arXiv subjects

Dominique Laroche

Publications and source records attributed to Dominique Laroche.

9 recordsLinked to original sources

arXiv2026

Magneto-oscillations, nonlinearity, and nonreciprocity of Coulomb drag in quantum circuits

We consider the problem of Coulomb drag in interactively coupled quantum circuits built of adiabatic constrictions: quantum point contacts and short quantum-wire channels. The interplay of spatial confinement and magnetic field leads to a rich oscillatory response of the drag current as a function of gate voltage and magnetic field: drag peaks track the depopulation of magnetoelectric subbands, are asymptotically periodic in inverse field, and their visibility is controlled by the competition of temperature with the field-sharpened tunneling width of the constriction. We derive a closed expression for the linear drag conductance whose interaction kernel simplifies dramatically in the experimentally relevant limit of a long thermal length compared with the range of the interwire coupling, investigate the drag in the nonlinear regime, where the drag current measures the transconductance of the drive channel at any field, and discuss physically motivated models of dissipation-induced nonreciprocity of the drag signal. Extensions accounting for Zeeman splitting, interaction renormalization of the barrier transmission, backscattering at high field, and the frequency structure of the circuit coupling delineate how each mechanism imprints itself on the temperature dependence and lineshapes of the drag oscillations.

cond-mat.mes-hall↗

arXiv2026

Temperature-driven transition between momentum-resolved and disordered averaged Coulomb drag in 1D systems

Advancing the understanding of electron-electron interactions in one-dimensional systems remains one of the central challenges in low-dimensional physics, especially for Coulomb-coupled Tomonaga-Luttinger liquids. Notably, the difficulty of reliably extracting one-dimensional system parameters, combined with the presence of disorder, has hindered the interpretation of 1D Coulomb drag experiments. Here, we present a self-consistent experimental determination of the relative Luttinger liquid interaction parameters through 1D Coulomb drag measurements, and achieve quantitative agreement with theoretical predictions. Utilizing vertically coupled GaAs-AlGaAs quantum wires, we fully characterize the one-dimensional parameters through magnetic depopulation. Coulomb drag exhibits a systematic evolution with magnetic field, reflecting the successive depopulation of 1D subbands and the suppression of disorder effects. Two distinct temperature regimes are identified, marking the boundary between momentum-resolved and disordered-averaged Coulomb drag. The observed scaling, peak broadening, and nonlinear current-voltage characteristics establish a unified and quantitative framework for probing electron-electron interactions in 1D systems.

cond-mat.mes-hall↗

arXiv2026

Non-reciprocal Coulomb drag in a ballistic quantum wire

1D-Coulomb drag serves as a platform for probing electron-electron interactions in 1D systems. Under the charge fluctuation formalism, the non-reciprocal component of Coulomb drag signal in mesoscopic devices is predicted to rely on the breaking of translational invariance due to intrinsic disorder. In this work, we report the measurement of a Coulomb drag device with a ballistic drag wire, allowing us to study the drag signal in nearly pristine quantum wires. Surprisingly, a non-reciprocal component with strength comparable to that of the reciprocal component is still detected across the measured regime, despite the drag wire being ballistic. We suggest that the non-reciprocal signal arises from low energy disorder in the device, which is consistent with the evolution of the drag wire's conductance at low biases voltages and temperatures. Additionally, the non-reciprocal component of the drag signal shows a power-law temperature dependence that coincides with a diffusive model, while the reciprocal component's temperature dependence cannot be explained under the existing framework. The bias voltage dependence of the drag wire conductance is fitted into three models to extract the interaction parameter and disorder level within the wire, but none of the models provides a fully self-consistent explanation for the data.

cond-mat.mes-hall↗

arXiv2026

Sub-10 mK "In-cell" Magnetic Refrigeration for Cryogen-free Cryostats

A design and implementation of "in-cell" magnetic refrigeration to achieve sub-10 mK temperatures T in cryogen-free dilution refrigerators is presented. The ultra low temperatures below 5 mK are attained in finite magnetic fields B up to 1 T. The holding time below 5 mK varies between about 3 to 30 hours, depending on the final magnetic field after demagnetization process. The developed technique can be used to study low dimensional devices at ultra low electron temperatures in the High B/T regime.

cond-mat.mtrl-sci↗

arXiv2025

Magnetic Field-Enhanced Graphene Superconductivity with Record Pauli-Limit Violation

