**ABOUT ME:**** **

Dr. Adam Badra Cahaya received his B.Sc in 2013 and M.Sc in 2015 from Department of Physics, Tohoku University. He received Dr. Sc. degree with dissertation entitled “Spin, charge and heat coupling at magnetic interfaces” from Interdepartmental Doctoral Degree Program for Multi-Dimensional Material Science Leaders of the same university. His doctoral study was done under JSPS Research Fellowships for Young Scientist.

**Email :** adam [at] sci.ui.ac.id

**Awards**

2008 Satyalancana Wira Karya from Presiden Indonesia

2012 Young Scientist Award from Aoba Society for the Promotion of Science 青葉理学振興会奨励賞.

**Grants**

2022 – 2023 “Pemodelan Teoretis Produksi Arus Memanfaatkan Spin Nuklir” from Univ. Indonesia

2022 – 2023 “Pemodelan Teoretis Mekanisme Produksi Arus Listrik Memanfaatkan Impuritas Logam Tanah Jarang” from Univ. Indonesia

2022 – 2023 “Pemodelan Teoretis Mekanisme Kontrol Magnetisasi Memanfaatkan Interaksi Spin-Orbit Antarmuka” from Univ. Indonesia

2020 – 2021 “Pemodelan Teoritis Struktur Pita Elektron dari Semikonduktor untuk Aplikasi Konversi Energi” from Univ. Indonesia

2020 – 2021 “Pemodelan Teoritis Resonansi Magnetik Inti pada Logam Berat” from Univ. Indonesia

2020 – 2021 “Pemodelan Teoritis Efek Spin Transfer Torque pada Logam Berat” from Univ. Indonesia

2020 – 2021 “Kajian Teoretis Efek Impuritas Permukaan pada Sifat Magnetis Logam Berat” from Univ. Indonesia

2020 – 2021 “Kajian Teoretis Transfer Energi Spin dalam Baterai Berbasis Spin Nuklir” from Univ. Indonesia

2015 – 2018 “Antiferromagnetic spin Seebeck effect” from JSPS

**Scholarships**

2015 – 2018 Japan Society for the Promotion of Science (JSPS) Fellowship for Young Scientists.

2008 – 2015 Japanese Ministry of Education and Sport (MEXT) Scholarship.

## Research interests

His research focuses on **theoretical condensed matter** and **computational material physics**. He apply theoretical and computational modeling to investigate spin-current related phenomena in nanoscale and mesoscopic magnetic heterostructures based on rare earth and heavy metals, such as indirect magnetic interactions, spin-orbit coupling, spin transfer and spin-dependent thermoelectricity.

###### Recently published

###### [1]: Twisted spin density generates anisotropic magnetic interactions.

The interactions of spins -most miniature magnets- can be isotropic or anisotropic, the latter resulting in twisted spin orientations. This article finds a simple explanation of the anisotropic interaction named Dzyaloshiskii-Moriya in metals. The model is based on two atomic spins; one of them is heavy, such as a lanthanide. As a result, a spin orientation emerges in the electrons of the metal and is perpendicular to the atomic spins. We name this as Dzyaloshisnkii-Moriya Spin-Density (DM-SD). When additional magnetic atoms are considered, the DM-SD mediates their interaction, similar to the magnetic field of large magnets’ poles, or the isotropic polarization in metals connecting far spins. The figure shows three spins (one of them, Jf, a lanthanide) and the DM-SD (colormap and small arrows) mediating their exchange.

###### [2] Orbital hybridization enhances interface phenomenon

In chemistry, the mixing of atomic orbitals form orbital hybridization. The orbital hybridization helps to explain molecule shape. In a carbon atom, for example, s and p orbitals form s-p orbital hybridization. In the band theory of solid state, orbital hybridization can also occur. For example, in the Anderson impurity model, an impurity in a sea of conduction electrons is modeled as a localized orbital and an itinerant orbital. The orbital hybridization enables the interaction between the bands. In this article, we study a spin current generation phenomenon at the interface of a magnetic material and a heavy metal. The heavy metal can be described using a generalized Anderson model with s-d orbital hybridization. By comparing the data of various heavy metals, we show that the s-d orbital hybridization enhances the spin current generation.

###### [3] Spin current generation can be enhanced by orbital moment

Due to its low intrinsic damping, rare earth iron garnet is often as spin current generator. It is actually a ferrimagnetic with antiferromagnetically coupled magnetic lattices. Here, rare earth iron garnet is described with two exchange-coupled magnetic sub-lattices. The angular momentum of rare earth reduces spin mixing conductance and magnetization. The orbital angular momentum of rare earth increases gyromagnetic ratio. Spin pumping is proportional to the difference of orbital and spin angular momentum.

