Proximity induced band gap opening in topological-magnetic heterostructure (Ni80Fe20/p-TlBiSe2/p-Si) under ambient condition

Abstract

The broken time reversal symmetry states may result in the opening of a band gap in TlBiSe₂ leading to several interesting phenomena which are potentially relevant for spintronic applications. In this work, the quantum interference and magnetic proximity effects have been studied in Ni₈₀Fe₂₀/p-TlBiSe₂/p-Si (Magnetic/TI) heterostructure using physical vapor deposition technique. Raman analysis shows the symmetry breaking with the appearance of A²_1u mode. The electrical characteristics are investigated under dark and illumination conditions in the absence as well as in the presence of a magnetic field. The outcomes of the examined device reveal excellent photo response in both forward and reverse bias regions. Interestingly, under a magnetic field, the device shows a reduction in electrical conductivity at ambient conditions due to the crossover of weak localization and separation of weak antilocalization, which are experimentally confirmed by magnetoresistance measurement. Further, the photo response has also been assessed by the transient absorption spectroscopy through analysis of charge transfer and carrier relaxation mechanisms. Our results can be beneficial for quantum computation and further study of topological insulator/ferromagnet heterostructure and topological material based spintronic devices due to high spin orbit coupling along with dissipationless conduction channels at the surface states.

Figure 1

The Raman spectra. (a) p-TlBiSe₂/p-Si heterojunction (b) p-TlBiSe₂/Ni₈₀Fe₂₀/p-Si heterojunction.

Figure 2

Ultrafast transient absorption spectra of p-TlBiSe₂/Ni₈₀Fe₂₀/p-Si film from 400 to 800 nm wavelength in AMF and PMF. (a, b) show the ultrafast surface of examined heterostructure while corresponding insets represent TlBiSe₂ band structure in AMF and PMF, respectively. (c, d) show TA spectra with varying probe delay in AMF and PMF, respectively. (e, f) show kinetic profiles in AMF and PMF, respectively. ( The representation of the heterostructure for this characterization is shown as Fig. 8 in experimental section).

Figure 3

Dark characteristics of p-TlBiSe₂/p-Si heterostructure at room temperature in AMF and PMF. (a, b) show the photocurrent density vs. voltage (J–V) plot and magnified semi-log characteristics plot, while the inset shows the resistance voltage (R–V) plot in AMF and PMF, respectively. (c, d) show the semi-log (I) vs V characteristics in AMF and PMF respectively. (e, f) shows the forward biased linearly fitted plot of $\frac{\mathit{dV}}{d\left(l,n,I\right)}$ vs. I while the corresponding inset shows the ($\frac{\mathit{dV}}{\mathit{dI}})$ vs V characteristics, showing the exponential relation of the slope with applied voltage in AMF and PMF, respectively. (The representation of the heterostructure for this measurement is shown as Fig. 7 in experimental section).

Figure 4

Schematic showing the generation of spin–orbit coupling and spin–orbit torque (SOT) in Ni₈₀Fe₂₀/p-TlBiSe₂.

Figure 5

(a) MR vs. magnetic field plot for various currents. (b) Schematic of the band gap opening in TI due to TRS breaking. (c, d, e) shows the room temperature MOKE hysteresis loops of p-Si, Ni₈₀Fe₂₀ and Ni₈₀Fe₂₀/p-TlBiSe₂/p-Si, respectively. While the inset of (e) shows the cross–sectional view of Ni₈₀Fe₂₀/p-TlBiSe₂.

Figure 6

Schematic of the energy band diagram of the Ni₈₀Fe₂₀/p-TlBiSe₂/p-Si heterostructure. (a) In AMF, under forward bias with light illumination resulting an increase in forward current. (b) In PMF, under forward bias with light illumination resulting decline in current due to TRS breaking in TI material.

Figure 7

Schematic of Ni₈₀Fe₂₀/p-TlBiSe₂/p-Si heterostructure in presence and absence of magnetic field respectively.

Figure 8

Schematic of TlBiSe_2/Ni₈₀Fe₂₀/p-Si heterostructure in presence and absence of magnetic field respectively.