Zhengcai Xia
Huazhong University of Science and Technology
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Featured researches published by Zhengcai Xia.
Chinese Physics Letters | 2014
Wenhao Zhang; Yi Sun; Jinsong Zhang; F. Li; Minghua Guo; Yanfei Zhao; H. Zhang; J. Peng; Ying Xing; Huichao Wang; Takeshi Fujita; Akihiko Hirata; Zhi Li; Hao Ding; Chenjia Tang; Meng Wang; Qingyan Wang; Ke He; Shuai-Hua Ji; Xi Chen; Junfeng Wang; Zhengcai Xia; Liang Li; Yayu Wang; Jian Wang; Lili Wang; Mingwei Chen; Qi-Kun Xue; Xucun Ma
We prepared one-unit-cell (1-UC) thick FeSe films on insulating SrTiO3 substrates with non-superconducting FeTe protection layers by molecular beam epitaxy for ex situ studies. By direct transport and magnetic measurements, we provide definitive evidence for high temperature superconductivity in the 1-UC FeSe films with an onset TC above 40 K and an extremely large critical current density JC~1.7×106 A/cm2 at 2 K, which are much higher than TC~8 K and JC~104 A/cm2 for bulk FeSe, respectively. Our work may pave the way to enhancing and tailoring superconductivity by interface engineering.
Nature Communications | 2015
Junzhi Cao; Sihang Liang; Cheng Zhang; Yanwen Liu; J.W. Huang; Zhao Jin; Zhigang Chen; Zhijun Wang; Qisi Wang; Jun Zhao; Shiyan Li; Xi Dai; Jin Zou; Zhengcai Xia; Liang Li; Faxian Xiu
Three-dimensional topological Dirac semimetals (TDSs) are a new kind of Dirac materials that exhibit linear energy dispersion in the bulk and can be viewed as three-dimensional graphene. It has been proposed that TDSs can be driven to other exotic phases like Weyl semimetals, topological insulators and topological superconductors by breaking certain symmetries. Here we report the first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields, suggesting the removal of spin degeneracy by breaking time reversal symmetry. The detected Berry phase develops an evident angular dependence and possesses a crossover from non-trivial to trivial state under high magnetic fields, a strong hint for a fierce competition between the orbit-coupled field strength and the field-generated mass term. Our results unveil the important role of symmetry breaking in TDSs and further demonstrate a feasible path to generate a Weyl semimetal phase by breaking time reversal symmetry.
Scientific Reports | 2015
Yi Sun; Wenhao Zhang; Ying Xing; F. Li; Yanfei Zhao; Zhengcai Xia; Lili Wang; Xucun Ma; Qi-Kun Xue; Jian Wang
Interface enhanced superconductivity at two dimensional limit has become one of most intriguing research directions in condensed matter physics. Here, we report the superconducting properties of ultra-thin FeSe films with the thickness of one unit cell (1-UC) grown on conductive and insulating SrTiO3 (STO) substrates. For the 1-UC FeSe on conductive STO substrate (Nb-STO), the magnetization versus temperature (M-T) measurement shows a drop crossover around 85 K. For the FeSe films on insulating STO substrate, systematic transport measurements were carried out and the sheet resistance of FeSe films exhibits Arrhenius TAFF behavior with a crossover from a single-vortex pinning region to a collective creep region. More intriguing, sign reversal of Hall resistance with temperature is observed, demonstrating a crossover from hole conduction to electron conduction above TC in 1-UC FeSe films.
Nature Communications | 2016
Yanwen Liu; Xiang Yuan; Cheng Zhang; Zhao Jin; Awadhesh Narayan; Chen Luo; Zhigang Chen; Lei Yang; Jin Zou; Xing Wu; Stefano Sanvito; Zhengcai Xia; Liang Li; Zhong Wang; Faxian Xiu
Dirac semimetals have attracted extensive attentions in recent years. It has been theoretically suggested that many-body interactions may drive exotic phase transitions, spontaneously generating a Dirac mass for the nominally massless Dirac electrons. So far, signature of interaction-driven transition has been lacking. In this work, we report high-magnetic-field transport measurements of the Dirac semimetal candidate ZrTe5. Owing to the large g factor in ZrTe5, the Zeeman splitting can be observed at magnetic field as low as 3 T. Most prominently, high pulsed magnetic field up to 60 T drives the system into the ultra-quantum limit, where we observe abrupt changes in the magnetoresistance, indicating field-induced phase transitions. This is interpreted as an interaction-induced spontaneous mass generation of the Dirac fermions, which bears resemblance to the dynamical mass generation of nucleons in high-energy physics. Our work establishes Dirac semimetals as ideal platforms for investigating emerging correlation effects in topological matters.
Scientific Reports | 2015
Huichao Wang; Haiwen Liu; Cui-Zu Chang; Huakun Zuo; Yanfei Zhao; Yi Sun; Zhengcai Xia; Ke He; Xucun Ma; X. C. Xie; Qi-Kun Xue; Jian Wang
We report transport studies on the 5 nm thick Bi2Se3 topological insulator films which are grown via molecular beam epitaxy technique. The angle-resolved photoemission spectroscopy data show that the Fermi level of the system lies in the bulk conduction band above the Dirac point, suggesting important contribution of bulk states to the transport results. In particular, the crossover from weak antilocalization to weak localization in the bulk states is observed in the parallel magnetic field measurements up to 50 Tesla. The measured magneto-resistance exhibits interesting anisotropy with respect to the orientation of parallel magnetic field B// and the current I, signifying intrinsic spin-orbit coupling in the Bi2Se3 films. Our work directly shows the crossover of quantum interference effect in the bulk states from weak antilocalization to weak localization. It presents an important step toward a better understanding of the existing three-dimensional topological insulators and the potential applications of nano-scale topological insulator devices.