**Book:**

**A.B. Cahaya**, *Fungsi khusus dan persamaan diferensial dalam fisika matematika* (UI Publishing, Jakarta, 2022).

## Student Projects

**Theoretical Condensed Matter Physics** (students of Theoretical/Computational Condensed Matter Physics Research Group, etc):

- 2020-2021:
- Faisal Kengo, Effect of Layered Dielectric Structure Variation on Light Absorption and Electric Field in Atomic Layer Material
- Muhammad Aziz Rahman, Tight-Binding Model for Graphene C-13: Investigating the Role of Electron-Phonon Coupling
- Muhammad Fadli Rais, Calculation of Light Absorption in Semiconductors with Quadratic, Quartic, and Sextic Energy Dispersions
- Rico M. Sitorus, Theoretical Modeling of Magnetic Susceptibility of Pd and Pt
- Rudye Layton, Theoretical Study of Valley Polarization in Anitimonene using Circularly-Polarized Light

- 2021-2022
- Janice A. Tombeg, Theoretical Study of Electron, Spin, and Heat Transports in Magnetic Tunnel Junction
- M. Ja’far Prakoso, Theoretical Study of Valley Polarization in Bismuthene using Circularly-Polarized Light
- Bismo Bandutomo, Magnetization Reversal Mechanism of Co/Pt and CoFeB/Pd thin films based on Fatuzzo-Labrune model
- Ansell Alvarez Anderson, RKKY Interaction in Spin Valve Structure with Semiconductor Spacer

**Computational Material Physics** (students of Exploration and Innovation of Magnetic and Dielectric Materials Research Group, etc)

- 2020-2021
- Wakid Ali Muntoha, Computational Analysis of Reflection Loss from Scattering Parameter of Electromagnetic Wave Absorbing Materials based on Nicolson-Rose-Wear method
- Rafael Ferdinandus Maniru, Law of Approach to Saturation for Determining Magnetic Intrinsic Behavior of BaFe
_{12-x}Mn_{x/2}Ti_{x/2}O_{19}and SrFe_{12-x}Mn_{x/2}Ti_{x/2}O_{19}

## Selected Publications

**A.B. Cahaya**and A.O. Leon, “Dzyaloshinskii-Moriya spin density by skew scattering”,*Phys. Rev. B***106**, L100408 (2022)**A.B. Cahaya**, R.M. Sitorus, A. Azhar, A.R.T. Nugraha, and M.A. Majidi, “Enhancement of spin-mixing conductance by*s-d*orbital hybridization in heavy metals”,*Phys. Rev. B***105***211438 (2022)***A.B. Cahaya**, “Enhancement of thermal spin pumping by orbital angular momentum of rare earth iron garnet”,*J. Magn. Magn.***553**, 169248 (2022)- M.S. Muntini, E. Suprayoga, S.A. Wella, I. Fatimah, L. Yuwana, T. Seetawan,
**A.B. Cahaya**, A.R.T. Nugraha and E.H. Hasdeo, “Spin-tunable thermoelectric performance in monolayer chromium pnictides”,*Phys. Rev. Mater.***6,**064010 (2022) **A.B. Cahaya**, A. Azhar, D. Djuhana and M.A. Majidi, “Effect of interfacial spin mixing conductance on gyromagnetic ratio of Gd substituted Y_{3}Fe_{5}O_{12}“,*Phys. Lett. A***437**, 128085 (2022)**A.B. Cahaya**, “Adiabatic limit of RKKY range function in one dimension”,*J. Magn. Magn. Mater.***547**, 168874 (2022).**A.B. Cahaya**, “Antiferromagnetic spin pumping via hyperfine interaction”,*Hyperfine Interact.***242,**46 (2021).**A.B. Cahaya**and M.A. Majidi, “Effects of screened Coulomb interaction on spin transfer torque”,*Phys. Rev. B***103**, 094420 (2021)**A.B. Cahaya**, A.O. Leon, M.R. Aliabad and G.E.W. Bauer, “Equilibrium current vortices in simple metals doped with rare earths”,*Phys. Rev. B***103**, 064433 (2021)**A.B. Cahaya**, A. Azhar and M.A. Majidi, “Yukawa potential for realistic prediction of Hubbard and Hund interaction parameters for transition metals”,*Phys. B Condens. Matter***604**, 412696 (2021)- A.O. Leon, J.D.E. Castro, J.C. Retamal,
**A.B. Cahaya**and D. Altbir, “Manipulation of the RKKY exchange by voltages”,*Phys. Rev. B***100**, 014403 (2019) - C.N. Rangkuti,
**A.B. Cahaya**, A. Azhar, M.A. Majidi and A. Rusydi, “Manifestation of charge/orbital order and charge transfer in temperature-dependent optical conductivity of single-layered Pr0.5Ca1.5MnO4”,*J. Phys. Condens. Matter***31**, 365601 (2019) - A.O. Leon,
**A.B. Cahaya**and G.E.W. Bauer, “Voltage control of rare-earth magnetic moments at the magnetic-insulatorーmetal interface”,*Phys. Rev. Lett.***120**, 027201 (2018) **A.B. Cahaya**, A.O. Leon and G.E.W. Bauer, “Crystal field effects on spin pumping”,*Phys. Rev. B***96**, 144434 (2017)**A.B. Cahaya**, O.A. Tretiakov and G.E.W. Bauer, “Spin Seebeck power conversion”,*IEEE Trans. Magn.***51**, 0800414 (2015)**A.B. Cahaya**, O.A. Tretiakov and G.E.W. Bauer, “Spin Seebeck power generators”,*Appl. Phys. Lett.***104**, 042402 (2014)