STRONG COMMUTATIVITY PRESERVING MAPPINGS ON SEMIPRIME RINGS

Ali, Asif,Yasen, Muhammad,Anwar, Matloob Korean Mathematical Society 2006 대한수학회보 Vol.43 No.4

Let R be a semiprime ring and f be an endomorphism on R. If f is a strong commutativity preserving (simply, scp) map on a non-zero ideal U of R, then f is commuting on U.

Strong commutativity preserving mappings on semiprime rings

Asif Ali,Muhammad Yasen,Matloob Anwar 대한수학회 2006 대한수학회보 Vol.43 No.4

LetR be a semiprime ring and f be an endomorphismon R. Iff is a strong commutativity preserving (simply, scp) mapon a non-zero ideal U ofR, thenf is commuting on U.

Superconducting quantum interference devices made of Sb-doped Bi2Se3 topological insulator nanoribbons

김남희,김홍석,Hou Yasen,Yu Dong,도용주 한국물리학회 2020 Current Applied Physics Vol.20 No.5

We report the fabrication and characterization of superconducting quantum interference devices (SQUIDs) made of Sb-doped Bi2Se3 topological insulator (TI) nanoribbon (NR) contacted with PbIn superconducting electrodes. When an external magnetic field was applied along the NR axis, the TI NR exhibited periodic magneto-conductance oscillations, the so-called Aharonov-Bohm oscillations, owing to one-dimensional subbands. Below the superconducting transition temperature of PbIn electrodes, we observed supercurrent flow through TI NR-based SQUID. The critical current periodically modulates with a magnetic field perpendicular to the SQUID loop, revealing that the periodicity corresponds to the superconducting flux quantum. Our experimental observations can be useful to explore Majorana bound states (MBS) in TI NR, promising for developing topological quantum information devices.

Multiple andreev reflections in topological insulator nanoribbons

김락희,김남희,김봉근,Hou Yasen,Yu Dong,도용주 한국물리학회 2022 Current Applied Physics Vol.34 No.-

Superconducting proximity junctions made of topological insulator (TI) nanoribbons (NRs) provide a useful platform for studying topological superconductivity. We report on the fabrication and measurement of Josephson junctions (JJs) using Sb-doped Bi2Se3 NRs in contact with Al electrodes. Aharonov–Bohm and Altshuler– Aronov–Spivak oscillations of the axial magneto-conductance of TI NR were observed, indicating the existence of metallic surface states along the circumference of the TI NR. We observed the supercurrent in the TI NR JJ and subharmonic gap structures of the differential conductance due to multiple Andreev reflections. The interface transparency of the TI NR JJs estimated based on the excess current reaches τ = 0.83, which is among the highest values reported for TI JJs. The temperature dependence of critical current is consistent with the short and ballistic junction model confirming the formation of highly transparent superconducting contacts on the TI NR. Our observations would be useful for exploring topological Josephson effects in TI NRs.

Gate-Modulated Quantum Interference Oscillations in Sb-Doped Bi2Se3 Topological Insulator Nanoribbon

Hwang Tae-Ha,Kim Hong-Seok,Hou Yasen,Yu Dong,Doh Yong-Joo 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.9

Topological insulator nanoribbons (TI NRs) provide a useful platform to explore the phase-coherent quantum electronic transport of topological surface states, which is crucial for the development of topological quantum devices. When applied with an axial magnetic field, the TI NR exhibits magnetoconductance (MC) oscillations with a flux period of h/e, i.e., Aharonov-Bohm (AB) oscillations, and h/2e, i.e., Altshuler-Aronov-Spivak (AAS) oscillations. Herein, we present an extensive study of the AB and AAS oscillations in Sb-doped Bi2Se3 TI NR as a function of the gate voltage, revealing phase-alternating topological AB oscillations. Moreover, the ensemble-averaged fast Fourier transform analysis on the Vg-dependent MC curves indicates the suppression of the quantum interference oscillation amplitudes near the Dirac point, which is attributed to the suppression of the phase coherence length within the low carrier density region. The weak antilocalization analysis on the perpendicular MC curves confirms the idea of the suppressed coherence length near the Dirac point in the TI NR.

