Heavy-quark spin polarization induced by the Kondo effect in a magnetic field

Suenaga, Daiki*; Araki, Yasufumi; Suzuki, Kei; Yasui, Shigehiro*

Physical Review D, 105(7), p.074028_1 - 074028_19, 2022/04

https://doi.org/10.1103/PhysRevD.105.074028

We propose a new mechanism of the heavy-quark spin polarization (HQSP) in quark matter induced by the Kondo effect under an external magnetic field. The Kondo effect is caused by a condensate between a heavy and a light quark called the Kondo condensate leading to a mixing of the heavy- and light-quark spins. Thus, the HQSP is driven through the Kondo effect from light quarks coupling with the magnetic field in quark matter. For demonstration, we employ the Nambu-Jona-Lasinio type model under a magnetic field and investigate the HQSP within the linear response theory with vertex corrections required by the electromagnetic gauge invariance. As a result, we find that the HQSP arises significantly with the appearance of the Kondo effect. Our findings are testable in future sign-problem-free lattice simulations.

Charge-to-spin conversion and spin diffusion in Bi/Ag bilayers observed by spin-polarized positron beam

Zhang, H. J.; Yamamoto, Shunya; Gu, B.; Li, H.; Maekawa, Masaki; Fukaya, Yuki; Kawasuso, Atsuo

Physical Review Letters, 114(16), p.166602_1 - 166602_5, 2015/04

https://doi.org/10.1103/PhysRevLett.114.166602

Charge-to-spin conversion induced by the Rashba-Edelstein effect was directly observed for the first time in samples with no magnetic layer. A spin-polarized positron beam was used to probe the spin polarization of the outermost surface electrons of Bi/Ag/AlO and Ag/Bi/AlO when charge currents were only associated with the Ag layers. An opposite surface spin polarization was found between Bi/Ag/AlO and Ag/Bi/AlO samples with the application of a charge current in the same direction. The surface spin polarizations of both systems decreased exponentially with the outermost layer thickness, suggesting the occurrence of spin diffusion from the Bi/Ag interface to the outermost surfaces. This work provides a new technique to measure spin diffusion length.

Positronium formation at low temperatures; Ideas of usage of the new Ps formation

Hirade, Tetsuya

Materials Science Forum, 445-446, p.234 - 238, 2004/02

Positronium (Ps) formation mechanism by shallowly localized long-lived electrons and positrons at low temperatures explained successfully the Ps formation enhancement at low temperatures observed in polymers and molecular solids. The expected phenomena by this Ps formation mechanism, such as effects by visible light exposure, beautiful relation between the density of shallowly localized electrons and the Ps formation and delayed Ps formation were observed. Some possibilities of application of this new Ps formation, such as a new idea of observing spin polarized positrons by this Ps formation, will be given. The shallowly localized long-lived electrons can be polarized when they are placed in magnetic field at very low temperatures. It is probably possible to see the polarity of positrons by the Ps formation with these polarized electrons. The detail of the idea will be introduced. It will be given as an invited talk.

Incommensurate magnetic ordering and spin-liquid-like state in a triangular lattice BaVS; Neutron diffraction and scattering study

Nakamura, Hiroyuki*; Yamasaki, Tomoaki*; Giri, S.*; Imai, Hideto*; Shiga, Masayuki*; Kojima, Kenji*; Nishi, Masakazu*; Kakurai, Kazuhisa*; Metoki, Naoto

Journal of the Physical Society of Japan, 69(9), p.2763 - 2766, 2000/09

https://doi.org/10.1143/JPSJ.69.2763

no abstracts in English

Optimization of dynamic nuclear polarization system for contrast variation in small angle neutron scattering

Noda, Yohei

no journal, , 

We have applied proton spin polarization to contrast variation method in small angle neutron scattering (SANS) study. Especially, we succeeded in applying this technique to silica-filled rubber, which is not easily fabricated in a deuterated form. At the last SANS experiment, degree of proton spin polarization (i.e., the population difference between up and down spins) was limited (26 % at maximum). It is essential to enhance proton spin polarization further in order to modify scattering contrast widely and separate partial scattering functions presicely. Toward this, as a result of inteisifying microwave irradiation, we finally enhanced proton spin polarization up to 50.8% for TEMPO-doped polystyrene. The achieved result will improve performance in SANS experiment at J-PARC.

Spin-polarized positron beam study of surface spin polarization

Zhang, H.; Yamamoto, Shunya; Li, H.; Maekawa, Masaki; Fukaya, Yuki; Kawasuso, Atsuo; Seki, Takeshi*; Saito, Eiji*; Takanashi, Koki*

no journal, , 

Fabrication of a new Ge-Ga source with high production efficiency by an improved metal galium target

Maekawa, Masaki; Zhou, K.*; Fukaya, Yuki; Zhang, H.; Li, H.; Kawasuso, Atsuo

no journal, , 

no abstracts in English

The First experiment of spin contrast variation SANS at J-PARC BL15 TAIKAN

Noda, Yohei; Yamaguchi, Daisuke; Shamoto, Shinichi; Hashimoto, Takeji; Kumada, Takayuki; Takata, Shinichi; Koizumi, Satoshi*; Oishi, Kazuki*; Suzuki, Junichi*; Masui, Tomomi*; et al.

no journal, , 

Neutron scattering length changes as aligning the spin direction of protons in a sample. By use of this phenomenon, we have developed spin contrast variation technique for studying nano-scale structure formed in multi-component systems. In this presentation, we report the results of our recent experiment at J-PARC TAIKAN.

Observation of vacancy-induced magnetism of zinc oxide using a spin-polarized positron beam

Abe, Hiroshi; Maekawa, Masaki; Zhou, K.*; Kawasuso, Atsuo

no journal, , 

no abstracts in English

Dynamic nuclear polarization of electron-beam irradiated and TEMPO-doped samples

Kumada, Takayuki; Noda, Yohei*; Ishikawa, Norito

no journal, , 

We compared dynamic nuclear polarization (DNP) behavior of electron-beam irradiated and TEMPO-doped samples. Both of the growth and decay rates of the nuclear polarization of the irradiated samples linearly increased with the irradiation dose, whereas those of the doped sample were quadratically proportional to the TEMPO concentration. This result suggests that the irradiated samples are polarized due to pair of free radicals produced in a spur, whereas the doped sample is polarized by unspecified TEMPO radical pairs accidentally located nearby. We suggest that higher polarization is expected by optimizing irradiation temperature, on which the radical-radical distance in the pair depends.