Quantum oscillations without magnetic field

Abstract

When magnetic field B is applied to a metal, nearly all observable quantities exhibit oscillations periodic in 1/B. Such quantum oscillations reflect the fundamental reorganization of electron states into Landau levels as a canonical response of the metal to the applied magnetic field. We predict here that, remarkably, in the recently discovered Dirac and Weyl semimetals quantum oscillations can occur in the complete absence of magnetic field. These zero-field quantum oscillations are driven by elastic strain which, in the space of the low-energy Dirac fermions, acts as a chiral gauge potential. We propose an experimental setup in which the strain in a thin film (or nanowire) can generate pseudomagnetic field b as large as 15T and demonstrate the resulting de Haas-van Alphen and Shubnikov-de Haas oscillations periodic in 1/b.Dirac and Weyl semimetals [1][2][3] are known to exhibit a variety of exotic behaviors owing to their unusual electronic structure comprised of linearly dispersing electron bands at low energies. This includes the pronounced negative magnetoresistance [4][5][6][7][8][9][10][11] attributed to the phenomenon of the chiral anomaly [12][13][14], theoretically predicted nonlocal transport [15,16], Majorana flat bands [17], as well as an unusual type of quantum oscillations (QO) that involve both bulk and topologically protected surface states [18,19]. In this theoretical study we establish a completely new mechanism for QO in Dirac and Weyl semimetals that requires no magnetic field. These zero-field oscillations occur as a function of the applied elastic strain and, similar to the canonical de Haas-van Alphen and Shubnikov-de Haas oscillations [20], manifest themselves as oscillations periodic in 1/b, where b is the strain-induced pseudomagnetic field, in all measurable thermodynamic and transport properties. To the best of our knowledge this is the first instance of such zero-field quantum oscillations in any known substance.Materials with linearly dispersing electrons respond in peculiar ways to the externally imposed elastic strain. In graphene, for instance, the effect of curvature is famously analogous to a pseudomagnetic field [21] that can be quite large and is known to generate pronounced Landau levels observed in the tunneling spectroscopy [22]. Recent theoretical work [23][24][25][26][27] showed that similar effects can be anticipated in three-dimensional Dirac and Weyl semimetals, although the estimated field strengths in the geometries that have been considered are rather small (below 1 Tesla in Ref. [26]). Ordinary quantum oscillations, periodic in 1/B, have already been observed in Dirac semimetals Cd 3 As 2 and Na 3 Bi [19,[28][29][30] but the magnetic field required is B 2T. This, then, would seem to rule out the observation of strain-induced QO in geometries considered previously. We make a key advance in this work by devising a new geometry in which pseudomagnetic field b as large as 15T can be achieved. The proposed setup consists of a thin film (or a nanowire) in which pseudo...

Chiral magnetic plasmons in anomalous relativistic matter

“…Indeed, in Weyl materials, b 0 and b correspond to energy and momentum-space separations between the Weyl nodes, respectively. Strain-induced axial (or, equivalently, pseudoelectromagnetic) fields are described byà 5 ν , which is directly related to the deformation tensor [26][27][28][29][30]33]. As is easy to check, the consistent electric current, i.e.,…”

“…From a physics viewpoint, the pseudoelectromagnetic fields E 5 and B 5 stem from strains in Weyl materials [27,30,33]. The pseudoelectric field E 5 is obtained by dynamically deforming the sample.…”

“…Of course, this is expected in the case of static deformations. The characteristic strengths of the pseudomagnetic field in Dirac and Weyl materials are much smaller than in graphene and range from about B 5 ≈ 0.3 T, when a static torsion is applied to a nanowire of Cd 3 As 2 [30], to approximately B 5 ≈ 15 T, when a thin film of Cd 3 As 2 is bent [33].…”

“…Recently, a different mechanism for quantum oscillations in Dirac and Weyl semimetals without magnetic fields was proposed in Ref. [33]. This mechanism relies on strain-induced pseudomagnetic field B 5 and, similarly to the ordinary quantum oscillations in Weyl semimetals [35], manifests itself as oscillations of the DOS periodic in 1/B 5 .…”

“…As emphasized in Ref. [33], the great tunability of the pseudomagnetic field provides a new and convenient experimental basis for the study of strain induced gauge fields in Weyl materials.…”