Special topics

    SPECIAL TOPIC — Fabrication and manipulation of the second-generation quantum systems

    Default Latest Most Read
    Please wait a minute...
    For selected: Toggle thumbnails
    Up-conversion detection of mid-infrared light carrying orbital angular momentum
    Zheng Ge(葛正), Chen Yang(杨琛), Yin-Hai Li(李银海), Yan Li(李岩), Shi-Kai Liu(刘世凯), Su-Jian Niu(牛素俭), Zhi-Yuan Zhou(周志远), and Bao-Sen Shi(史保森)
    Chin. Phys. B, 2022, 31 (10): 104210.   DOI: 10.1088/1674-1056/ac6eda
    Abstract113)   HTML0)    PDF (1826KB)(32)      
    Frequency up-conversion is an effective method of mid-infrared (MIR) detection by converting long-wavelength photons to the visible domain, where efficient detectors are readily available. Here, we generate MIR light carrying orbital angular momentum (OAM) from a difference frequency generation process and perform up-conversion on it via sum frequency conversion in a bulk quasi-phase-matching crystal. The maximum quantum conversion efficiencies from MIR to visible are 34.0%, 10.4%, and 3.5% for light with topological charges of 0, 1, and 2, respectively, achieved by utilizing an optimized strong pump light. We also verify the OAM conservation with a specially designed interferometer, and the results agree well with the numerical simulations. Our study opens up the possibilities for generating, manipulating, and detecting MIR light that carries OAM, and will have great potential for optical communications and remote sensing in the MIR regime.
    Observation of multiple charge density wave phases in epitaxial monolayer 1T-VSe2 film
    Junyu Zong(宗君宇), Yang Xie(谢阳), Qinghao Meng(孟庆豪), Qichao Tian(田启超), Wang Chen(陈望), Xuedong Xie(谢学栋), Shaoen Jin(靳少恩), Yongheng Zhang(张永衡), Li Wang(王利), Wei Ren(任伟), Jian Shen(沈健), Aixi Chen(陈爱喜), Pengdong Wang(王鹏栋), Fang-Sen Li(李坊森), Zhaoyang Dong(董召阳), Can Wang(王灿), Jian-Xin Li(李建新), and Yi Zhang(张翼)
    Chin. Phys. B, 2022, 31 (10): 107301.   DOI: 10.1088/1674-1056/ac5c3e
    Abstract114)   HTML3)    PDF (2614KB)(20)      
    As a special order of electronic correlation induced by spatial modulation, the charge density wave (CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning—tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the ($sqrt{7}$ × $sqrt{3}$) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe2} film. Combining the variable-temperature angle-resolved photoemission spectroscopic (ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts Δ1 and Δ2. The gap part Δ1 that closes around ~ 150 K is accompanied with the vanish of the ($sqrt{7}$ × $sqrt{3}$) CDW phase. While another momentum-dependent gap part Δ2 can survive up to ~ 340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure Δ1 + Δ2, which suggests different forming mechanisms between the ($sqrt{7}$ × $sqrt{3}$) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe2} film as a two-dimensional (2D) material.
    Sign reversal of anisotropic magnetoresistance and anomalous thickness-dependent resistivity in Sr2CrWO6/SrTiO3 films
    Chunli Yao(姚春丽), Tingna Shao(邵婷娜), Mingrui Liu(刘明睿), Zitao Zhang(张子涛), Weimin Jiang(姜伟民), Qiang Zhao(赵强), Yujie Qiao(乔宇杰), Meihui Chen(陈美慧), Xingyu Chen(陈星宇), Ruifen Dou(窦瑞芬), Changmin Xiong(熊昌民), and Jiacai Nie(聂家财)
    Chin. Phys. B, 2022, 31 (10): 107302.   DOI: 10.1088/1674-1056/ac6164
    Abstract106)   HTML0)    PDF (1378KB)(20)      
    High-quality Sr2CrWO6 (SCWO) films have been grown on SrTiO3 (STO) substrate by pulsed laser deposition under low oxygen pressure. With decrease of the film thickness, a drastic conductivity increase is observed. The Hall measurements show that the thicker the film, the lower the carrier density. An extrinsic mechanism of charge doping due to the dominance of oxygen vacancies at SCWO/STO interfaces is proposed. The distribution and gradient of carrier concentration in SCWO films are considered to be related to this phenomenon. Resistivity behavior observed in these films is found to follow the variable range hopping model. It is revealed that with increase of the film thickness, the extent of disorder in the lattice increases, which gives a clear evidence of disorder-induced localization charge carriers in these films. Magnetoresistance measurements show that there is a negative magnetoresistance in SCWO films, which is considered to be caused by the magnetic scattering of magnetic elements Cr3+ and W5+. In addition, a sign reversal of anisotropic magnetoresistance (AMR) in SCWO film is observed for the first time, when the temperature varies across a characteristic value, TM. Magnetization—temperature measurements demonstrate that this AMR sign reversal is caused by the direction transition of easy axis of magnetization from the in-plane ferromagnetic order at T > TM to the out-of-plane at T < TM.