Two dimensional electron gases (2DEGs) in InAs quantum wells proximitized by aluminum are promising platforms for topological qubits based on Majorana zero modes. However, there are still substantial uncertainties associated with the nature of electronic states at the interface of these systems. It is challenging to probe the properties of these hybridized states as they are buried under a relatively thick aluminum layer. In this work, we have investigated a range of InAs/In1−xGaxAs heterostructures with Al overlayers using high precision time-domain THz spectroscopy (TDTS). Despite the thick metallic overlayer, we observe a prominent cyclotron resonance in a magnetic field that can be associated with the response of the interfacial states. Measurements of the THz range complex Faraday rotation allow the extraction of the sign and magnitude of the effective mass, density of charge carriers, and scattering times of the 2DEG despite the close proximity of the aluminum layer. We discuss the extracted band parameters and connect their values to the known physics of these materials.
References
1.
P. F.
Hopkins
, A. J.
Rimberg
, R. M.
Westervelt
, G.
Tuttle
, and H.
Kroemer
, “Quantum Hall effect in InAs/AlSb quantum wells
,” Appl. Phys. Lett.
58
, 1428
–1430
(1991
).2.
Y.
Ikebe
, T.
Morimoto
, R.
Masutomi
, T.
Okamoto
, H.
Aoki
, and R.
Shimano
, “Optical Hall effect in the integer quantum Hall regime
,” Phys. Rev. Lett.
104
, 256802
(2010
).3.
B.
Spivak
, S. V.
Kravchenko
, S. A.
Kivelson
, and X. P. A.
Gao
, “Colloquium: Transport in strongly correlated two dimensional electron fluids
,” Rev. Mod. Phys.
82
, 1743
–1766
(2010
).4.
J.
Shabani
, M.
Kjærgaard
, H. J.
Suominen
, Y.
Kim
, F.
Nichele
, K.
Pakrouski
, T.
Stankevic
, R. M.
Lutchyn
, P.
Krogstrup
, R.
Feidenhans
et al., “Two-dimensional epitaxial superconductor-semiconductor heterostructures: A platform for topological superconducting networks
,” Phys. Rev. B
93
, 155402
(2016
).5.
R. M.
Lutchyn
, J. D.
Sau
, and D.
Sarma
, “Majorana fermions and a topological phase transition in semiconductor-superconductor heterostructures
,” Phys. Rev. Lett.
105
, 077001
(2010
).6.
Y.
Oreg
, G.
Refael
, and F.
von Oppen
, “Helical liquids and Majorana bound states in quantum wires
,” Phys. Rev. Lett.
105
, 177002
(2010
).7.
W.
Chang
, S. M.
Albrecht
, T. S.
Jespersen
, F.
Kuemmeth
, P.
Krogstrup
, J.
Nygård
, and C. M.
Marcus
, “Hard gap in epitaxial semiconductor-superconductor nanowires
,” Nat. Nanotechnol.
10
, 232
–236
(2015
).8.
M.
Kjaergaard
, F.
Nichele
, H. J.
Suominen
, M. P.
Nowak
, M.
Wimmer
, A. R.
Akhmerov
, J. A.
Folk
, K.
Flensberg
, J.
Shabani
, C. J.
Palmstrøm
, and C. M.
Marcus
, “Quantized conductance doubling and hard gap in a two-dimensional semiconductor-superconductor heterostructure
,” Nat. Commun.
7
, 12841
(2016
).9.
F.
Nichele
, A. C. C.
Drachmann
, A. M.
Whiticar
, E. C. T.
O'Farrell
, H. J.
Suominen
, A.
Fornieri
, T.
Wang
, G. C.
Gardner
, C.
Thomas
, A. T.
Hatke
, P.
Krogstrup
, M. J.
Manfra
, K.
Flensberg
, and C. M.
Marcus
, “Scaling of Majorana zero-bias conductance peaks
,” Phys. Rev. Lett.
119
, 136803
(2017
).10.
M.
Pendharkar
, B.
Zhang
, H.
Wu
, A.
Zarassi
, P.
Zhang
, C. P.
Dempsey
, J. S.
Lee
, S. D.
Harrington
, G.
Badawy
, S.
Gazibegovic
, R. L. M.
Op Het Veld
, M.
Rossi
, J.
Jung
, A.-H.
Chen
, M. A.
Verheijen
, M.
Hocevar
, E. P. A. M.
Bakkers
, C. J.
Palmstrøm
, and S. M.
Frolov
, “Parity-preserving and magnetic field-resilient superconductivity in InSb nanowires with Sn shells
,” Science
372
, 508
–511
(2021
).11.
D. J.
Carrad
, M.
Bjergfelt
, T.
Kanne
, M.
Aagesen
, F.
Krizek
, E. M.
Fiordaliso
, E.
Johnson
, J.
Nygård
, and T. S.
Jespersen
, “Shadow epitaxy for in situ growth of generic semiconductor/superconductor hybrids
,” Adv. Mater.
32
, 1908411
(2020
).12.
T.
Kanne
, M.
Marnauza
, D.
