Structure and Lattice Dynamics of R $$_2$$ 2 Sn $$_2$$ 2 O $$_7$$ 7 and R $$_2$$ 2 Zr $$_2$$ 2 O $$_7$$ 7 (R = La–Lu) Crystals: Ab Initio Calculation

Journal of Superconductivity and Novel Magnetism - Crystal structure and phonon spectrum of rare-earth stannates R $$_2$$ Sn $$_2$$ O $$_7$$ and zirconates R $$_2$$ Zr $$_2$$ O $$_7$$ (R =...     

First-principles Investigations on the Magnetic,Electronic, and Optical Properties of Honeycomb-Kagome-Structured Fe $$_{2}$$ O $$_3$$ Monolayer

Journal of Superconductivity and Novel Magnetism - Two-dimensional materials with a novel honeycomb-kagome structure have got a variety of attentions owing to their dramatic properties. In the...     

Electronic and Magnetic Properties of the BaTiO $$_{3}$$ 3 /LaMnO $$_{3}$$ 3 Interface: a DFT Study

Journal of Superconductivity and Novel Magnetism - The electronic and magnetic properties of the BaTiO $$_{3}$$ /LaMnO $$_{3}$$ interface were investigated by means of ab initio calculations within...     

Synthesis and Magnetic Properties of TNb $$_3$$ S $$_6$$ (T = Co,Ni, Cu)

Journal of Superconductivity and Novel Magnetism - We have studied the magnetic properties of transition metal intercalated niobium dichalcogenides CoNb $$_3$$ S $$_6$$ , NiNb $$_3$$ S $$_6$$ and...     

Physical Properties of Antiferromagnetic Dirac Semimetal SrMnSb $$_{2}$$

Journal of Superconductivity and Novel Magnetism - We have prepared high-quality nearly stoichiometric single crystal of Dirac semimetal SrMnSb $$_{2}$$ and systematically investigated the physical...     

Phase Transition and Superconductivity Enhancement in Se‐Substituted MoTe2 Thin Films

Consecutively tailoring few‐layer transition metal dichalcogenides MX₂ from 2H to T_d phase may realize the long‐sought topological superconductivity in a single material system by incorporating superconductivity and the quantum spin Hall effect together. Here, this study demonstrates that a consecutive structural phase transition from T_d to 1T′ to 2H polytype can be realized by increasing the Se concentration in Se‐substituted MoTe₂ thin films. More importantly, the Se‐substitution is found to dramatically enhance the superconductivity of the MoTe₂ thin film, which is interpreted as the introduction of two‐band superconductivity. The chemical‐constituent‐induced phase transition offers a new strategy to study the s^+? superconductivity and the possible topological superconductivity, as well as to develop phase‐sensitive devices based on MX₂ materials.     

Ab initio Insight of the Electronic,Structural, Mechanical and Optical Properties of X $$_3$$ 3 P $$_2$$ 2 (X= Mg,Ca) from GGA and Hybrid Functional (HSE06)

Journal of Superconductivity and Novel Magnetism - In this paper, the structural, mechanical and optoelectronic properties of X $$_3$$ P $$_2$$ (X= Mg, Ca) have been investigated by using the...     

Aspects of Topological Superconductivity in 2D Systems: Noncollinear Magnetism,Skyrmions, and Higher-order Topology

Journal of Superconductivity and Novel Magnetism - The review is aimed at highlighting the aspects of topological superconductivity in the absence of spin–orbit interaction in two-dimensional...     

Discovery of Superconductivity in 2M WS2 with Possible Topological Surface States

Recently the metastable 1T′‐type VIB‐group transition metal dichalcogenides (TMDs) have attracted extensive attention due to their rich and intriguing physical properties, including superconductivity, valleytronics physics, and topological physics. Here, a new layered WS₂ dubbed “2M” WS₂, is constructed from 1T′ WS₂ monolayers, is synthesized. Its phase is defined as 2M based on the number of layers in each unit cell and the subordinate crystallographic system. Intrinsic superconductivity is observed in 2M WS₂ with a transition temperature T_c of 8.8 K, which is the highest among TMDs not subject to any fine‐tuning process. Furthermore, the electronic structure of 2M WS₂ is found by Shubnikov–de Haas oscillations and first‐principles calculations to have a strong anisotropy. In addition, topological surface states with a single Dirac cone, protected by topological invariant Z₂, are predicted through first‐principles calculations. These findings reveal that the new 2M WS₂ might be an interesting topological superconductor candidate from the VIB‐group transition metal dichalcogenides.     

