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Ferromagnetism in chiral multilayer two-dimensional semimetals
Min, Hongki,Hwang, E. H.,Das Sarma, S. American Physical Society 2017 Physical Review B Vol.95 No.15
<P>We calculate the temperature-dependent long-range magnetic coupling in the presence of dilute concentrations of random magnetic impurities in chiral multilayer two-dimensional semimetals, i. e., undoped intrinsic multilayer graphene. Assuming a carrier-mediated indirect Ruderman-Kittel-Kasuya-Yosida exchange interaction among the well-separated magnetic impurities with the itinerant carriers mediating the magnetic interaction between the impurities, we investigate the magnetic properties of intrinsic multilayer graphene using an effective chiral Hamiltonian model. We find that due to the enhanced density of states in the rhombohedral stacking sequence of graphene layers, the magnetic ordering of multilayer graphene is ferromagnetic in the continuum limit. The ferromagnetic transition temperature is calculated using a finite-temperature self-consistent field approximation and found to be within the experimentally accessible range for reasonable values of the impurity-carrier coupling.</P>
Transport Gap in Dual-Gated Graphene Bilayers Using Oxides as Dielectrics
Kayoung Lee,Fallahazad, B.,Hongki Min,Tutuc, E. IEEE 2013 IEEE transactions on electron devices Vol.60 No.1
<P>Graphene bilayers in Bernal stacking exhibit a transverse electric (E) field-dependent band gap, which can be used to increase the channel resistivity and enable higher on/off ratio devices. We provide a systematic investigation of transport characteristics in dual-gated graphene bilayer devices as a function of density and E field and at temperatures from room temperature down to 0.3 K. The sample conductivity shows finite threshold voltages along the electron and hole branches, which increase as the E field increases, similar to a gapped semiconductor. We extract the transport gap as a function of E field and discuss the impact of disorder. In addition, we show that beyond the threshold, the bilayer conductivity shows a highly linear dependence on density, which is largely insensitive to the applied E field and the temperature.</P>
Eom, Gayoung,Kim, Hongki,Hwang, Ahreum,Son, Hye-Young,Choi, Yuna,Moon, Jeong,Kim, Donghyeong,Lee, Miyeon,Lim, Eun-Kyung,Jeong, Jinyoung,Huh, Yong-Min,Seo, Min-Kyo,Kang, Taejoon,Kim, Bongsoo Wiley (John WileySons) 2017 Advanced functional materials Vol.27 No.37
<P>Telomerase has attracted much attention as a universal cancer biomarker because telomerase is overexpressed in more than 85% of human cancer cells while suppressed in normal somatic cells. Since a strong association exists between telomerase activity and human cancers, the development of effective telomerase activity assay is critically important. Here, a nanogap-rich Au nanowire (NW) surface-enhanced Raman scattering (SERS) sensor is reported for detection of telomerase activity in various cancer cells and tissues. The nanogap-rich Au NWs are constructed by deposition of nano-particles on single-crystalline Au NWs and provided highly reproducible SERS spectra. The telomeric substrate (TS) primer-attached nanogap-rich Au NWs can detect telomerase activity through SERS measurement after the elongation of TS primers, folding into G-quadruplex structures, and intercalation of methylene blue. This sensor enables us to detect telomerase activity from various cancer cell lines with a detection limit of 0.2 cancer cells mL(-1). Importantly, the nanogap-rich Au NW sensor can diagnose gastric and breast cancer tissues accurately. The nanogap-rich Au NW sensors show strong SERS signals only in the presence of tumor tissues excised from 16 tumor-bearing mice, while negligible signals in the presence of heated tumor tissues or normal tissues. It is anticipated that nanogap-rich Au NW SERS sensors can be used for a universal cancer diagnosis and further biomedical applications including a diverse biomarker sensing.</P>