Yunyi Zang

Experimental Observation of Dirac-like Surface States and Topological Phase Transition in Pb1-xSnxTe(111) Films

The surface of a topological crystalline insulator (TCI) carries an even number of Dirac cones protected by crystalline symmetry. We epitaxially grew high-quality Pb(1-x)Sn(x)Te(111) films and investigated the TCI phase by in situ angle-resolved photoemission spectroscopy. Pb(1-x)Sn(x)Te(111) films undergo a topological phase transition from a trivial insulator to TCI via increasing the Sn/Pb ratio, accompanied by a crossover from n-type to p-type doping. In addition, a hybridization gap is opened in the surface states when the thickness of the film is reduced to the two-dimensional limit. The work demonstrates an approach to manipulating the topological properties of TCI, which is of importance for future fundamental research and applications based on TCI.

Molecular Beam Epitaxy‐Grown SnSe in the Rock‐Salt Structure: An Artificial Topological Crystalline Insulator Material

Z. Wang, J. Wang, Y. Zang, Dr. T. Jiang, Y. Gong, Prof. C.-L. Song, Prof. S.-H. Ji, Prof. L.-L. Wang, Prof. K. He, Prof. W. Duan, Prof. X. Ma, Prof. X. Chen, Prof. Q.-K. Xue State Key Laboratory of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 , China E-mail: kehe@tsinghua.edu.cn; qkxue@tsinghua.edu.cn Q. Zhang, J.-A. Shi, Prof. L. Gu Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 , China Dr. T. Jiang College of Opto-Electronic Science and Engineering National University of Defense Technology Changsha , Hunan 410073 , China Prof. S.-H. Ji, Prof. L.-L. Wang, Prof. L. Gu, Prof. K. He, Prof. W. Duan, Prof. X. Ma, Prof. X. Chen, Prof. Q.-K. Xue Collaborative Innovation Center of Quantum Matter Beijing 100084 , P. R. China

Superconductivity dichotomy in K-coated single and double unit cell FeSe films on SrTi O 3

We report the superconductivity evolution of one unit cell (1-UC) and 2-UC FeSe films on

Superconductivity in Few-layer Stanene

\mathrm{SrTi}{\mathrm{O}}_{3}

Tuning thermoelectricity in a Bi2Se3 topological insulator via varied film thickness

(001) substrates with potassium (K) adsorption. By in situ scanning tunneling spectroscopy measurement, we find that the superconductivity in 1-UC FeSe films is continuously suppressed with increasing K coverage, whereas nonsuperconducting 2-UC FeSe films become superconducting with a gap of

Dimensional Crossover Induced Topological Hall Effect in a Magnetic Topological Insulator

\ensuremath{\sim}17\phantom{\rule{0.28em}{0ex}}\mathrm{meV}

Heavily Cr-doped (Bi,Sb)2Te3 as a ferromagnetic insulator with electrically tunable conductivity

or

Thickness-dependent carrier and phonon dynamics of topological insulator Bi 2 Te 3 thin films

\ensuremath{\sim}11\phantom{\rule{0.28em}{0ex}}\mathrm{meV}

Ferromagnetism in vanadium-doped Bi2Se3 topological insulator films

depending on whether the underlying 1-UC films are superconducting or not. This work explicitly reveals that the FeSe/STO interface plays a vital role in enhancing Cooper pairing in both 1-UC and 2-UC FeSe films.

Experimental evidence of the thickness- and electric-field-dependent topological phase transitions in topological crystalline insulator SnTe(111) thin films

A single atomic slice of α-tin—stanene—has been predicted to host the quantum spin Hall effect at room temperature, offering an ideal platform to study low-dimensional and topological physics. Although recent research has focused on monolayer stanene, the quantum size effect in few-layer stanene could profoundly change material properties, but remains unexplored. By exploring the layer degree of freedom, we discover superconductivity in few-layer stanene down to a bilayer grown on PbTe, while bulk α-tin is not superconductive. Through substrate engineering, we further realize a transition from a single-band to a two-band superconductor with a doubling of the transition temperature. In situ angle-resolved photoemission spectroscopy (ARPES) together with first-principles calculations elucidate the corresponding band structure. The theory also indicates the existence of a topologically non-trivial band. Our experimental findings open up novel strategies for constructing two-dimensional topological superconductors.Stanene is a single sheet of tin atoms. Here, it is shown that a few stacked layers of stanene can be a superconductor. Changing the thickness of the substrate modifies the form of superconductivity and critical temperature.