Interfacial and bulk polaron masses in Zn1−xMgxO/ZnO heterostructures examined by terahertz time-domain cyclotron spectroscopy

Abstract

The cyclotron resonance of polarons in Zn1−xMgxO/ZnO heterostructures (with 0.15<x<0.22) was studied by terahertz time-domain spectroscopy. Low-temperature magnetoconductivity spectra of the 2D electron gas at the Zn1−xMgxO/ZnO interface determined the polaron density, mass, and scattering rate. The cyclotron mass of 2D polarons was found to increase significantly with magnetic field B from 0.24 me at B = 2 T to 0.37 me at B = 7.5 T. A nonlinear cyclotron frequency with B was also observed for 3D polarons in ZnO. The findings are discussed in the context of polaron mass renormalization driven by the electron-LO-phonon and electron-acoustic phonon interactions.

Colossal Terahertz Magnetoresistance at Room Temperature in Epitaxial La0.7Sr0.3MnO3 Nanocomposites and Single-Phase Thin Films

“…where the THz resistivity ratio changes by nearly three orders of magnitude between 10 K and 300 K, while the dc ratio changes by only a factor of 30. The contrasting temperature dependences of the conductivity may be linked to: (i) dissimilar scattering times probed by THz radiation and transport: the transport lifetime is weighted by an additional geometric factor; 24 (ii) dierent transport masses and optical masses, resulting from the electron-electron interaction, as seen in other polar oxides; 11 (iii) dc and ac conduction arising from distinct physical processes, or probing dierent length scales.…”

“…The magneto-optical response at terahertz (THz) frequencies is a powerful probe of material properties, allowing carrier masses , and spin–orbit coupling strengths to be uncovered for conducting systems. Interesting physical phenomena such as the quantum Hall effect and the giant magnetoresistance of ferromagnetic metals have been found to persist up to THz frequencies.…”

“…The magneto-optical response at THz frequencies is a powerful probe of material properties, allowing carrier masses 10,11 and spin-orbit coupling strengths 12 was found to grow towards the Curie temperature, reaching -99.9 % for the VAN at 300 K, corresponding to a change by more than 2 orders of magnitude in the THz conductivity. In contrast, the dc CMR for VANs peaks below T C .…”

“…The magneto-optical response at terahertz (THz) frequencies is a powerful probe of material properties, allowing carrier masses 10,11 and spin−orbit coupling strengths 12 phenomena such as the quantum Hall effect 13 and the giant magnetoresistance of ferromagnetic metals 14 have been found to persist up to THz frequencies. In metal heterostructures exhibiting giant magnetoresistance, a study of the THz magnetoconductivity found similar THz and dc magnetoresistances with changes of around 20% in the THz conductivity induced by B = 100 mT.…”

Identification and modulation of electronic band structures of single-phase β-(AlxGa1−x)2O3 alloys grown by laser molecular beam epitaxy

“…33 Recently, the effective mass of the 2DEG formed at (Al x Ga 1Àx ) 2 O 3 /Ga 2 O 3 (x ¼ 0.2) interface is estimated to be 0.313 m e , 7 which is related to the strong electron-electron interaction. 34 The electronic band structure and bandgap modulation by Al incorporation can also be evaluated by absorption spectra. Transmittance spectra of b-(Al x Ga 1Àx ) 2 O 3 film samples have been recorded at room temperature and shown in Fig.…”