Thomas Markus Ihn


Last Name

Ihn

First Name

Thomas Markus

ORCID

0000-0002-5587-6953

Organisational unit

03439 - Ensslin, Klaus / Ensslin, Klaus

Search Results

Publications1 - 10 of 122
  • Transport Through a Network of Topological Channels in Twisted Bilayer Graphene
    Item type: Journal Article
    Rickhaus, Peter; Wallbank, John; Slizovskiy, Sergey; et al. (2018)
    Nano Letters
  • High-mobility transport in isotopically enriched ¹²C and ¹³C exfoliated graphene
    Item type: Journal Article
    Iwakiri, Shuichi; Miller, Jakob; Lang, Florian; et al. (2023)
    Physical Review Research
    Graphene quantum dots are promising candidates for qubits due to weak spin-orbit and hyperfine interactions. The hyperfine interaction, controllable via isotopic purification, could be the key to further improving the coherence. Here, we use isotopically enriched graphite crystals of both ¹²C and ¹³C grown by a high-pressure-high-temperature method to exfoliate graphene layers. We fabricated Hall bar devices and performed quantum transport measurements, revealing mobilities exceeding 10⁵ cm² /V s and a long mean free path of microns, which are as high as natural graphene. Shubnikov–de Haas oscillations, quantum Hall effect up to the filling factor of one, and Brown-Zak oscillations due to the alignment of hBN and graphene are observed thanks to the high mobility. These results constitute a material platform for physics and engineering of isotopically enriched graphene qubits.
  • Electronic g factor and magnetotransport in InSb quantum wells
    Item type: Journal Article
    Lei, Zijin; Lehner, Christian A.; Rubi, Km; et al. (2020)
    Physical Review Research
    High mobility InSb quantum wells with tunable carrier densities are investigated by transport experiments in magnetic fields tilted with respect to the sample normal. We employ the coincidence method and the temperature dependence of the Shubnikov–de Haas oscillations and find a value for the effective g factor of |g^∗| = 35±4 and a value for the effective mass of m^∗ ≈ 0.017 m_e, where m_e is the free electron mass. Our measurements are performed in a magnetic field and a density range where the enhancement mechanism of the effective g factor can be neglected. Accordingly, the obtained effective g factor and the effective mass can be explained in a single-particle picture. Additionally, we explore the magnetotransport up to magnetic fields of 35 T and do not find features related to the fractional quantum Hall effect.
  • Spin-Selective Equilibration among Integer Quantum Hall Edge Channels
    Item type: Journal Article
    Nicoli, Giorgio; Adam, Christoph; Röösli, Marc P.; et al. (2022)
    Physical Review Letters
    The equilibration between quantum Hall edge modes is known to depend on the disorder potential and the steepness of the edge. Modern samples with higher mobilities and setups with lower electron temperatures call for a further exploration of the topic. We develop a framework to systematically measure and analyze the equilibration of many (up to 8) integer edge modes. Our results show that spin-selective coupling dominates even for non-neighboring channels with parallel spin. Changes in magnetic field and bulk density let us control the equilibration until it is almost completely suppressed and dominated only by individual microscopic scatterers. This method could serve as a guideline to investigate and design improved devices, and to study fractional and other exotic states.
  • Quantum dot with internal substructure
    Item type: Conference Paper
    Graf, Davy; Ihn, Thomas Markus; Ensslin, Klaus; et al. (2007)
    AIP Conference Proceedings ~ Physics of Semiconductors: 28th International Conference on the Physics of Semiconductors - ICPS 2006
    We report the fabrication and measurement of a finite‐periode lateral superlattice within a Coulomb blockaded island, thereby creating a quantum dot with a periodic internal substructure. The potential modulation introduces an additional length scale to the quantum dot state, which can be probed with a perpendicular magnetic field.
  • Electronic properties of C doped (100) AlGaAs heterostructures
    Item type: Conference Paper
    Grbić, Boris; Ellenberger, Christoph; Ihn, Thomas Markus; et al. (2005)
    AIP Conference Proceedings ~ Physics of Semiconductors: 27th International Conference on the Physics of Semiconductors - ICPS-27
    Carbon doped p‐type AlGaAs heterostructures are investigated by low‐temperature magnetotransport measurements. High quality of such two dimensional hole gases is demonstrated by observing sharp integer plateaus in Hall resistance as well as features of fractional quantum Hall effect at filling factors 4/3 and 5/3. The observed beating pattern of low‐field Shubnikov‐de Haas oscillations represents clear evidence for the existence of the two spin‐split subbands which arise from strong spin‐orbit coupling in hole systems.