Superconducting proximity effects in Sb-doped Bi₂Se₃ topological insulator nanoribbon

Park, Sang-Il,Kim, Hong-Seok,Hou, Yasen,Yu, Dong,Doh, Yong-Joo The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.4

Superconducting junctions of topological insulator (TI) are expected to host Majorana bound state, which is essential for developing topological quantum information devices. In this study, we fabricated Josephson junctions (JJs) made of Sb-doped Bi2Se3 TI nanoribbon and PbIn superconducting electrodes. In the normal state, the axial magnetoresistance data exhibit periodic oscillations, so-called Aharonov-Bohm oscillations, due to a metallic surface state of TI nanoribbon. At low temperature of 1.5 K, the TI JJ reveals the superconducting proximity effects, such as the critical current and multiple Andreev reflections. Under the application of microwave, integer Shapiro steps are observed with satisfying the ac Josephson relation. Our observations indicate that highly-transparent superconducting contacts are formed at the interface between TI nanoribbon and conventional superconductor, which would be useful to explore Majorana bound state in TI.

Polymorphic Variation of Inflammation-related Genes and Risk of Non-Hodgkin Lymphoma for Uygur and Han Chinese in Xinjiang

Gu, Xia,Shen, Yan,Fu, Ling,Zuo, Hong-Yun,Yasen, Halida,He, Ping,Guo, Xin-Hong,Shi, Yu-Wei,Yusufu, Muhabaiti Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.21

Polymorphisms of inflammation-related genes have been found to be associated with non-Hodgkin lymphoma (NHL) or some of its subtypes, but only a few relevant data have been reported in China. In this study, the Snapshot method was used to assess genetic variation; a total of 14 single nucleotide polymorphisms (SNPs) for 6 inflammatory factors in 157 NHL cases (64 Uygur ethnic subjects, 93 Han Chinese) and 435 controls (231 Uygur and 204 Han Chinese) were studied from the Xinjiang province of China. Haplotype distribution was estimated using PHASE 2.3 software. Statistical differences in the genotype and haplotype frequencies between case and control groups were also considered and estimated. For the Han population, the geneotype distributions for TNF-${\alpha}rs1800629$, TNF-${\alpha}rs1800630$, IL-6 rs1800795, IL-6 rs1800797, NF-KB1 rs1585215 and TLR-4 rs4986790 showed significant differences between the case and control groups (p<0.05). The TNF-${\alpha}$ gene frequencies of ACG and CCA haplotypes in the cases were higher than in the controls (OR=2.45, 95% CI: 1.55-3.89, p=0.0002, OR=2.53, 95% CI: 1.10-5.80, p=0.029, respectively), and the same findings were detected for TNF-${\beta}$ gene CA haplotype (OR=1.87, 95% CI: 1.21-2.90, p=0.0054). However, for the Uygur population, no such significant differences were detected within the gene-type distribution of the 14 SNPs. The TNF-${\alpha}$ gene frequency of the CCA haplotype between the two groups (OR=1.98, 95% CI: 1.11-3.51, p=0.021) revealed a statistically significant difference. Our results showed that polymorphic variations of inflammation-related genes could be important to the NHL etiology of the Han population, and that these may only have limited influence on the Uygur population.

Superconducting proximity effects in Sb-doped Bi2Se3 topological insulator nanoribbon

Yong-Joo Doh,Sang-Il Park,Hong-Seok Kim,Yasen Hou,Dong Yu 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.4

Superconducting junctions of topological insulator (TI) are expected to host Majorana bound state, which is essential for developing topological quantum information devices. In this study, we fabricated Josephson junctions (JJs) made of Sb-doped Bi2Se3 TI nanoribbon and PbIn superconducting electrodes. In the normal state, the axial magnetoresistance data exhibit periodic oscillations, so-called Aharonov-Bohm oscillations, due to a metallic surface state of TI nanoribbon. At low temperature of 1.5 K, the TI JJ reveals the superconducting proximity effects, such as the critical current and multiple Andreev reflections. Under the application of microwave, integer Shapiro steps are observed with satisfying the ac Josephson relation. Our observations indicate that highly-transparent superconducting contacts are formed at the interface between TI nanoribbon and conventional superconductor, which would be useful to explore Majorana bound state in TI.