Gap-Opening Transition in Dirac Semimetal ZrTe_{5}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• ZrTe5 is a material exhibiting Dirac semimetal properties.
• Understanding quantum phenomena in ZrTe5 is crucial for exploring novel electronic states.

Purpose of the Study:

• To investigate the electronic properties of the Dirac semimetal ZrTe5 using nuclear magnetic resonance (NMR) spectroscopy.
• To probe for evidence of excitonic pairing and charge density waves.

Main Methods:

• ^{125}Te nuclear magnetic resonance (NMR) spectroscopy was employed.
• Experiments were conducted with the NMR magnetic field applied parallel to the b axis.

Main Results:

• A significant drop in spin-lattice relaxation rate at 150 K suggests a gap-opening transition in Dirac carriers, indicative of excitonic pairing.
• A negative shift observed below 50 K points to repopulation of Dirac levels with spin-polarized carriers, consistent with the 3D quantum Hall regime.
• No evidence for a charge density wave was detected, contrary to previous proposals.

Conclusions:

• The study reveals a gap-opening transition and spin polarization in ZrTe5, supporting excitonic pairing.
• The findings challenge existing models by ruling out a charge density wave in the observed 3D quantum Hall regime.