Phonon assisted resonant tunneling and its phonons control

The current-voltage characteristics of a new range of devices built around Weyl semimetals has been predicted using the Landauer formalism. The potential step and barrier have been reconsidered for three-dimensional Weyl semimetals, with analogies to the two-dimensional material graphene and to optics. With the use of our results we also show how a Veselago lens can be made from Weyl semimetals, e.g., from NbAs and NbP. Such a lens may have many practical applications and can be used as a probing tip in a scanning tunneling microscope (STM). The ballistic character of Weyl fermion transport inside the semimetal tip, combined with the ideal focusing of the Weyl fermions (by Veselago lens) on the surface of the tip may create a very narrow electron beam from the tip to the surface of the studied material. With a Weyl semimetal probing tip the resolution of the present STMs can be improved significantly, and one may image not only individual atoms but also individual electron orbitals or chemical bonding and therewith to resolve the long-term issue of chemical and hydrogen bond formation. We show that applying a pressure to the Weyl semimental, having no center of spatial inversion, one may model matter at extreme conditions, such as those arising in the vicinity of a black hole. As the materials Cd 3 As 2 and Na 3 Bi show an asymmetry in their Dirac cones, a scaling factor was used to model this asymmetry. The scaling factor created additional regions of no propagation and condensed the appearance of resonances. We argue that under an external pressure there may arise a topological phase transition in Weyl semimetals, where the electron transport changes character and becomes anisotropic. There a hyperbolic Dirac phase occurs where there is a strong light absorption and photocurrent generation.

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“…The results obtained in graphene are equally applicable to a broad class of materials generally named topological insulators 4,5 . In Ref.…”

Section: Introductionmentioning

confidence: 73%

“…In Ref. 4 it was shown that on the interface between the two insulating semiconductors CdTe and HgTe(Se) an inverted band structure may arise. The inverted band structure creates a metallic conducting layer associated with the Dirac gapless spectrum.…”

Section: Introductionmentioning

confidence: 99%

Current-voltage characteristics of Weyl semimetal semiconducting devices, Veselago lenses, and hyperbolic Dirac phase

2017

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“…In combination with our previous work on this system [16,19], we conclude that the three dimensional spin-orbit interaction induced by oxygen impurities is essential to the significant isotropic enhancement of B c2 . The effects of oxygen impurities could be general in oxides, thus providing us new clues to generate other exotic phenomena such as Ising superconductivity [14,35], topological nontrivial state due to band inversion [36][37][38], vortex phase transition from liquid to solid [39].…”

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confidence: 99%

Anomalies of upper critical field in the spinel superconductor LiTi2O4−δ

Wei

et al. 2019

Phys. Rev. B

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High-field electrical transport and point-contact tunneling spectroscopy were used to investigate superconducting properties of the unique spinel oxide, LiTi 2 O 4−δ films with various oxygen content. We find that the upper critical field B c2 gradually increases as more oxygen impurities are brought into the samples by carefully tuning the deposition atmosphere. It is striking that although the superconducting transition temperature and energy gap are almost unchanged, an astonishing isotropic B c2 up to ∼ 26 Tesla is observed in oxygenrich sample, which is doubled compared to the anoxic sample and breaks the Pauli limit.Such anomalies of B c2 were rarely reported in other three dimensional superconductors.Combined with all the anomalies, three dimensional spin-orbit interaction induced by tiny oxygen impurities is naturally proposed to account for the remarkable enhancement of B c2 in oxygen-rich LiTi 2 O 4−δ films. Such mechanism could be general and therefore provides ideas for optimizing practical superconductors with higher B c2 .In this letter, we present systematic transport measurements and point-contact tunneling spectroscopy study of LiTi 2 O 4−δ films with various oxygen content. For oxygen-rich samples, a significantly enhanced B c2 up to 26 T at low temperatures is observed. Such doubled B c2 , compared with anoxic samples, is isotropic. Intriguingly, superconducting energy gap and T c are almost the same for all samples. Temperature-dependent B c2 can be well fitted by the Werthamer-Helfand-Hohenberg (WHH) theory considering spin paramagnetism and spin-orbit scattering[20], yet it leads to an underestimation of relaxation time for oxygen-rich samples. Here we consider the three dimensional spin-orbit interaction induced by oxygen impurities, which is beyond the WHH theory, thereby giving an universal understanding of the enhancement of B c2 and other anomalies.High-quality LiTi 2 O 4−δ thin films were epitaxially grown on MgAl 2 O 4 (001) substrates by pulsed laser deposition under various oxygen pressures from basic vacuum (< 1 × 10 −6 Torr) to ∼ 5 × 10 −6 Torr [19]. The temperature-and field-dependence of resistance were measured by a standard four-probe method in PPMS-16T, and steady high magnetic field facility with field up to 33 T. Point-contact measurements were performed by employing a homemade probe using Pt/Ir

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“…The TCCM was extensively studied using either bosonization [8][9][10][11][12][13] or RG [14][15][16][17][18][19][20] methods. The first studies considered only some of the scattering processes produced by forward like couplings associated with the interband and the intraband interactions.…”

Section: Introductionmentioning

confidence: 99%

Fermi surface renormalization and quantum confinement in the two-coupled chains model

Correa

Ferraz

2014

Eur. Phys. J. B

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Abstract. We address the problem of the Fermi surface renormalization and the quantum confinement regime (QCR) in the two coupled chains model(TCCM) of spinless fermions. We perform a self-consistent calculation of the renormalization group(RG) flows of the renormalized TCCM couplings and quasiparticle weight. On top of that we take explicitly into account the renormalization of the Fermi surface. The flow of the difference of the renormalized Fermi wave vectors associated with the bonding and antibonding bands has a dramatic effect on the single particle spectrum. Although the quasiparticle amplitude is nullified already at intermediate coupling the QCR is only observed at strong coupling. The state associated with this regime has a charge gap and it is not a Luttinger liquid. In contrast, the Fermi liquid regime is stabilized by the umklapp "g2-like" interactions at very weak coupling regime.

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Phonon assisted resonant tunneling and its phonons control

Cited by 13 publications

References 23 publications

Current-voltage characteristics of Weyl semimetal semiconducting devices, Veselago lenses, and hyperbolic Dirac phase

Current-voltage characteristics of Weyl semimetal semiconducting devices, Veselago lenses, and hyperbolic Dirac phase

Anomalies of upper critical field in the spinel superconductor LiTi2O4−δ

Fermi surface renormalization and quantum confinement in the two-coupled chains model

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