scholarly journals Emergence of topological superconductivity in doped topological Dirac semimetals under symmetry-lowering lattice distortions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sangmo Cheon ◽  
Ki Hoon Lee ◽  
Suk Bum Chung ◽  
Bohm-Jung Yang
Keyword(s):  
Bound States ◽  
Unconventional Superconductivity ◽  
Zero Bias ◽  
Dirac Semimetal ◽  
Orbital Electron ◽  
Lattice Distortions ◽  
Topological Semimetals ◽  
Superconducting Pairing ◽  
And Control ◽  
Topological Superconductivity

AbstractRecently, unconventional superconductivity having a zero-bias conductance peak is reported in doped topological Dirac semimetal (DSM) with lattice distortion. Motivated by the experiments, we theoretically study the possible symmetry-lowering lattice distortions and their effects on the emergence of unconventional superconductivity in doped topological DSM. We find four types of symmetry-lowering lattice distortions that reproduce the crystal symmetries relevant to experiments from the group-theoretical analysis. Considering inter-orbital and intra-orbital electron density-density interactions, we calculate superconducting phase diagrams. We find that the lattice distortions can induce unconventional superconductivity hosting gapless surface Andreev bound states (SABS). Depending on the lattice distortions and superconducting pairing interactions, the unconventional inversion-odd-parity superconductivity can be either topological nodal superconductivity hosting a flat SABS or topological crystalline superconductivity hosting a gapless SABS. Remarkably, the lattice distortions increase the superconducting critical temperature, which is consistent with the experiments. Our work opens a pathway to explore and control pressure-induced topological superconductivity in doped topological semimetals.

scholarly journals Skyrmion control of Majorana states in planar Josephson junctions

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Narayan Mohanta ◽  
Satoshi Okamoto ◽  
Elbio Dagotto
Keyword(s):  
Josephson Junctions ◽  
Bound States ◽  
Spin Orbit Coupling ◽  
Majorana Bound States ◽  
Rashba Spin ◽  
Dimensional Electron Gas ◽  
And Control ◽  
Zero Phase ◽  
Additional Phase ◽  
Topological Superconductivity

AbstractPlanar Josephson junctions provide a versatile platform, alternative to the nanowire-based geometry, for the generation of the Majorana bound states, due to the additional phase tunability of the topological superconductivity. The proximity induction of chiral magnetism and superconductivity in a two-dimensional electron gas showed remarkable promise to manipulate topological superconductivity. Here, we consider a Josephson junction involving a skyrmion crystal and show that the chiral magnetism of the skyrmions can create and control the Majorana bound states without the requirement of an intrinsic Rashba spin-orbit coupling. Interestingly, the Majorana bound states in our geometry are realized robustly at zero phase difference at the junction. The skyrmion radius, being externally tunable by a magnetic field or a magnetic anisotropy, brings a unique control feature for the Majorana bound states.

scholarly journals Skyrmion Control of Majorana States in Planar Josephson Junctions

2021 ◽  
Author(s):  
Narayan Mohanta ◽  
Satoshi Okamoto ◽  
Elbio Dagotto
Keyword(s):  
Josephson Junctions ◽  
Bound States ◽  
Spin Orbit Coupling ◽  
Majorana Bound States ◽  
Rashba Spin ◽  
Dimensional Electron Gas ◽  
And Control ◽  
Zero Phase ◽  
Additional Phase ◽  
Topological Superconductivity

Abstract Planar Josephson junctions provide a versatile platform, alternative to the nanowire-based geometry, for the generation of the Majorana bound states, due to the additional phase tunability of the topological superconductivity. The proximity induction of chiral magnetism and superconductivity in a two-dimensional electron gas showed remarkable promises to manipulate topological superconductivity. Here, we consider a Josephson junction involving a skyrmion crystal and show that the chiral magnetism of the skyrmions can create and control the Majorana bound states without the requirement of an intrinsic Rashba spin-orbit coupling. Interestingly, the Majorana bound states in our geometry are realized robustly at zero phase difference at the junction. The skyrmion radius, being externally tunable by a magnetic field or a magnetic anisotropy, brings a unique control feature for the Majorana bound states.

scholarly journals Topological isoconductance signatures in Majorana nanowires

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
L. S. Ricco ◽  
J. E. Sanches ◽  
Y. Marques ◽  
M. de Souza ◽  
M. S. Figueira ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Transport Properties ◽  
Spin Polarization ◽  
Bound States ◽  
Spin Asymmetry ◽  
Experimental Protocol ◽  
Zero Bias ◽  
Topological Superconductor ◽  
Hybrid Device ◽  
Majorana Bound States

AbstractWe consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. It is demonstrated that if highly nonlocal and nonoverlapping MBSs are formed in the system, the zero-bias Andreev conductance through the dot exhibits characteristic isoconductance profiles with the shape depending on the spin asymmetry of the coupling between the dot and the topological superconductor. Otherwise, for overlapping MBSs with less degree of nonlocality, the conductance is insensitive to the spin polarization and the isoconductance signatures disappear. This allows to propose an alternative experimental protocol for probing the nonlocality of the MBSs in Majorana nanowires.

scholarly journals Observation and control of the weak topological insulator state in ZrTe5

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Peng Zhang ◽  
Ryo Noguchi ◽  
Kenta Kuroda ◽  
Chun Lin ◽  
Kaishu Kawaguchi ◽  
...  
Keyword(s):  
Band Gap ◽  
Topological Insulator ◽  
Spin Current ◽  
Side Surface ◽  
Quantum Spin ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Dirac Semimetal ◽  
Topological States ◽  
The One ◽  
And Control

