arXiv subjects

Gillian E. Minarik

Publications and source records attributed to Gillian E. Minarik.

4 recordsLinked to original sources

arXiv2026

Candidate for a Fractional Topological Insulator in Twisted MoTe2

The interplay among electronic correlation, topology, and time-reversal-symmetry (TRS) often leads to exotic quantum states of matter, as highlighted by the discoveries of fractional Chern insulators (FCIs) in twisted bilayer MoTe2 (tMoTe2). Among the FCIs in tMoTe2, the most robust is at a hole filling factor of v=-2/3 per moiré unit cell. Here, employing pump-probe circular dichroism (CD) measurement on tMoTe2 at twist angles (3.9 and 3.7 degrees), we show that a correlated state at v =-4/3 exhibits an unusual Ising antiferromagnet behavior. The v =-4/3 state with no net magnetization undergoes first order phase transitions at extremely low magnetic fields of ~ 2-6 mT to partially valley polarized (PVP) states. This behavior is notably absent for all other correlated states in tMoTe2 and also disappears for v =-4/3 at higher or lower twist angles (4.0 or 3.3 degree). The observed magnetic signature is consistent with a theoretically proposed fractional topological insulator (FTI), consisting of two copies of v =-2/3 FCIs with opposite chirality in the two K valleys. The experimental results are supported by interacting continuum model calculations that reveal the extreme closeness in energy ( < 1 meV) between the putative FTI and PVP states. Our findings present a candidate FTI with TRS and call for advanced transport and imaging measurements to establish the quantized helical edge modes.

cond-mat.str-el↗

arXiv2025

Rydberg Exciton Dynamics in the Blockade Regime of Cu2O

Hosting giant Rydberg excitons with principal quantum numbers up to n = 30, cuprous oxide (Cu2O) provides a rare solid-state setting for exploring Rydberg physics, as exemplified by the blockade effect. Here we access the strongly interaction regime at high excitation densities (10^14-10^16/cm^3) and resolve the corresponding blockade dynamics for n = 2-7 using time-resolved spectroscopy. We find that Rydberg blockades are primarily governed by resonant dipolar interactions and that exciton recombination is coupled to the blockade itself. These findings demonstrate the potential for manipulating Rydberg exctions in the strongly interacting blockade regime in a solid state system.

cond-mat.other↗

arXiv2025

Observing the Birth of Rydberg Exciton Fermi Polarons on a Moire Fermi Sea

The optical spectra of two-dimensional (2D) semiconductors are dominated by tightly bound excitons and trions. In the low doping limit, trions are often described as three-body quasiparticles consisting of two electrons and one hole or vice versa. However, trions are more rigorously understood as quasiparticles arising from the interaction between an exciton and excitation of the Fermi sea - referred to as exciton Fermi polaron. Here we employ pump-probe spectroscopy to directly observe the formation of exciton Fermi polarons in a model system composed of a WSe2 monolayer adjacent to twisted bilayer graphene (tBLG). Following the pump-injection of Rydberg excitons in WSe2, a time-delayed probe pulse tracks the development of Rydberg exciton Fermi polarons as interactions with localized carriers in the tBLG moire superlattice evolve. Both the exciton Fermi polaron relaxation rate and binding energy are found to increase with electron or hole density. Our findings provide insight into the optical response of fundamental excitations in 2D Van der Waals systems and reveal how many-body interactions give rise to emergent quasiparticles.

cond-mat.mes-hall↗

arXiv2022

Spin-state Directed Synthesis of >20 micrometers 2D Layered Transition Metal Hydroxides via Edge-on Condensation

Layered transition metal hydroxides (LTMHs) with transition metal centers sandwiched between layers of coordinating hydroxide anions have attracted considerable interest for their potential in developing clean energy sources and storage technologies. However, two dimensional (2D) LTMHs remain largely unstudied in terms of their physical properties and the applications in electronic devices. Here, directed by the relationship of the spin state of 3d transition metal (TM) ions such as Ni, Co, Cu, and the corresponding geometry of the crystal field, we discover that Ni2+ with perfect Oh symmetry is ideal for intraplanar growth, leading to the achievement of >20 μm α-Ni(OH)2 2D crystals with high yield, which are the largest 2D domains reported so far. We also report the successful synthesis of 2D Co(OH)2 crystals (>40 μm) with less yield due to the slight geometry distortion resulted from uneven number of electrons. Moreover, the detailed structural characterization of synthesized α-Ni(OH)2 are performed; the optical band gap energy is extrapolated as 2.54 eV from optical absorption measurements and is measured as 2.50 eV from reflected electrons energy loss spectroscopy (REELS), suggesting the potential as insulating 2D dielectric material for electronic devices. Furthermore, key parameters of the hydrothermal reaction including soaking temperature, starting pH and cooling rate, are systematically tuned to understand their effects on morphological and crystallographic perspectives, allowing the establishment of a 2D growth mechanism. This work demonstrates a scalable pathway to synthesize large 2D LTMHs from simple methods, paving the way for the study of fundamental physical properties and device applications of 2D LTMHs.

cond-mat.mtrl-sci↗