Quantum anomalous Hall (QAH) phase is a two-dimensional bulk ferromagnetic insulator with a nonzero Chern number in presence of spin-orbit coupling (SOC) but in the absence of applied magnetic fields. Associated metallic chiral edge states host dissipationless current transport in electronic devices. This intriguing QAH phase has recently been observed in magnetic impurity-doped topological insulators, albeit, at extremely low temperatures. Based on first-principles density functional calculations, here we predict that layered rhodium oxide K0.5RhO2 in noncoplanar chiral antiferromagnetic state is an unconventional three-dimensional QAH insulator with a large band gap and a Neel temperature of a few tens Kelvins. Furthermore, this unconventional QAH phase is revealed to be the exotic quantum topological Hall effect caused by nonzero scalar spin chirality due to the topological spin structure in the system and without the need of net magnetization and SOC.

 

fig2

 

This paper is published on Physical Review Letters 116, 256601 (2016).

Link to the full text: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.256601

June 24, 2016

We report an atomic-scale characterization of ZrTe5 by using scanning tunneling microscopy. We observe a bulk band gap of ∼80 meV with topological edge states at the step edge and, thus, demonstrate that ZrTe5 is a two-dimensional topological insulator. We also find that an applied magnetic field induces an energetic splitting of the topological edge states, which can be attributed to a strong link between the topological edge states and bulk topology. The relatively large band gap makes ZrTe5 a potential candidate for future fundamental studies and device applications.

 

ZrTe5 paper

 

This paper is published on Physical Review Letters 116, 176803 (2016).

Link to the full text: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.176803

May 21, 2016

CaRuO3 thin films were synthesized on SrTiO3 substrates by pulsed laser deposition. Detailed microstructure analysis by transmission electron microscopy revealed the pseudoheterostructure in CaRuOfilms. It consists of a coherently strained cubic CaRuOlayer contacted with substrate, as well as a strained orthorhombic CaRuO3layer. The orthorhombic CaRuO3layer is composed of two types of domains. The ferromagnetic property of the pseudoheterostructure CaRuO3was revealed by superconducting quantum interference device measurement. This is due to the cubic CaRuO3layer, which is supported by first-principle calculations. The formation mechanism of pseudoheterostructure in ultrathin CaRuO3thin films was proposed.

This paper is published on APL.

Link to the full text: http://apl.aip.org/resource/1/applab/v96/i18/p182502_s1

4 May, 2010

  

 

 

Topological insulators represent a new state of quantum matter recently discovered with insulating bulk but conducting surface states formed by an odd number of Dirac fermions. In this Letter, we report our recent progress on the study of electronic structures of ex-situ grown topological insulator thin films by angle resolved photoemission spectroscopy (ARPES). We successfully obtained the topological band structures of molecular beam epitaxial HgTe and vapor–solid grown Bi2Te3 thin films after proper surface cleaning procedures. This new development will not only enable us to study more topological insulators that cannot be measured by conventional in-situ ARPES technique (e.g. by cleaving or growing samples in-situ), but also open the door to directly characterize the electronic properties of topological insulators used in functional devices.

文章作为封面,发表在physica status solidi-Rapid Research Letters 7, 130 (2013)

全文链接:http://onlinelibrary.wiley.com/doi/10.1002/pssr.201206400/abstract

封面链接:http://onlinelibrary.wiley.com/doi/10.1002/pssr.201390000/abstract

pss

Highly crystalline quality c-axis epitaxial nLaFeO3–Bi4Ti3O12 (n = 0.5,1.0,1.5) thin films were deposited on SrTiO3 (001) substrates by pulsed laser deposition. The x-ray diffraction and transmission electron microscopy characterizations confirm that there are designed even-odd number perovskite-block structures in n = 0.5 and 1.5 films while it has even-even number ones in n = 1.0 films. The remarkable physical property of n = 0.5 and 1.5 samples is the presence of ferrimagnetism even up to room temperature. While it is antiferromagentic property in n = 1.0 sample. The observed ferrimagentism is explained qualitatively by considering the crystal structure in nLaFeO3–Bi4Ti3O12.

This paper is published on APL.

Link to the full text: http://apl.aip.org/resource/1/applab/v98/i21/p212501_s1

23 May, 2011

  

 

 

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