arXiv subjects

Xinchen He

Publications and source records attributed to Xinchen He.

3 recordsLinked to original sources

arXiv2026

Growth and fabrication of advanced PbTe-Pb quantum devices

We report recent progress in the growth and fabrication of advanced PbTe-Pb Majorana devices for three-terminal correlation experiments. A critical prerequisite for these devices is a continuous Pb film spanning from the PbTe nanowire to the substrate. In previous studies, PbTe nanowires were spatially separated from the substrate mask, making them unable to fulfill this requirement. To address this issue, we have developed a new growth and fabrication approach. Key fabrication steps are introduced between the PbTe growth and Pb deposition. The top facet of the PbTe nanowire is covered with a Te capping layer before breaking the ultra-high vacuum, enabling ex situ processing for subsequent steps. The mask is then removed, followed by the fabrication of shadow walls. After reloading the chip into the growth chamber, the Te protection layer is removed through thermal decomposition, and the Pb film is subsequently deposited. Notably, a pristine PbTe-Pb interface with an in-situ-equivalent quality can be achieved despite the ex-situ processing. Our technique facilitates the develop of advanced PbTe-Pb quantum devices with complex designs, paving the way toward the realization of topological qubits.

cond-mat.mes-hall↗

arXiv2026

From Ground State to Electronic and Vibronic Spectra via Memory Kernel Coupling Theory and Neural Quantum States

Modelling molecular absorption spectra from scalable ground-state representations is challenging because conventional approaches often require explicit excited states or time propagation. Here, we introduce a method to obtain Absorption Using Recursive Operator Response with vibronic Augmentation (Aurora), which combines neural quantum states (NQSs) with continued-fraction memory-kernel coupling theory (CF-MKCT). Aurora maps the zero-temperature Liouvillian response hierarchy onto repeated wavefunction-space applications of a shifted Hamiltonian to a dipole-prepared state, enabling direct spectral reconstruction from variational ground states. The implementation combines variational Monte Carlo, implicit-restarted-Lanczos-assisted NQS optimization, matrix-free Hamiltonian application, and adaptive recursion control. The resulting electronic spectra closely agree with full-configuration-interaction and conventional MKCT references for tractable molecules, with the restarted-Lanczos strategy improving difficult NQS cases. For electron-phonon Hamiltonians, Aurora combines Huang-Rhys mode selection with local singular-value-decomposition (SVD) phonon encoders. The H2 benchmark indicates that compression retains the dominant vibronic envelope and improves upon bare local-basis truncation, while paired calculations for N2, H2O, H2S, and NH3 yield similar principal features with and without encoding. We further obtain vibronic spectra for C6H6 and a 10-electron, 10-orbital C10H8 active space. Overall, Aurora provides a unified route from variational molecular ground states to electronic and vibronic spectra without constructing excited-state manifolds.

physics.chem-ph↗

arXiv2026

Presence versus absence of charging energies in PbTe quantum dots

Charging energy ($E_C$) is essential in quantum dot (QD) devices. Previous studies on PbTe QDs have reported both the presence and absence of $E_C$. To resolve this ambiguity, we vary the QD size, i.e. the cross-sectional area of PbTe nanowires, and track the evolution of $E_C$. For large crosssectional areas ($\sim$ 16000 nm$^2$), the PbTe QDs exhibit no measurable $E_C$, while quantized levels are well resolved. Decreasing this area successively to 5000, 1500, and 460 nm$^2$, $E_C$ becomes finite and increases to 80, 160, and 210 $μ$eV, respectively. We further demonstrate the strong tunability of local gates, which can tune the PbTe device from the QD regime to the regime of ballistic transport. These results address concerns regarding the large dielectric constant of PbTe and provide key insights in engineering advanced PbTe quantum devices.

cond-mat.mes-hall↗