Interfacial Superconductivity on the Topological Semimetal Tungsten Carbide Induced by Metal Deposition

Interfaces between materials with different electronic ground states have become powerful platforms for creating and controlling novel quantum states of matter, in which inversion symmetry breaking and other effects at the interface may introduce additional electronic states. Among the emergent phenomena, superconductivity is of particular interest. Here, by depositing metal films on a newly identified topological semimetal tungsten carbide (WC) single crystal, interfacial superconductivity is obtained, evidenced from soft point-contact spectroscopy. This very robust phenomenon is demonstrated for a wide range of metal/WC interfaces, involving both nonmagnetic and ferromagnetic films, and the superconducting transition temperatures are surprisingly insensitive to the magnetism of thin films. This method offers an opportunity to explore the long-sought topological superconductivity and has potential applications in topological-state-based spin devices.     

Superconductivity of Topological Surface States and Strong Proximity Effect in Sn1−xPbxTe–Pb Heterostructures

Superconducting topological crystalline insulators are expected to form a new type of topological superconductors to host Majorana zero modes under the protection of lattice symmetries. The bulk superconductivity of topological crystalline insulators can be induced through chemical doping and the proximity effect. However, only conventional full gaps are observed, so the existence of topological superconductivity in topological crystalline insulators is still controversial. Here, the successful fabrication of atomically flat lateral and vertical Sn_1?xPb_xTe–Pb heterostructures by molecular beam epitaxy is reported. The superconductivity of the Sn_1?xPb_xTe–Pb heterostructures can be directly investigated by scanning tunneling spectroscopy. Unconventional peak–dip–hump gap features and fourfold symmetric quasiparticle interference patterns taken at the zero energy in the superconducting gap support the presence of the topological superconductivity in superconducting Sn_1?xPb_xTe. Strong superconducting proximity effect and easy preparation of various constructions between Sn_1?xPb_xTe and Pb make the heterostructures to be a promising candidate for topological superconducting devices to detect and manipulate Majorana zero modes in the future.     

Caustic Pattern of Magnetoelastic Waves in the Vicinity of Magnetoelastic Resonance in Fe $$_{1-x}$$ 1 - x Ga $$_{x}$$ x Crystal

Journal of Superconductivity and Novel Magnetism - The vicinities of two resonance points where longitudinal and transverse elastic waves interact with the magnetic mode are considered. The caustic...     

Superconductivity in (Bi,Pb)2Ca2Sr2Cu3−xVxOy

The superconducting properties of V-doped (Bi,Pb)2Sr2Ca2Cu3Oy (2223) samples have been investigated by means of X-ray diffraction and electrical resistivity measurements. The volume fraction of the 2223 phase decreases with a decrease in the c lattice parameter. The onset of superconductivity in the samples remains almost constant while the temperature at which the resistivity becomes zero decreases with increasing dopant content. The electrical resistivity data suggest that the substitution of copper by vanadium suppresses the superconductivity in (Bi,Pb)2Sr2Ca2Cu3–xVxOy by destroying the phase coherence and by pair-breaking effects. The suppression of superconductivity in the system could also be due to a decrease in the carrier concentration.     

Van der Waals heterostructures based on three-dimensional topological insulators

Three-dimensional (3D) topological insulators (TIs) have generated tremendous research interest over the past decade due to their topologically-protected surface states with linear dispersion and helical spin texture. The topological surface states offer an important platform to realize topological phase transitions, topological magnetoelectric effects and topological superconductivity via 3D TI-based heterostructures. In this review, we summarize the key findings of magneto and quantum transport properties in 3D TIs and their related heterostructures with normal insulators, ferromagnets and superconductors. For intrinsic 3D TIs, the experimental evidences of the topological surface states and their coupling effects are reviewed. Whereas for 3D TI related heterostructures, we focus on some important phenomenological magnetotransport activities and provide explanations for the proximity-induced topological and quantum effects.     

