Magnetotransport in atomic-size bismuth contacts

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Atomic-size contacts are crucial for understanding quantum transport phenomena.
• Bismuth (Bi) possesses a long Fermi wavelength, making it suitable for studying quantum effects in constrictions.

Purpose of the Study:

• To investigate low-temperature electrical transport properties of atomic-scale bismuth contacts.
• To explore the transition from diffusive to ballistic and ultra-quantum transport regimes.

Main Methods:

• Fabrication of atomic-size bismuth contacts using the mechanically controlled break-junction technique at low temperatures.
• Measurement of electrical conductance and magneto-transport behavior across a range of contact sizes.
• Analysis of conductance histograms and magnetic field dependence.

Main Results:

• Stable bismuth contacts with conductance values at fractions of the conductance quantum (G0 = 2e^2/h) were observed.
• Two preferred conductance scales were identified: ~0.015 G0 (single-atom Bi contact) and ~0.15 G0.
• Rich magneto-transport behavior, including conductance fluctuations in small contacts and Shubnikov-de Haas oscillations in larger contacts, was detected.
• A transition from diffusive to ballistic and ultra-quantum transport regimes was inferred with decreasing contact size.

Conclusions:

• Atomic-scale bismuth contacts exhibit distinct quantum transport phenomena.
• The observed conductance scales and magneto-transport behavior are consistent with theoretical predictions for quantum transport in nanocontacts.
• Contact size plays a critical role in governing electron transport regimes, from diffusive to ultra-quantum.