scholarly journals Metal–insulator-like transition, superconducting dome and topological electronic structure in Ga-doped Re3Ge7

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Yanwei Cui ◽  
Siqi Wu ◽  
Qinqing Zhu ◽  
Guorui Xiao ◽  
Bin Liu ◽  
...  
Keyword(s):  
Phase Transition ◽  
First Principles ◽  
Hole Doping ◽  
First Principles Calculations ◽  
Metal Insulator ◽  
Topological Materials ◽  
Maximum Value ◽  
Fermi Surface Nesting ◽  
Ga Doping ◽  
Rare Opportunity

AbstractSuperconductivity frequently appears by doping compounds that show a collective phase transition. So far, however, this has not been observed in topological materials. Here we report the discovery of superconductivity induced by Ga doping in orthorhombic Re3Ge7, which undergoes a second-order metal–insulator-like transition at ~58 K and is predicted to have a nontrivial band topology. It is found that the substitution of Ga for Ge leads to hole doping in Re3Ge7−xGax. As a consequence, the phase transition is gradually suppressed and disappears above x = 0.2. At this x value, superconductivity emerges and Tc exhibits a dome-like doping dependence with a maximum value of 3.37 K at x = 0.25. First principles calculations suggest that the phase transition in Re3Ge7 is associated with an electronic instability driven by Fermi-surface nesting and the nontrival band topology is preserved after Ga doping. Our results indicate that Ga-doped Re3Ge7 provides a rare opportunity to study the interplay between superconductivity and competing electronic states in a topologically nontrivial system.

Orbital change manipulation metal–insulator transition temperature in W-doped VO2

2015 ◽  
Vol 17 (17) ◽  
pp. 11638-11646 ◽  
Author(s):  
Xinfeng He ◽  
Yijie Zeng ◽  
Xiaofeng Xu ◽  
Congcong Gu ◽  
Fei Chen ◽  
...  
Keyword(s):  
Phase Transition ◽  
Infrared Spectroscopy ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
First Principles ◽  
Insulator Transition ◽  
First Principles Calculations ◽  
Orbital Structure ◽  
Metal Insulator Transition ◽  
Metal Insulator

Using ultraviolet-infrared spectroscopy and first principles calculations, it is revealed that changes in the orbital structure can regulate the W-doped VO2 phase transition temperature.

scholarly journals Interface-induced sign reversal of the anomalous Hall effect in magnetic topological insulator heterostructures

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fei Wang ◽  
Xuepeng Wang ◽  
Yi-Fan Zhao ◽  
Di Xiao ◽  
Ling-Jie Zhou ◽  
...  
Keyword(s):  
Hall Effect ◽  
Electric Fields ◽  
First Principles ◽  
Berry Phase ◽  
Condensed Matter ◽  
Anomalous Hall Effect ◽  
First Principles Calculations ◽  
Sign Reversal ◽  
Berry Curvature ◽  
Topological Materials

AbstractThe Berry phase picture provides important insights into the electronic properties of condensed matter systems. The intrinsic anomalous Hall (AH) effect can be understood as the consequence of non-zero Berry curvature in momentum space. Here, we fabricate TI/magnetic TI heterostructures and find that the sign of the AH effect in the magnetic TI layer can be changed from being positive to negative with increasing the thickness of the top TI layer. Our first-principles calculations show that the built-in electric fields at the TI/magnetic TI interface influence the band structure of the magnetic TI layer, and thus lead to a reconstruction of the Berry curvature in the heterostructure samples. Based on the interface-induced AH effect with a negative sign in TI/V-doped TI bilayer structures, we create an artificial “topological Hall effect”-like feature in the Hall trace of the V-doped TI/TI/Cr-doped TI sandwich heterostructures. Our study provides a new route to create the Berry curvature change in magnetic topological materials that may lead to potential technological applications.

