Aberrant electronic and structural alterations in pressure tuned perovskite NaOsO3

September 18, 2020

The perovskite NaOsO3 has a complicated, but interesting temperature dependent metal-insulator transition (MIT). A team led by Drs. Raimundas Sereika and Yang Ding from the Center for High Pressure Science and Technology Advanced Research (HPSTAR) showed that the insulating ground state in NaOsO3 can be preserved up to at least 35 GPa with a sluggish MIT reduction from 410 K to a near room temperature and possible transformation to a polar phase. The work published in the npj Quantum Materials.

NaOsO3 perovskite undergoes a metal-insulator transition concomitant with the onset of an antiferromagnetic long-range ordering at a Neel temperature of about 410 K which is accompanied by a magnetic ordering without any lattice distortion.

The team carried out a combined experimental and computational study to understand the effect of external pressure on perovskite NaOsO3. They found hidden hysteretic resistance properties with a transient metallic state near 200 K. Also three electronic character anomalies (at 1.7, 9.0, and 25.5 GPa), and a structural transition to the singular polar phase (at ~ 18 GPa) were discovered.

In terms of the MIT, the pressure-dependent electrical transport measurements indicate that the metallic state extends to the lower temperatures very slowly. The TMIT scales almost linearly upon pressure. At around 32 GPa, the MIT becomes much broader, but can still be identified. Importantly, up to this pressure, NaOsO3 preserves the insulating ground state.

In addition, the warming and cooling curves slightly deviate, forming a narrow thermal hysteresis loop below MIT. The hysteresis is progressively attenuated upon pressure but eventually disappears at about 18 GPa. "The observed hysteresis raises a question if MIT is really the second-order type that was initially assigned," Sereika said.

Further, when the pressure is increased, the Raman results show that NaOsO3 experiences a structural change. The Raman spectra in particular demonstrate the enhancement of the number of phonons and the pressure-induced-splitting of phonon mode above 18 GPa.

"Our pressure-dependent Raman measurements support the fact that the crystal symmetry does not change up to 16 GPa at room temperature and indicates that further pressure increase causes structural transformation to a different symmetry," Ding explained.

"At about 26 GPa, the continuous large-scale reduction in intensity is observed as the pressure increases. Finally, the Raman modes almost vanish at 35 GPa, indicating that sample is approaching a metallic state, that is the MIT," Ding added.

By combining theoretical modeling and experimental data all observed phenomena were explained in detail. A rich electronic and structural phase diagram of NaOsO3 shows the different types of transitions occurring in the system when pressure and temperature are applied: insulator-to-bad metal, bad-metal-to-metal, the anomalous metal island in the bad-metal region, and the subtle non-polar to polar structural transition.

At low temperature the system remains insulating up to a certain critical pressure (~20 GPa in DFT) and then transforms into a bad metal due to the closing of the indirect gap. In this pressure range the valence and conduction bands are still separated by a direct gap. This gap closes at very large pressure, indicating that the evolution of the electronic properties upon pressure share similarities with the temperature-induced band gap closing process.

"The magnetically itinerant Lifshitz-type mechanism with spin-orbit and spin-phonon interactions is responsible for these pressure-induced changes," Ding remarked. "Our findings provide another new playground for the emergence of new states in 5d materials by using high-pressure methods."
-end-
More details: "Aberrant electronic and structural alterations in pressure tuned perovskite NaOsO3", npj Quantum Materials (2020) 5:66.

Center for High Pressure Science & Technology Advanced Research

Related Pressure Articles from Brightsurf:

A pressure sensor at your fingertips
Researchers have developed an ultrathin pressure sensor that can be attached directly to the skin.

High blood pressure treatment linked to less risk for drop in blood pressure upon standing
Treatment to lower blood pressure did not increase and may decrease the risk of extreme drops in blood pressure upon standing from a sitting position.

Changes in blood pressure control over 2 decades among US adults with high blood pressure
National survey data were used to examine how blood pressure control changed overall among U.S. adults with high blood pressure between 1999-2000 and 2017-2018 and by age, race, insurance type and access to health care.

Effect of reducing blood pressure medications on blood pressure control in older adults
Whether the amount of blood pressure medications taken by older adults could be reduced safely and without a significant change in short-term blood pressure control was the objective of this randomized clinical trial that included 534 adults 80 and older.

Brain pressure controls eye pressure, revealing new avenues for glaucoma treatment
Neuroscientists have discovered that eye and brain pressure are physiologically connected.

A question of pressure
The Physikalisch-Technische Bundesanstalt (PTB) has implemented a novel pressure measurement method, as a byproduct of the work on the 'new' kelvin.

Volcanoes under pressure
When will the next eruption take place? Examination of samples from Indonesia's Mount Merapi show that the explosivity of stratovolcanoes rises when mineral-rich gases seal the pores and microcracks in the uppermost layers of stone.

Here's something that will raise your blood pressure
The apelin receptor (APJ) has been presumed to play an important role in the contraction of blood vessels involved in blood pressure regulation.

Under time pressure, people tell us what we want to hear
When asked to answer questions quickly and impulsively, people tend to respond with a socially desirable answer rather than an honest one, a set of experiments shows.

Arm cuff blood pressure measurements may fall short for predicting heart disease risk in some people with resistant high blood pressure
A measurement of central blood pressure in people with difficult-to-treat high blood pressure could help reduce risk of heart disease better than traditional arm cuff readings for some patients, according to preliminary research presented at the American Heart Association's Hypertension 2019 Scientific Sessions.

Read More: Pressure News and Pressure Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.