Anomalous density fluctuations in a strange metal

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• High-temperature superconductivity remains a central mystery, particularly the origin of the strange metal phase.
• Understanding the dynamic charge response of copper oxides is crucial for elucidating strange metal properties.

Purpose of the Study:

• To measure the dynamic charge response of cuprates with millielectronvolt resolution.
• To investigate the collective properties and charge dynamics of the strange metal phase.

Main Methods:

• Utilized momentum-resolved inelastic electron scattering.
• Measured the dynamic charge response of optimally doped Bi2.1Sr1.9CaCu2O8+x (T_c = 91 K).
• Examined an overdoped crystal (T_c = 50 K) for comparison.

Main Results:

• Observed a featureless, temperature- and momentum-independent continuum in the 0.1-2 eV energy range.
• The continuum exhibited a power-law form (q^2 at low energy, q^2/ω^2 at high energy).
• An overdoped crystal showed a gap-like feature, deviating from the power law outside the strange-metal regime.

Conclusions:

• The strange metal phase displays a new type of charge dynamics.
• Excitations in the strange metal are highly localized, decoupling space and time axes.
• These findings offer insights into the fundamental nature of anomalous metallic behavior.