Symmetry-enforced three-dimension Dirac phononic crystals

March 19, 2020

The discovery of new topological states of matter has become a vital goal in fundamental physics and material science. A three-dimensional (3D) Dirac semimetal (DSM), accommodating many exotic transport properties such as anomalous magnetoresistance and ultrahigh mobility, is an exceptional platform for exploring topological phase transitions and other novel topological quantum states. It is also of fundamental interest to serve as a solid-state realization of a (3+1)-dimensional Dirac vacuum. So far the realized Dirac points always come in pairs and could be eliminated by their merger and pairwise annihilation through the continuous tuning of parameters that preserve the symmetry of the system.

In a new paper published in Light Science & Application, scientists from the Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, China, we report an experimental realization of a 3D phononic crystal that hosts symmetry-enforced Dirac points at the Brillouin zone corners. Markedly different from the existed DSMs, the occurrence of Dirac points is an unavoidable result of the nonsymmorphic space group of the material, which cannot be removed without changing the crystal symmetry. In addition to the Dirac points identified directly by angle-resolved transmission measurements, highly intricate quad-helicoid surface states are unveiled by our surface measurements and associated Fourier spectra. Specifically, the surface states are composed of four gaplessly crossed spiral branches and thus are strikingly different than the double Fermi arc surface states observed recently in electronic and photonic systems.

"This study may open up new manners for controlling sound, such as realizing unusual sound scattering and radiation, considering the conical dispersion and vanishing density of states around the Dirac points. The dispersion around the Dirac point is isotropic, and thus, our macroscopic system serves as a good platform to simulate relativistic Dirac physics." the scientists forecast.
-end-


Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences

Related Physics Articles from Brightsurf:

Helium, a little atom for big physics
Helium is the simplest multi-body atom. Its energy levels can be calculated with extremely high precision only relying on a few fundamental physical constants and the quantum electrodynamics (QED) theory.

Hyperbolic metamaterials exhibit 2T physics
According to Igor Smolyaninov of the University of Maryland, ''One of the more unusual applications of metamaterials was a theoretical proposal to construct a physical system that would exhibit two-time physics behavior on small scales.''

Challenges and opportunities for women in physics
Women in the United States hold fewer than 25% of bachelor's degrees, 20% of doctoral degrees and 19% of faculty positions in physics.

Indeterminist physics for an open world
Classical physics is characterized by the equations describing the world.

Leptons help in tracking new physics
Electrons with 'colleagues' -- other leptons - are one of many products of collisions observed in the LHCb experiment at the Large Hadron Collider.

Has physics ever been deterministic?
Researchers from the Austrian Academy of Sciences, the University of Vienna and the University of Geneva, have proposed a new interpretation of classical physics without real numbers.

Twisted physics
A new study in the journal Nature shows that superconductivity in bilayer graphene can be turned on or off with a small voltage change, increasing its usefulness for electronic devices.

Physics vs. asthma
A research team from the MIPT Center for Molecular Mechanisms of Aging and Age-Related Diseases has collaborated with colleagues from the U.S., Canada, France, and Germany to determine the spatial structure of the CysLT1 receptor.

2D topological physics from shaking a 1D wire
Published in Physical Review X, this new study propose a realistic scheme to observe a 'cold-atomic quantum Hall effect.'

Helping physics teachers who don't know physics
A shortage of high school physics teachers has led to teachers with little-to-no training taking over physics classrooms, reports show.

Read More: Physics News and Physics 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.