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Atomically thin diamond, also called diamane, is a twodimensional carbon allotrope and has attracted considerable scientific interest because of its potential physical properties. However, the successful synthesis of a pristine diamane has up until now not been achieved. We demonstrate the realization of a pristine diamane through diamondization of mechanically exfoliated few-layer graphene via compression. Resistance, optical absorption, and X-ray diffraction measurements reveal that hexagonal diamane (h-diamane) with a bandgap of 2.8 ± 0.3 eV forms by compressing trilayer and thicker graphene to above 20 GPa at room temperature and can be preserved upon decompression to ∼1.0 GPa. Theoretical calculations indicate that a (−2110)-oriented h-diamane is energetically stable and has a lower enthalpy than its few-layer graphene precursor above the transition pressure. Compared to gapless graphene, semiconducting h-diamane offers exciting possibilities for carbon-based electronic devices.

We report the superconductivity enhancement of ZrTe on compression up to 33 GPa. The superconducting transition occurs above 4.1 GPa and the superconducting temperature (T ) increases with pressure in further compression, reaching a maximum of 7.1 K at ~28 GPa. An anomalous change of superconducting temperature is seen in the compression above 21 GPa. No structural phase transition is observed in the whole compression up to 36 GPa, but a subtle change in structural parameter is seen between 17-19 GPa, which seems relevant to the anomalous increase in the superconducting temperature. First-principle calculations reveal that the density of states at the Fermi level increases with pressure, which explains the enhancement of T in ZrTe under compression.

Jahn-Teller distortion commonly exists in Cu-containing complex oxides and remarkably changes the electronic property. However, how it functions to pressure in high-entropy oxides (HEOs) remains unknown. Here we studied pressure engineering on quenching the Jahn-Teller distortion in the (Mg 0.2 Ni 0.2 Co 0.2 Zn 0.2 Cu 0.2 )O HEO and its effect on the electronic structure. Synchrotron X-ray diffraction demonstrate that the local structural distortion of the CuO 6 octahedral sublattice in the rocksalt-type (Mg 0.2 Ni 0.2 Co 0.2 Zn 0.2 Cu 0.2 )O HEO is progressively reduced and the distorted structure evolves into a nearly ideal form with increasing pressure up to 40 GPa. Alternating current impedance and ultraviolet-visible absorption reveal a dramatic resistance drop by more than 3 orders of magnitude and an obvious bandgap decrease of ~0.1 eV, accompanied by the pressure-induced quenching of the Jahn-Teller distortion in the (Mg 0.2 Ni 0.2 Co 0.2 Zn 0.2 Cu 0.2 )O HEO. Our study presents a high-pressure route for tuning the local structural distortion and electronic structure of Cu-containing HEOs for optimizing the materials functionality.