Spin-polarized superconductors offer a rare platform for studying electronic correlations, but few candidate systems have been experimentally confirmed to date. Here, we report the observation of a spin-polarized superconducting state, denoted SC5, in WSe2-proximitized rhombohedral trilayer graphene. At in-plane magnetic field B|| = 0 T, SC5 has a critical temperature of 68 mK and an out-of-plane critical magnetic field of only 12 mT. Surprisingly, these values are significantly enhanced as B|| increases, and the superconductivity persists to B|| = 8.8 T. This value corresponds to a record-high Pauli-limit violation ratio of at least 80 among all superconductors, while the true critical field is beyond the limit of our instrument. We conclude that SC5 experiences a canting crossover from Ising-type to spin-polarized superconductor with increased B||.

cond-mat.supr-con↗

arXiv2025

Quasi-1D Coulomb drag between spin-polarized quantum wires

One-dimensional (1D) quantum wires provide a versatile platform for studying strong electron-electron interactions and collective excitations under confinement. Coulomb drag between 1D systems offers a powerful probe of Tomonaga-Luttinger liquid (TLL) physics, with theoretical predictions suggesting distinct power-law in temperature dependencies between the spin-full and the spin-polarized regimes. However, experimental verification has thus far remained limited. Here, we report measurements of reciprocal and nonreciprocal Coulomb drag between vertically coupled quasi-1D quantum wires in the spin-polarized regime. Clear signatures of spin splitting are observed in both the wires conductance and the drag signal. We observed a connection between electron-hole asymmetry and negative drag, and demonstrated different power-law behaviors in spin-full and spin-polarized regimes, yielding consistent TLL interaction parameters. These results validate the theoretical predictions for backscattering induced drag in the reciprocal regime and extend them to the nonreciprocal and the multiple subband regimes. Furthermore, the nonmonotonic density dependence of the reciprocal interaction parameter correlates with the subband occupation of the drag wire, revealing the complexity of the scattering mechanisms in multichannel systems.

cond-mat.mes-hall↗

arXiv2024

Quasi-1D Coulomb drag in the nonlinear regime

One-dimensional Coulomb drag has been an essential tool to probe the physics of interacting Tomonaga-Luttinger liquids. To date, most experimental work has focused on the linear regime while the predictions for Luttinger liquids beyond the linear response theory remain largely untested. In this letter, we report measurements of momentum transfer induced Coulomb drag between vertically-coupled quasi-one-dimensional quantum wires in the nonlinear regime. Measurements were performed at ultra-low temperatures between wires only 15 nm apart. Our results reveal a nonlinear dependence of the drag voltage as a function of the drive current superimposed with an oscillatory contribution, in agreement with theoretical predictions for Coulomb drag between Tomonaga-Luttinger liquids. Additionally, the observed current-voltage ($I$-$V$) characteristics exhibit a nonmonotonic temperature dependence, further corroborating the presence of non-Fermi-liquid behavior in our system. These findings are observed both in the single and in the multiple subband regimes and in the presence of disorder, extending the onset of this behavior beyond the clean single channel Tomonaga-Luttinger regime where the predictions were originally formulated.

cond-mat.mes-hall↗

arXiv2020

Observation of the 4$π$-periodic Josephson effect in indium arsenide nanowires

Quantum computation by non-Abelian Majorana zero modes (MZMs) offers an approach to achieve fault tolerance by encoding quantum information in the non-local charge parity states of semiconductor nanowire networks in the topological superconductor regime. Thus far, experimental studies of MZMs chiefly relied on single electron tunneling measurements which leads to decoherence of the quantum information stored in the MZM. As a next step towards topological quantum computation, charge parity conserving experiments based on the Josephson effect are required, which can also help exclude suggested non-topological origins of the zero bias conductance anomaly. Here we report the direct measurement of the Josephson radiation frequency in InAs nanowires with epitaxial aluminium shells. For the first time, we observe the $4π$-periodic Josephson effect above a magnetic field of $\approx 200\,$mT, consistent with the estimated and measured topological phase transition of similar devices.

cond-mat.mes-hall↗

arXiv2020

Broadband microwave spectroscopy of semiconductor nanowire-based Cooper-pair transistors

The Cooper-pair transistor (CPT), a small superconducting island enclosed between two Josephson weak links, is the atomic building block of various superconducting quantum circuits. Utilizing gate-tunable semiconductor channels as weak links, the energy scale associated with the Josephson tunneling can be changed with respect to the charging energy of the island, tuning the extent of its charge fluctuations. Here, we directly demonstrate this control by mapping the energy level structure of a CPT made of an indium arsenide nanowire (NW) with a superconducting aluminum shell. We extract the device parameters based on the exhaustive modeling of the quantum dynamics of the phase-biased nanowire CPT and directly measure the even-odd parity occupation ratio as a function of the device temperature, relevant for superconducting and prospective topological qubits.

cond-mat.mes-hall↗