First-principles study on the heterostructure of twisted graphene/hexagonal boron nitride/graphene sandwich structure

2021 ◽  
Author(s):  
Yiheng Chen ◽  
Wen-Ti Guo ◽  
Zi-si Chen ◽  
Suyun Wang ◽  
Jian-Min Zhang
Keyword(s):  
Phase Transition ◽  
Boron Nitride ◽  
Charge Density ◽  
First Principles ◽  
Sandwich Structure ◽  
Hexagonal Boron Nitride ◽  
Mulliken Population ◽  
Metal Insulator ◽  
Insulator Phase Transition ◽  
Twisted Graphene

Abstract In recent years, the discovery of "magic angle" graphene has given new inspiration to the formation of heterojunctions. Similarly, the use of hexagonal boron nitride, known as white graphene, as a substrate for graphene devices has more aroused great interest in the graphene/hexagonal boron nitride (G/hBN) heterostructure system. Based on the first principles method of density functional theory, the band structure, density of states, Mulliken population, and differential charge density of a tightly packed model of twisted graphene/hexagonal boron nitride/graphene (G/hBN/G) sandwich structure have been studied. Through the establishment of heterostructure models TBG inserting hBN with different twisted angles, it was found that the band gap, Mulliken population, and charge density, exhibited specific evolution regulars with the rotation angle of the upper graphene, showing novel electronic properties and realizing metal-insulator phase transition. We find that the particular value of the twist angle at which the metal-insulator phase transition occurs and propose a rotational regulation mechanism with angular periodicity. Our results have guiding significance for the practical application of heterojunction electronic devices.

Bandgap engineering of α-Ga2O3 by hydrostatic, uniaxial, and equibiaxial strain

2021 ◽  
Author(s):  
Takahiro Kawamura ◽  
Toru Akiyama
Keyword(s):  
First Principles ◽  
Compressive Strain ◽  
Correction Method ◽  
Wide Bandgap ◽  
Potential Range ◽  
First Principles Calculations ◽  
Bandgap Engineering ◽  
Wide Bandgap Semiconductor ◽  
Lattice Strains ◽  
Maximum Value

Abstract Ga2O3 is a wide bandgap semiconductor and an understanding of its bandgap tunability is required to broaden the potential range of Ga2O3 applications. In this study, the different bandgaps of α-Ga2O3 were calculated by performing first-principles calculations using the pseudopotential self-interaction correction method. The relationships between these bandgaps and the material's hydrostatic, uniaxial, and equibiaxial lattice strains were investigated. The direct and indirect bandgaps of strain-free α-Ga2O3 were 4.89 eV and 4.68 eV, respectively. These bandgap values changed linearly and negatively as a function of the hydrostatic strain. Under the uniaxial and equibiaxial strain conditions, the maximum bandgap appeared under application of a small compressive strain, and the bandgaps decreased symmetrically with increasing compressive and tensile strain around the maximum value.

scholarly journals Effect of Zn doping on phase transition and electronic structures of Heusler-type Pd2Cr-based alloys: from normal to all-d-metal Heusler

RSC Advances ◽  
2020 ◽  
Vol 10 (30) ◽  
pp. 17829-17835
Author(s):  
Xiaotian Wang ◽  
Mengxin Wu ◽  
Tie Yang ◽  
Rabah Khenata
Keyword(s):  
Phase Transition ◽  
Electronic Structure ◽  
First Principles ◽  
Electronic Structures ◽  
Heusler Alloys ◽  
First Principles Calculations ◽  
Zn Doping

By first-principles calculations, for Heusler alloys Pd2CrZ (Z = Al, Ga, In, Tl, Si, Sn, P, As, Sb, Bi, Se, Te, Zn), the effect of Zn doping on their phase transition and electronic structure has been studied in this work.

scholarly journals Atomic and electronic structures of charge-doping VO2: first-principles calculations

RSC Advances ◽  
2020 ◽  
Vol 10 (32) ◽  
pp. 18543-18552 ◽  
Author(s):  
Lanli Chen ◽  
Yuanyuan Cui ◽  
Hongjie Luo ◽  
Yanfeng Gao
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
First Principles ◽  
Electronic Structures ◽  
First Principles Calculations ◽  
Charge Doping

The controllable phase transition temperature in charge doping VO2 is coupled with changes in the atomic and electronic structures. The current results provide a variable way to tune the VO2 phase transition temperature through charge doping.

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