  • Entropy Spectroscopy of a Bilayer Graphene Quantum Dot
    Item type: Journal Article
    Adam, Christoph; Duprez, Hadrien; Lehmann, Natalie; et al. (2025)
    Physical Review Letters
    We measure the entropy change of charge transitions in an electrostatically defined quantum dot in bilayer graphene. Entropy provides insights into the equilibrium thermodynamic properties of both ground and excited states beyond transport measurements. For the one-carrier regime, the obtained entropy shows that the ground state has a twofold degeneracy lifted by an out-of-plane magnetic field. This observation is in agreement with previous direct transport measurements and confirms the applicability of this novel method. For the two-carrier regime, the extracted entropy indicates a nondegenerate ground state at zero magnetic field, contrary to previous studies suggesting a threefold degeneracy. We attribute the degeneracy lifting to the effect of Kane-Mele-type spin-orbit interaction on the two-carrier ground state, which has not been observed before. Our Letter demonstrates the validity and efficacy of entropy measurements as a unique, supplementary experimental tool to investigate the degeneracy of the ground state in quantum devices built in materials such as graphene. This technique, applied to exotic systems with fractional ground state entropies, will be a powerful tool in the study of quantum matter.
  • Gate-Tunable Hole Transport in In-Plane Ge Nanowires by V-Groove Confined Selective Epitaxy
    Item type: Journal Article
    Ramanandan, Santhanu Panikar; Morelle, Alban; Masseroni, Michele; et al. (2025)
    Advanced Functional Materials
    Germanium (Ge) nanowires hold great promise as building blocks for hole spin-based quantum processors. Realizing this potential requires their direct integration onto silicon (Si) wafers. This work introduces V-groove-confined selective epitaxy to enable the in-plane growth of nanowires on Si substrates. Nanowires form fully confined within V-shaped grooves, a process driven by surface energy minimization and in agreement with Winterbottom-like construction calculations. This confinement eliminates the direct Ge-SiO2 interface, reducing spurring charge noise and enhancing nanowire functionality. Aberration-corrected scanning transmission electron microscopy reveals the cross-sectional shape and single-crystalline nature of the nanowires. Low-temperature magnetotransport measurements on Ge nanowire Hall bars demonstrate gate-tunable hole densities and a peak mobility of approximately 600 cm(2) V(-1)s(-1) at a density of 1.2 x 10(13) cm(-2). These findings establish V-groove-confined epitaxy as a scalable pathway for the integration of high-performance Ge nanowire-based quantum devices.
  • Fano effect in a ring-dot system with tunable coupling
    Item type: Other Conference Item
    Fuhrer, Andreas; Brunsheim, P.; Ihn, Thomas Markus; et al. (2007)
    AIP Conference Proceedings ~ Physics of Semiconductors: 28th International Conference on the Physics of Semiconductors - ICPS 2006
    The interplay between the Fano effect and the Aharonov‐Bohm effect has been studied in a system where a Coulomb‐blockaded quantum dot is side‐coupled to an open quantum ring. The Fano resonance lineshapes observed in the current through the ring can be tuned with an external magnetic field penetrating the ring area and the corresponding Fano‐parameter q is found to be periodic with the Aharonov‐Bohm period of the ring.
  • Fabry-Pérot Interference in Gapped Bilayer Graphene with Broken Anti-Klein Tunneling
    Item type: Journal Article
    Varlet, Anastasia; Liu, Ming-Hao; Krueckl, Viktor; et al. (2014)
    Physical Review Letters
    We report the experimental observation of Fabry-Pérot interference in the conductance of a gate-defined cavity in a dual-gated bilayer graphene device. The high quality of the bilayer graphene flake, combined with the device’s electrical robustness provided by the encapsulation between two hexagonal boron nitride layers, allows us to observe ballistic phase-coherent transport through a 1 − μ m -long cavity. We confirm the origin of the observed interference pattern by comparing to tight-binding calculations accounting for the gate-tunable band gap. The good agreement between experiment and theory, free of tuning parameters, further verifies that a gap opens in our device. The gap is shown to destroy the perfect reflection for electrons traversing the barrier with normal incidence (anti-Klein tunneling). The broken anti-Klein tunneling implies that the Berry phase, which is found to vary with the gate voltages, is always involved in the Fabry-Pérot oscillations regardless of the magnetic field, in sharp contrast with single-layer graphene.
Publications1 - 10 of 122