Changli Yang

Large-Area and High-Quality 2D Transition Metal Telluride

Large-area and high-quality 2D transition metal tellurides are synthesized by the chemical vapor deposition method. The as-grown WTe2 maintains two different stacking sequences in the bilayer, where the atomic structure of the stacking boundary is revealed by scanning transmission electron microscopy. The low-temperature transport measurements reveal a novel semimetal-to-insulator transition in WTe2 layers and an enhanced superconductivity in few-layer MoTe2 .

Proximity effect at superconducting Sn-Bi2Se3 interface

We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions down to 250mK and in different magnetic fields. A number of conductance anomalies were observed below the superconducting transition temperature of Sn, including a small gap that is different from that of Sn, and a zero-bias conductance peak that increases at lower temperatures. We discussed the possible origins of the smaller gap and the zero-bias conductance peak. These phenomena support the idea that a proximity-effect-induced chiral superconducting phase is formed at the interface between the superconducting Sn and the strong spin-orbit coupling material Bi2Se3.

Influence of a parallel magnetic field on the microwave photoconductivity in a high-mobility two-dimensional electron system

The electron Hamiltonian of narrow semiconductor rings with the Rashba and Dresselhaus spin orbit terms is invariant under time-reversal operation followed by a large gauge transformation. We find that all the eigenstates are doubly degenerate when integer or half-integer quantum fluxes thread the quantum ring. The wavefunctions of a degenerate pair are related to each other by the symmetry operation. These results are valid even in the presence of a disorder potential. When the Zeeman term is present only some of these degenerate levels anticross.

Microwave photoresistance of a high-mobility two-dimensional electron gas in a triangular antidot lattice

The microwave (MW) photoresistance has been measured on a high-mobility two-dimensional electron gas patterned with a shallow triangular antidot lattice, where both the MW-induced resistance oscillations (MIRO) and magnetoplasmon (MP) resonance are observed superposing on sharp commensurate geometrical resonance (GR). Analysis shows that the MIRO, MP, and GR are decoupled from each other in these experiments.

OSCILLATORY AND VANISHING RESISTANCE STATES IN MICROWAVE IRRADIATED 2D ELECTRON SYSTEMS

Giant-amplitude oscillations in dc magnetoresistance of a high-mobility two-dimensional electron system can be induced by millimeterwave irradiations, leading to zero-resistance states at the oscillation minima. Following a brief overview of the now well-known phenomenon, this paper reports on aspects of more recent experiments on the subject. These are: new zero-resistance states associated with multi-photon processes; suppression of Shubnikov-de Haas oscillations by high-frequency microwaves; and microwave photoconductivity of a high-mobility two-dimensional hole system.

Anomalous magnetic moments as evidence of chiral superconductivity in a Bi/Ni bilayer

Junhua Wang, ∗ Xinxin Gong, ∗ Guang Yang, Zhaozheng Lyu, Yuan Pang, Guangtong Liu, Zhongqing Ji, Jie Fan, Xiunian Jing, 3 Changli Yang, 3 Fanming Qu, Xiaofeng Jin, † and Li Lu 3, 4, † Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China Collaborative Innovation Center of Quantum Matter, Beijing 100871, People’s Republic of China School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, People’s Republic of China (Dated: March 21, 2018)

2kF-selected conductance oscillations of high-mobility two-dimensional electron gas in Corbino devices

We have observed electrical-field induced magneto-conductivity oscillations measured in Corbino samples made of a GaAs high-mobility two-dimensional electron gas, and found a consistent interpretation based on a semiclassical model of 2kF-selected orbital transitions between N and N + 1, 2, 3,…, Landau levels at respective local potentials, where kF is the Fermi wavevector. From the oscillation period, we deduce an effective mass value, which is consistent with the bare electron band mass of GaAs. In the same devices but with a vanishing electrical field and at elevated temperatures, we observed additional oscillation features, which can be attributed to cyclotron resonance by population of acoustic phonons. We thus demonstrate a method to determine the carrier effective mass and the sound velocity of host crystals by standard electrical transport.

Observation of an Even–Odd Asymmetric Transport in High Landau Levels

Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells. The low-temperature longitudinal resistivity (ρxx ) data demonstrate that a striking even–odd asymmetric transport exists along the [ ] direction at half filling in N ≥ 2 high Landau levels. Although the origin for the peculiar even–odd asymmetry remains unclear, we propose that the coupling strength between electrons within the same Landau level and between the neighboring two Landau levels should be considered in future studies. The tilt field data show that the in-plane field can suppress the formation of both bubble and stripe phases.