as a toy model to reveal a particular physical phenomenon on a qualitative level or to construct a realistic model in which the detailed crystal structure of the system and some form of interaction, such as spin-orbit coupling, need to be incorporated appropriately. Meanwhile, the Green function technique derived from Quantum Field Theory (QFT) is another powerful tool for calculating various physical quantities in condensed-matter systems based on the constructed Hamiltonian. In this lecture, I will review the concept of the tight-binding model and the procedure to build it from the Density Functional Theory (DFT) calculation results. Further, I will go through an example of capturing the surface states of a topological insulator using the Green function technique based on the constructed tight-binding Hamiltonian.
Lecture 9
AHMAD RIDWAN TRESNA NUGRAHA
Researcher at Research Center for Quantum Physics – National Research and Innovation Agency, INDONESIA
Email: ahma080@brin.go.id
Quantum ESPRESSO and Wannier90 Crash Course
Quantum ESPRESSO is a suite of open-source codes for materials modeling and simulation, while Wannier90 is an additional tool designed for obtaining maximally-localized Wannier functions, which are crucial for some applications such as electronic structure analysis and transport properties. This tutorial talk is not intended to teach the participants for understanding all features or aspects of Quantum ESPRESSO and Wannier90, yet we hope that we can offer an accessible introduction to those two valuable computational tools in quantum and condensed matter physics. The tutorial will cover the basic principles, installation steps, key features, and practical examples of both Quantum ESPRESSO and Wannier90, providing participants with the foundational knowledge needed to start using these tools in their research.