AbstractA quantum spin Hall (QSH) insulator hosts topological states at the one-dimensional (1D) edge, along which backscattering by nonmagnetic impurities is strictly prohibited. Its 3D analogue, a weak topological insulator (WTI), possesses similar quasi-1D topological states confined at side surfaces. The enhanced confinement could provide a route for dissipationless current and better advantages for applications relative to strong topological insulators (STIs). However, the topological side surface is usually not cleavable and is thus hard to observe. Here, we visualize the topological states of the WTI candidate ZrTe5 by spin and angle-resolved photoemission spectroscopy (ARPES): a quasi-1D band with spin-momentum locking was revealed on the side surface. We further demonstrate that the bulk band gap is controlled by external strain, realizing a more stable WTI state or an ideal Dirac semimetal (DS) state. The highly directional spin-current and the tunable band gap in ZrTe5 will provide an excellent platform for applications.

scholarly journals Observation and control of maximal Chern numbers in a chiral topological semimetal

Science ◽  
2020 ◽  
Vol 369 (6500) ◽  
pp. 179-183 ◽  
Author(s):  
Niels B. M. Schröter ◽  
Samuel Stolz ◽  
Kaustuv Manna ◽  
Fernando de Juan ◽  
Maia G. Vergniory ◽  
...  
Keyword(s):  
Topological Invariant ◽  
Chern Number ◽  
Linear Dispersion ◽  
Fermi Arc ◽  
Number Magnitude ◽  
Fermi Arcs ◽  
Chern Numbers ◽  
Topological Semimetals ◽  
Chiral Crystals ◽  
And Control

Topological semimetals feature protected nodal band degeneracies characterized by a topological invariant known as the Chern number (C). Nodal band crossings with linear dispersion are expected to have at most |C|=4, which sets an upper limit to the magnitude of many topological phenomena in these materials. Here, we show that the chiral crystal palladium gallium (PdGa) displays multifold band crossings, which are connected by exactly four surface Fermi arcs, thus proving that they carry the maximal Chern number magnitude of 4. By comparing two enantiomers, we observe a reversal of their Fermi-arc velocities, which demonstrates that the handedness of chiral crystals can be used to control the sign of their Chern numbers.

scholarly journals Особенности поведения ионов Mn-=SUP=-2+-=/SUP=- в 3D-дираковском полуметалле alpha-Cd-=SUB=-3-=/SUB=-As-=SUB=-2-=/SUB=- по данным ЭПР

2021 ◽  
Vol 63 (2) ◽  
pp. 199
Author(s):  
Ю.В. Горюнов ◽  
А.Н. Натепров
Keyword(s):  
Magnetic Field ◽  
Free Electron ◽  
Bound States ◽  
High Manganese ◽  
Contact Potential ◽  
Conduction Electrons ◽  
Europium Doping ◽  
Dirac Semimetal ◽  
Electromagnetic Measurements ◽  
The Magnetic Field

The behavior of the manganese impurity in the 3D Dirac semimetal Cd3As2 has been studied by EPR and electromagnetic measurements. It was found that, in contrast to doping with europium, doping with manganese, as well as with iron, does not lead to a change in the sign of the magnetoresistance, which is almost completely suppressed at high manganese concentrations. In this case, a change in the type of the influence of the magnetic field on the contact potential is manifested. The g-factors measured in EPR coincide with the g-factor of a free electron at all temperatures, which, taking into account the fluctuation behavior of the EPR linewidth and the reduced magnetic moment on Mn2 +, indicates the formation of short-lived bound states of the Mn2 + ion and conduction electrons - antiferromagnetic polarons.

scholarly journals Disorder-induced suppression of the zero-bias conductance peak splitting in topological superconducting nanowires

2018 ◽  
Vol 9 ◽  
pp. 1358-1369 ◽  
Author(s):  
Jun-Tong Ren ◽  
Hai-Feng Lü ◽  
Sha-Sha Ke ◽  
Yong Guo ◽  
Huai-Wu Zhang
Keyword(s):  
Bound States ◽  
Chemical Potential ◽  
Zero Mode ◽  
Tight Binding ◽  
Fano Factor ◽  
Energy Splitting ◽  
Binding Model ◽  
Superconducting Nanowires ◽  
Zero Bias ◽  
Conductance Peak

We investigate the effect of three types of intrinsic disorder, including that in pairing energy, chemical potential, and hopping amplitude, on the transport properties through the superconducting nanowires with Majorana bound states (MBSs). The conductance and the noise Fano factor are calculated based on a tight-binding model by adopting a non-equilibrium Green’s function method. It is found that the disorder can effectively lead to a reduction in the conductance peak spacings and significantly suppress the peak height. Remarkably, for a longer nanowire, the zero-bias peak could be reproduced by weak disorder for a finite Majorana energy splitting. It is interesting that the shot noise provides a signature to discriminate whether the zero-bias peak is induced by Majorana zero mode or disorder. For Majorana zero mode, the noise Fano factor approaches zero in the low bias voltage limit due to the resonant Andreev tunneling. However, the Fano factor is finite in the case of a disorder-induced zero-bias peak.

Novel Material Shows Unconventional Superconductivity with Magnetic Order Under Pressure

2021 ◽  
Vol 1 ◽  
Keyword(s):  
Triplet State ◽  
Magnetic Order ◽  
Degree Of Freedom ◽  
Quantum Computers ◽  
Unconventional Superconductivity ◽  
The Novel ◽  
Spin Degree ◽  
Novel Material ◽  
Spin Triplet ◽  
Topological Superconductivity

Multiple superconductivity wad found in the novel spin-triplet superconductor UTe<sub>2</sub>, which is called "Silicon of Quantum Computers". A complicated spin-triplet state is realized as a consequence of spin degree of freedom. This result will lead to a new state of topological superconductivity.

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