Olsteins
, D. J.
Carrad
, J. E.
Sestoft
, J.
de Bruijckere
, L.
Zeng
, E.
Johnson
, E.
Olsson
, K.
Grove-Rasmussen
, and J.
Nygård
, “Epitaxial Pb on InAs nanowires for quantum devices
,” Nat. Nanotechnol.
16
, 776
–781
(2021
).13.
A. C. C.
Drachmann
, R. E.
Diaz
, C.
Thomas
, H. J.
Suominen
, A. M.
Whiticar
, A.
Fornieri
, S.
Gronin
, T.
Wang
, G. C.
Gardner
, A. R.
Hamilton
, F.
Nichele
, M. J.
Manfra
, and C. M.
Marcus
, “Anodic oxidation of epitaxial superconductor-semiconductor hybrids
,” Phys. Rev. Mater.
5
, 013805
(2021
).14.
R. M.
Lutchyn
, E. P.
Bakkers
, L. P.
Kouwenhoven
, P.
Krogstrup
, C. M.
Marcus
, and Y.
Oreg
, “Majorana zero modes in superconductor–semiconductor heterostructures
,” Nat. Rev. Mater.
3
, 52
–68
(2018
).15.
S.
Schuwalow
, N. B.
Schröter
, J.
Gukelberger
, C.
Thomas
, V.
Strocov
, J.
Gamble
, A.
Chikina
, M.
Caputo
, J.
Krieger
, G. C.
Gardner
et al., “Band structure extraction at hybrid narrow-gap semiconductor–metal interfaces
,” Adv. Sci.
8
, 2003087
(2021
).16.
B.
Cheng
, P.
Taylor
, P.
Folkes
, C.
Rong
, and N.
Armitage
, “Magnetoterahertz response and Faraday rotation from massive Dirac fermions in the topological crystalline insulator Pb0.5Sn0.5Te
,” Phys. Rev. Lett.
122
, 097401
(2019
).17.
C.
Baumgartner
, L.
Fuchs
, L.
Frész
, S.
Reinhardt
, S.
Gronin
, G. C.
Gardner
, M. J.
Manfra
, N.
Paradiso
, and C.
Strunk
, “Josephson inductance as a probe for highly ballistic semiconductor-superconductor weak links
,” Phys. Rev. Lett.
126
, 037001
(2021
).18.
In the thin film limit, the conductance can be extracted using the equation, . Here, is the complex conductance in the eigenbasis of the transmission, n is the refractive index of the substrate, Z0 is the vacuum impedance, and is the thickness difference between the sample and reference substrates.
19.
B.
Cheng
, Y.
Wang
, D.
Barbalas
, T.
Higo
, S.
Nakatsuji
, and N. P.
Armitage
, “Terahertz conductivity of the magnetic Weyl semimetal Mn3Sn films
,” Appl. Phys. Lett.
115
, 012405
(2019
).20.
C. M.
Morris
, R. V.
Aguilar
, A. V.
Stier
, and N. P.
Armitage
, “Polarization modulation time-domain terahertz polarimetry
,” Opt. Express
20
, 12303
–12317
(2012
).21.
N.
Armitage
, “Constraints on Jones transmission matrices from time-reversal invariance and discrete spatial symmetries
,” Phys. Rev. B
90
, 035135
(2014
).22.
L.
Wu
, W.-K.
Tse
, M.
Brahlek
, C. M.
Morris
, R. V.
Aguilar
, N.
Koirala
, S.
Oh
, and N. P.
Armitage
, “High-resolution Faraday rotation and electron-phonon coupling in surface states of the bulk-insulating topological insulator
,” Phys. Rev. Lett.
115
, 217602
(2015
).23.
B. A.
Foreman
, “Elimination of spurious solutions from eight-band theory
,” Phys. Rev. B
56
, R12748
–R12751
(1997
).24.
R.
Winkler
, Spin-Orbit Coupling Effects in Two-Dimensional Electron and Hole Systems
, Springer Tracts in Modern Physics (Springer
, 2003
), Vol. 191
.25.
I.
Vurgaftman
, J. R.
Meyer
, and L. R.
Ram-Mohan
, “Band parameters for III–V compound semiconductors and their alloys
,” J. Appl. Phys.
89
, 5815
–5875
(2001
).26.
27.
S.-W.
Lin
, Y.-H.
Wu
, L.
Chang
, C.-T.
Liang
, and S.-D.
Lin
, “Pure electron-electron dephasing in percolative aluminum ultrathin film grown by molecular beam epitaxy
,” Nanoscale Res. Lett.
10
, 71
(2015
).28.
R.
Skolasinski
et al., see https://gitlab.kwant-project.org/semicon/semicon for for information about the semicon package used for modeling the quantum well and the barrier layers with k.p model.29.
C. W.
Groth
, M.
Wimmer
, A. R.
Akhmerov
, and X.
Waintal
, “Kwant: A software package for quantum transport
,” New J. Phys.
16
, 063065
(2014
).© 2022 Author(s). Published under an exclusive license by AIP Publishing.
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