Low temperature magnetic 2D Majorana and Dirac fermions excitations in La 0.15 Sm 0.85 MnO 3+δ manganites

Abstract

The possibility of excitation of Majorana and massless Dirac fermions in self-doped manganites controlled by an external magnetic field is established. It is shown that in the ZFC mode of magnetization measurement, the excitation of Majorana fermions dominates, while in the FC mode the main contribution to the supermagnetization of the sample is made by the excitation of Dirac fermions. During remagnetization of La0.15Sm0.85MnO3+δ manganites at 4.2 K, the single and double cones-like features of M(H) were found near H = 0 in the magnetization reversal isotherms. These peculiarities of magnetization demonstrate the evolution of the Dirac fermions magnetic excitations at quantum phase transitions in the 2D Dirac semimetal, induced by the merging and splitting of two Dirac points. In the weak magnetic fields H = 100 Oe, 350 Oe and 1 kOe the continuous spectrum of the thermal excitations of spinons in interval temperature 4.2-12 K is divided into three Landau bands with numbers n = 1, n = 2, and n = 3 with two specific features of magnetization M(T) in the shape of alternating double peaks and truncated Dirak cones with different splittings ΔT between components, controlled by external magnetic field and temperature. These new unusual features of magnetic quantum oscillations in La0.15Sm0.85MnO3+δ are characteristic of excitations of 2D Majorana and Dirac fermions in two hidden topological states of chiral spin liquid. PACS: 75.47.Gk, 75.30.Et, 75.30.Kz, 75.47.Lx