Temperature-driven massless Kane fermions in HgCdTe crystals

Abstract

It has recently been shown that electronic states in bulk gapless HgCdTe offer another realization of pseudo-relativistic three-dimensional particles in condensed matter systems. These single valley relativistic states, massless Kane fermions, cannot be described by any other relativistic particles. Furthermore, the HgCdTe band structure can be continuously tailored by modifying cadmium content or temperature. At critical concentration or temperature, the bandgap collapses as the system undergoes a semimetal-to-semiconductor topological phase transition between the inverted and normal alignments. Here, using far-infrared magneto-spectroscopy we explore the continuous evolution of band structure of bulk HgCdTe as temperature is tuned across the topological phase transition. We demonstrate that the rest mass of Kane fermions changes sign at critical temperature, whereas their velocity remains constant. The velocity universal value of (1.07±0.05) × 106 m s−1 remains valid in a broad range of temperatures and Cd concentrations, indicating a striking universality of the pseudo-relativistic description of the Kane fermions in HgCdTe.

Two-Dimensional Massless Dirac Fermions in Antiferromagnetic AFe2As2 Chen1, Wang2, Song3 et al. 2017Phys. Rev. Lett.286220View full textAdd to dashboardCite

“…Therefore, massless fermions, which are characterized by band-degeneracy points and linear energy-momentum dispersions, are expected to exist in the AFM state of BaFe 2 As 2 [19,20,25,[28][29][30][31][32][33][34]. There are three types of massless fermions, including MDF, massless Kane fermions, and Weyl fermions [35][36][37][38][39][40][41][42]. Therein, massless Kane fermions and Weyl fermions are characterized by a heavy-hole valence band around the…”

Geometric valley Hall effect and valley filtering through a singular Berry flux

“…For instance, there exists a correspondence between our model and massless Kane fermion systems 50,51 that can arise in 3D zinc-blende crystals, i.e., Hg 1−x Cd x Te, at some critical doping concentration [52][53][54] . In particular, for singular Berry flux Φ = 1/2 (α = 1/ √ 3), we have…”

“…In recent experiments [52][53][54] , exotic Dirac-like quasiparticles named massless Kane fermions have been observed in 3D zinc-blende crystals, i.e., Hg 1−x Cd x Te, at some critical doping concentration. In the presence of strong spin-orbit interaction (e.g., ∼ 1eV), the fermions can be effectively described by the six-band Kane Hamiltonian…”

Symmetry breaking and circular photogalvanic effect in epitaxial CdxHg1−xTe films

“…In the case of bulk Cd x Hg 1 -x Te crystals the formation of helical surface states becomes possible due to the fact that the proper choice of the amount of Cadmium in the alloy yields an inversion of the band ordering, see e.g. [17,19,34]. Furthermore, in materials with low x the band structure can be changed from normal to inverted band ordering simply by a variation of the temperature, T [19].…”