Pressure‐Induced Superconductivity in HgTe Single‐Crystal Film

Abstract

HgTe film is widely used for quantum Hall well studies and devices, as it has unique properties, like band gap inversion, carrier‐type switch, and topological evolution depending on the film thickness modulation near the so‐called critical thickness (63.5 Å), while its counterpart bulk materials do not hold these nontrivial properties at ambient pressure. Here, much richer transport properties emerging in bulk HgTe crystal through pressure‐tuning are reported. Not only the above‐mentioned abnormal properties can be realized in a 400 nm thick bulk HgTe single crystal, but superconductivity is also discovered in a series of high‐pressure phases. Combining crystal structure, electrical transport, and Hall coefficient measurements, a p‐n carrier type switching is observed in the first high‐pressure cinnabar phase. Superconductivity emerges after the semiconductor‐to‐metal transition at 3.9 GPa and persists up to 54 GPa, crossing four high‐pressure phases with an increased upper critical field. Density functional theory calculations confirm that a surface‐dominated topologic band structure contributes these exotic properties under high pressure. This discovery presents broad and efficient tuning effects by pressure on the lattice structure and electronic modulations compared to the thickness‐dependent critical properties in 2D and 3D topologic insulators and semimetals.

Cation-Exchange-Derived Wurtzite HgTe Nanorods for Sensitive Photodetection in the Short-Wavelength Infrared Range

“…Here, we note that, previously, the WZ phase has never been observed in the bulk form of HgTe. High-pressure studies 31,32 revealed the following sequence of phases for HgTe: ZB (stable up to 1.5 GPa), cinnabar (1.2−8.0 GPa), rock salt (8.0−11.5 GPa), Cmcm phase (12.7−27.1 GPa), and bcc (>27.1 GPa), whereas no WZ was indicated. Additionally, the WZ phase is considered metastable in the case of a HgTe semiconductor.…”

On the Suitable Choice of Metal for HgTe Nanocrystal-Based Photodiode: To Amalgam or Not to Amalgam

“…The film of HgTe coated with Au displays the expected vibrational features for HgTe at 92, 123, and 140 cm –1 attributed to the LA, TO, and LO phonons, respectively. A weaker 2LO phonon mode also appears at around 270 cm –1 . None of these modes are observed in the film with Ag coating, suggesting a strong chemical reorganization of the sample.…”

“…A weaker 2LO phonon mode also appears at around 270 cm −1 . 33 None of these modes are observed in the film with Ag coating, suggesting a strong chemical reorganization of the sample.…”

Vanishing Confinement Regime in Terahertz HgTe Nanocrystals Studied under Extreme Conditions of Temperature and Pressure

“…45 However, the latter effect was the result of the pressure on the quantum confinement through a modification of the effective mass of the electrons. Further exploration of this phase, in particular at an even lower temperature, will be of utmost interest because the latter has been observed to be superconductive around 6 K. 47 In the rock salt phase, the sample becomes strongly absorbent and the spectrum becomes almost saturated over the whole spectral range. We attribute this behavior to the transition toward the metallic phase.…”

“…However, the latter effect was the result of the pressure on the quantum confinement through a modification of the effective mass of the electrons. Further exploration of this phase, in particular at an even lower temperature, will be of utmost interest because the latter has been observed to be superconductive around 6 K …”