On‐Chip Andreev Devices: Hard Superconducting Gap and Quantum Transport in Ballistic Nb–In0.75Ga0.25As‐Quantum‐Well–Nb Josephson Junctions

A superconducting hard gap in hybrid superconductor–semiconductor devices has been found to be necessary to access topological superconductivity that hosts Majorana modes (non‐Abelian excitation). This requires the formation of homogeneous and barrier‐free interfaces between the superconductor and semiconductor. Here, a new platform is reported for topological superconductivity based on hybrid Nb–In_0.75Ga_0.25As‐quantum‐well–Nb that results in hard superconducting gap detection in symmetric, planar, and ballistic Josephson junctions. It is shown that with careful etching, sputtered Nb films can make high‐quality and transparent contacts to the In_0.75Ga_0.25As quantum well, and the differential resistance and critical current measurements of these devices are discussed as a function of temperature and magnetic field. It is demonstrated that proximity‐induced superconductivity in the In_0.75Ga_0.25As‐quantum‐well 2D electron gas results in the detection of a hard gap in four out of seven junctions on a chip with critical current values of up to 0.2 µA and transmission probabilities of >0.96. The results, together with the large g ‐factor and Rashba spin–orbit coupling in In_0.75Ga_0.25As quantum wells, which indeed can be tuned by the indium composition, suggest that the Nb–In_0.75Ga_0.25As–Nb system can be an excellent candidate to achieve topological phase and to realize hybrid topological superconducting devices.     

Decompression‐Driven Superconductivity Enhancement in In2Se3

An unexpected superconductivity enhancement is reported in decompressed In₂Se₃. The onset of superconductivity in In₂Se₃ occurs at 41.3 GPa with a critical temperature (T_c) of 3.7 K, peaking at 47.1 GPa. The striking observation shows that this layered chalcogenide remains superconducting in decompression down to 10.7 GPa. More surprisingly, the highest T_c that occurs at lower decompression pressures is 8.2 K, a twofold increase in the same crystal structure as in compression. It is found that the evolution of T_c is driven by the pressure‐induced R‐3m to I‐43d structural transition and significant softening of phonons and gentle variation of carrier concentration combined in the pressure quench. The novel decompression‐induced superconductivity enhancement implies that it is possible to maintain pressure‐induced superconductivity at lower or even ambient pressures with better superconducting performance.     

Current-Induced Metastable States Close to T $$_{c}$$ c in NbTi Superconducting Bridges

Journal of Superconductivity and Novel Magnetism - We have studied the characteristics of different metastable states in NbTi thin film deposited on sapphire substrate in a region very close to the...     

Flat Band in Topological Matter

Topological media are systems whose properties are protected by topology, and thus are robust to deformations of the system. In topological insulators and superconductors, the bulk-surface and bulk-vortex correspondence gives rise to the gapless Weyl, Dirac, or Majorana fermions on the surface of the system and inside vortex cores. In gapless topological media, the bulk-surface and bulk-vortex correspondence produce topologically protected gapless fermions without dispersion—the flat band. Fermion zero modes forming the flat band are localized on the surface of topological media with protected nodal lines and in the vortex core in systems with topologically protected Fermi points (Weyl points). Flat band has an extremely singular density of states, and this property may give rise in particular to surface superconductivity, which in principle could exist even at room temperature.     

Subperoxide Model for Tc Onset in Cell Volume Expanded Orthorhombics in Y1−xGdxBa2Cu3Oy

Title compounds stabilize superconducting orthorhombic cell volume (V) expanded varieties. Conventional V contracted alternate chain orthorhombics are absent near y=65. The arrisal of superconductivity with y with slight expansion rather than pronounced V shrinkage obviates conventional charge transfer and supports selfdoping on a subperoxide model for superconductivity.     

A Possible 2D H x WO3 Superconductor with a T c of 120 K

Magnetic susceptibility measurements of WO₃ crystals hydrogen doped on the surface suggest 2D local non-percolated superconductivity with an onset temperature of 120 K. Observed zero field cooled vs. field cooled magnetization response is characteristic of type II superconductivity. The diamagnetic response at the critical temperature is field dependent, and is suppressed by a magnetic field of ∼1700 Oe.