Scientific Reports | 2013
Chengliang Lu; Shuai Dong; Zhengcai Xia; Hui Luo; Zhibo Yan; Haowen Wang; Zhaoming Tian; Songliu Yuan; Tao Wu; Jun-Ming Liu
The mutual controls of ferroelectricity and magnetism are stepping towards practical applications proposed for quite a few promising devices in which multiferroic thin films are involved. Although ferroelectricity stemming from specific spiral spin ordering has been reported in highly distorted bulk perovskite manganites, the existence of magnetically induced ferroelectricity in the corresponding thin films remains an unresolved issue, which unfortunately halts this step. In this work, we report magnetically induced electric polarization and its remarkable response to magnetic field (an enhancement of ~800% upon a field of 2 Tesla at 2 K) in DyMnO3 thin films grown on Nb-SrTiO3 substrates. Accompanying with the large polarization enhancement, the ferroelectric coercivity corresponding to the magnetic chirality switching field is significantly increased. A picture based on coupled multicomponent magnetic structures is proposed to understand these features. Moreover, different magnetic anisotropy related to strain-suppressed GdFeO3-type distortion and Jahn-Teller effect is identified in the films.
Journal of Physics D | 2002
Zhengcai Xia; S.L. Yuan; F Tu; C.Q. Tang; Gang Peng; G Q Zhang; L. Liu; Junxiang Liu; Zhenhao Li; Y. Yang; C.S. Xiong; Y H Xiong
The grain-boundary structure and the temperature dependence of resistivity were investigated for (1-x)LCMO + xYSZ, where LCMO and YSZ represent La2/3Ca1/3MnO3 and yttria-stabilized zirconia, respectively. It is shown that the YSZ doped samples for x 2%. The metal-insulator transition temperature (Tp) decreases for x 2% as x is increased. LFMR increases with x for x 2%. The experimental observations are discussed on the basis of scanning electron microscopy (SEM) analysis, which reveals YSZ appearing at the grain boundaries of LCMO for x 2%.
Solid State Communications | 2002
S.L. Yuan; M.H Liu; Z.Y Li; G Peng; Zhengcai Xia; Y.P. Yang; F Tu; G Q Zhang; Juan Liu; Li Liu; J. Tang; G.H. Zhang; L.J Zhang; W. Feng; C.S Xiong; Y H Xiong
Abstract The electrical conductivity of La2/3Ca1/3MnO3 samples prepared using a sol–gel method is shown to be strongly dependent on the annealing temperature (hence the grain size). This is studied using a random resistor-network model in which ferromagnetic metallic particles with the number density p randomly fill the space of sample. The Monte Carlo simulation for the temperature dependence of resistivity shows results in excellent agreement with the experimental data measured in the larger and smaller grain size samples. From this simulation, we find that p is largely decreased for the whole temperature range below the Curie temperature as the grain size decreases. On the basis of temperature dependence of p obtained in the larger and smaller grain size samples, the effect of grain-size on the electrical transport is discussed and a possible explanation is also presented for the grain-size-dependent magnetoresistance behavior.
Scientific Reports | 2015
Chengliang Lu; Ni Hu; Ming Yang; Shuangcheng Xia; Haowen Wang; Junfeng Wang; Zhengcai Xia; Jun-Ming Liu
We report the charge-order to ferromagnetic phase transition induced by pulsed high magnetic field and impurity doping effects in manganites La0.4Ca0.6(Mn1−yCry)O3 (0 ≤ y ≤ 0.2). Significant charge-order suppression and ferromagnetic tendency upon the Cr3+-doping are evidenced, and three different ground states are identified, namely the charge-order state, the phase separated state, and the spin-glass like state. Phase diagram in the H-y plane at 4.2 K is determined by the high magnetic field study, in which the charge-order and ferromagnetic phase boundary is clearly figured out. The critical magnetic field for melting the charge-order phase of La0.4Ca0.6MnO3 is revealed to reach up to 46 T at 4.2 K. Interestingly, distinct responses of the three states to the high magnetic field are observed, indicating the special physics regarding the charge order melting process in each state. The mechanism of the doping induced charge-order suppression and ferromagnetism promotion can be understood by the competition between the antiferromagnetic interaction of Cr-Mn and local enhancement of electron hopping by Cr3+.
Frontiers of Physics in China | 2017
Xingchen Pan; Yiming Pan; Juan Jiang; Huakun Zuo; Huimei Liu; Xuliang Chen; Zhongxia Wei; Shuai Zhang; Zhihe Wang; Xiangang Wan; Zhaorong Yang; D. L. Feng; Zhengcai Xia; Liang Li; Fengqi Song; Baigeng Wang; Yuheng Zhang; Guanghou Wang
Unsaturated magnetoresistance (MR) has been reported in WTe2, and remains irrepressible up to very high field. Intense optimization of the crystalline quality causes a squarely-increasing MR, as interpreted by perfect compensation of opposite carriers. Herein we report our observation of linear MR (LMR) in WTe2 crystals, the onset of which is first identified by constructing the mobility spectra of the MR at low fields. The LMR further intensifies and predominates at fields higher than 20 Tesla while the parabolic MR gradually decays. The LMR remains unsaturated up to a high field of 60 Tesla and persists, even at a high pressure of 6.2 GPa. Assisted by density functional theory calculations and detailed mobility spectra, we find the LMR to be robust against the applications of high field, broken carrier balance, and mobility suppression. Angle-resolved photoemission spectroscopy reveals a unique quasilinear energy dispersion near the Fermi level. Our results suggest that the robust LMR is the low bound of the unsaturated MR in WTe2.