Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP

Arnold, Frank; Shekhar, Chandra; Wu, Shu-Chun; Sun, Yan; Reis, R. D. dos; Kumar, Nitesh; Naumann, M.; Ajeesh, M. O.; Schmidt, Marcus; Grushin, Adolfo G.; Bardarson, Jens H.; Baenitz, M.; Sokolov, Dmitry; Borrmann, Horst; Nicklas, M.; Felser, Claudia; Hassinger, Elena; Yan, Binghai

doi:10.1038/ncomms11615

Cited by 479 publications

(380 citation statements)

References 56 publications

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“…[46] [40] In this situation, a NLMR may be observed even if the Fermi energy is located far away from the Weyl nodes, and the chirality is not well-defined. [47] In conclusion, we have shown that NLMR results from the anomalous behavior of the lowest bulk Landau level of topological materials (Fig.1) The lowest Landau level N=0 (σ=-1/2) is obtained by solving the inner block Hamiltonian for n = -1. The inner block reduces to:…”

Section: Fig 2 (Color Online) (A)mentioning

confidence: 99%

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials

et al. 2017

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Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and DC field measurements on Pb1-xSnxSe epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N=0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N=0 valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter. [13]. This stems from the helical Dirac nature of surface-states in 3D TIs or, that of edge-states in 2D TIs. In fact, a huge amount of literature (for reviews [14] [15] [16] [17]) took interest in this question and investigated electronic transport of 2D Dirac electrons in 3D-TIs. The majority of these studies were, however, impeded by the significant and dominant bulk transport that occurs in TIs. On the other hand, little attention has been given to signatures of non-trivial band topology in 3D electron transport in a TI.Naively speaking, one can think of the bulk energy bands of a TI as being identical to those of conventional semiconductors and, thus, unlikely to generate non-conventional physical phenomena. However, one should not forget that the basis of a topological insulator lies in the inverted orbital character of these bulk energy bands. [23] shown, that the energy of the lowest (N=0) conduction (valence) Landau level in topological insulators decreases (increases) as a function of increasing magnetic field, opposite to what usually happens in a topologically trivial system ( Fig.1(a,b)). This behavior is anomalous and leads to a field-induced closure of the energy gap in a TI [21] (Fig.1(b)), whereas in a trivial material, the energy gap usually opens with increasing magnetic field ( Fig.1(a)). This anomaly is a hallmark of the inverted band structure of topological materials. Its implications on magnetotransport have not yet been considered. In the present work, we study the MR in topological insulators in the extreme quantum limit -the regime where only the lowest Landau level (LL) is occupied. We measure magnetotransport in pulsed magnetic field up to 61T in high mobility Pb1-xSnxSe epitaxial layers. We show that, when all Lorentz components contributing to the MR are suppressed by applying the magnetic field in-plane and parallel to the excitation current, a negative longitudinal MR (NLMR) emerges near the onset of the quantum limit. This NLMR is only observed in the topological regime of Pb1-xSnxSe (x>0.16) and is absent in trivial samples (x<0.16). We theoretically argue that this NLMR is a result of the anomalous beh...

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Section: Fig 2 (Color Online) (A)mentioning

confidence: 99%

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials

et al. 2017

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“…[10][11][12][13][14] The Weyl semimetal normally exhibits a giant and sometime negative magnetoresistance (MR) due to the semimetal behavior and the opposite spin chirality of the paired Weyl nodes. [15][16][17][18] It is very interesting and highly desired to realize bulk superconductivity in such Weyl semimetals. 19 Previously, Wang et al observed superconducting-like anomaly in the point contact tunneling spectrum on TaAs.…”

Section: Introductionmentioning

confidence: 99%

Concurrence of superconductivity and structure transition in Weyl semimetal TaP under pressure

Zhou

Guo

et al. 2017

npj Quant Mater

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Weyl semimetal defines a material with three-dimensional Dirac cones, which appear in pair due to the breaking of spatial inversion or time reversal symmetry. Superconductivity is the state of quantum condensation of paired electrons. Turning a Weyl semimetal into superconducting state is very important in having some unprecedented discoveries. In this work, by doing resistive measurements on a recently recognized Weyl semimetal TaP under pressures up to about 100 GPa, we show the concurrence of superconductivity and a structure transition at about 70 GPa. It is found that the superconductivity becomes more pronounced when decreasing pressure and retains when the pressure is completely released. High-pressure x-ray diffraction measurements also confirm the structure phase transition from I4 1 md to P-6m2 at about 70 GPa. More importantly, ab-initial calculations reveal that the P-6m2 phase is a new Weyl semimetal phase and has only one set of Weyl points at the same energy level. Our discovery of superconductivity in TaP by high pressure will stimulate investigations on superconductivity and Majorana fermions in Weyl semimetals.

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“…As we did for f 1 , we can define the operatorΘ 0 = −τ eB v 2 k ∂ θ and write f 20 as powers series of the operator (1 +Θ 0 ) −1 applied to the right hand side of (14). To linear order in B, we have, in terms of f 1 :…”

Section: B Kinetic Equation For F20mentioning

confidence: 99%

“…Other observables however, do not appear in Dirac semimetals. Inversion symmetry breaking 9 can partially lift the constraint of having states of opposite chirality at the same point of the Brillouin Zone as it happens in TaAs 10-12 or TaP 13,14 . Time reversal symmetry still forbids some manifestations of the chiral anomaly, like a quantum anomalous Hall current, but the breakdown of inversion symmetry now allows transport and/or optical effects related to the topological structures of the band structure that appear due to the lack of inversion symmetry 15 .…”

Section: Introductionmentioning

confidence: 99%

Magnetic-field-induced nonlinear optical responses in inversion symmetric Dirac semimetals

Cortijo

2016

Phys. Rev. B

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We show that, under the effect of an external magnetic field, a photogalvanic effect and the generation of second harmonic wave can be induced in inversion-symmetric and time reversal invariant Dirac semimetals and it is linear with the magnetic field. The mechanisms responsible of these non linear optical responses is the magnetochiral effect and the chiral magnetic effect. What makes possible that these two effects give rise to the discussed non linear optical effects is the presence of band bending effects in the dispersion relation in real Dirac semimetals. Some observable consequences of this phenomenon are the appearance of a dc current on the surface of the system when it is irradiated with linearly polarized light or a rotation of the polarization plane of the reflected second harmonic wave.

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Negative magnetoresistance without well-defined chirality in the Weyl semimetal TaP

Cited by 479 publications

References 56 publications

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials

Concurrence of superconductivity and structure transition in Weyl semimetal TaP under pressure

Magnetic-field-induced nonlinear optical responses in inversion symmetric Dirac semimetals

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