arXiv subjects

Shumin Guo

Publications and source records attributed to Shumin Guo.

4 recordsLinked to original sources

arXiv2026

Metal hydrides achieve high-Tc superconductivity at low pressure by mimicking high-pressure H3S chemical bonding

Compressed hydrides are promising candidates for high-temperature superconductivity, yet achieving simultaneous structural stability and high-Tc at low pressures remains challenging. Here, we introduce a new mechanism for accomplishing this goal by mimicking the bonding characteristics of high-pressure H3S within metal hydrides. Using Li3CuH4 as an example, its Cu-H covalent interaction effectively mimics the core function of the S-H bonding in H3S. This interaction not only induces a high hydrogen-derived electronic density of states at the Fermi level, but also softens the hydrogen phonon modes, thereby significantly enhancing the electron-phonon coupling. Furthermore, embedding the strongly ionic Li3H lattice into the covalent Cu-H framework stabilizes the structure at significantly low pressures via a chemical-template effect, while maintaining high-Tc. Li3CuH4 exhibits excellent thermodynamic stability at 20 GPa, with a Tc of 39.25 K at 12 GPa. Further comprehensive high-throughput studies on Li3MH4 (M = transition metal) compounds uncover general principles applicable to a broader range of compounds. This work establishes a new paradigm for the simultaneous optimization of the stability and high-temperature superconductivity of metal hydrides through complementary sublattice interactions, thus advancing the search for practical and viable superconducting materials.

cond-mat.supr-con↗

arXiv2025

Mechanisms driving robust high-temperature superconductivity in complex metal hydrides under moderate pressure

The discovery of near-room-temperature superconductivity in compressed hydrides has sparked intensive research efforts to identify superconducting hydrides stable at low or even ambient pressures. Herein, we demonstrate a new mechanism for achieving robust superconductivity in complex metal hydrides under moderate pressure, using Li3IrH9 as a paradigmatic example. This compound displays unique electronic structural characteristics where the broadening and overlap between antibonding electronic bands of [IrH8]2- and adjacent H- orbitals not only drive the intrinsic metallicity of the hydrogen sublattice, generating hydrogen-dominated electronic states at the Fermi level, but also soften hydrogen-related optical phonon modes, inducing strong electron-phonon coupling that remains robust even under high-pressures. First-principles calculations predict that Li3IrH9 maintains thermodynamic stability at 100 GPa while exhibiting a consistently high Tc exceeding 100 K across a broad pressure range (8-150 GPa). Through high-throughput computational screening, we have identified a new superconducting family based on this structural prototype, including Li3RhH9 (Tc = 124 K at 20 GPa) and Li3CoH9 (Tc = 80 K at 10 GPa). This work provides a new platform and original theoretical insights for the development of complex metal hydride superconductors that exhibit robust high-temperature superconductivity and promising practical applications.

cond-mat.supr-con↗

arXiv2024

Modulation of the Octahedral Structure and Potential Superconductivity of La$_3$Ni$_2$O$_7$ through Strain Engineering

The recent transport measurement of La$_3$Ni$_2$O$_7$ uncover a "right-triangle" shape of the superconducting dome in the pressure-temperature (P-T) phase diagram. Motivated by this, we perform theoretical first-principles studies of La$_3$Ni$_2$O$_7$ with the pressure ranging from 0 to 100 GPa. Notably, we reveal a pressure dependence of the Ni-$d_{z^2}$ electron density at the Fermi energy ($n_z^{EF}$) that highly coincides with such shape. On this basis, we further explore the electronic structure under uniaxial stress. By tracking the stress response of $n_z^{EF}$, we propose that superconductivity can be achieved by applying only about 2 GPa of compression along the c axis. The idea is further exemplified from the perspectives of lattice distortion, band structure, Fermi surface and superconducting phase coherence. We also discuss the possible charge modulation under the stress and provide an insight to the relation between n_z^EF and the superconducting Tc in La$_3$Ni$_2$O$_7$ system. Our study provides a helpful guide to the future experiment.

cond-mat.supr-con↗

arXiv2013

Building Confidential and Efficient Query Services in the Cloud with RASP Data Perturbation

With the wide deployment of public cloud computing infrastructures, using clouds to host data query services has become an appealing solution for the advantages on scalability and cost-saving. However, some data might be sensitive that the data owner does not want to move to the cloud unless the data confidentiality and query privacy are guaranteed. On the other hand, a secured query service should still provide efficient query processing and significantly reduce the in-house workload to fully realize the benefits of cloud computing. We propose the RASP data perturbation method to provide secure and efficient range query and kNN query services for protected data in the cloud. The RASP data perturbation method combines order preserving encryption, dimensionality expansion, random noise injection, and random projection, to provide strong resilience to attacks on the perturbed data and queries. It also preserves multidimensional ranges, which allows existing indexing techniques to be applied to speedup range query processing. The kNN-R algorithm is designed to work with the RASP range query algorithm to process the kNN queries. We have carefully analyzed the attacks on data and queries under a precisely defined threat model and realistic security assumptions. Extensive experiments have been conducted to show the advantages of this approach on efficiency and security.

cs.DB↗