Condensed Matter Seminar: Subir Sachdev (Harvard) - Ancilla Layer Model theory of the cuprate phase diagram

Headshot of Subir Sachdev
Mon, March 9, 2026
10:00 am - 11:00 am
1080 Physics Research Building

Condensed Matter Seminar: Subir Sachdev, Harvard University

Ancilla Layer Model theory of the cuprate phase diagram

 

Event Details:

  • Date: March 9, 2026
  • Time: 10:00 - 11:00 AM
  • Location: 1080 Physics Research Building
  • Faculty Host: Mohit Randeria

 

Abstract

The fractionalized Fermi liquid (FL*) features a Fermi surface of electronic quasiparticles enclosing a non-Luttinger volume, along with neutral $S=1/2$ spinon excitations. It has numerous features which make it an attractive description of the pseudogap phase of the cuprates. But it has long been a challenge to develop a systematic theory of FL* in a single-band Hubbard-type model. I will describe a theory employing a bilayer of ancilla qubits which provides a mean-field theory of the FL* phase, along with gauge theories of various confinement transitions out of the FL* phase. I will discuss how these theories can help describe key features of the cuprate phase diagram.

 

Bio

Subir Sachdev is Herchel Smith Professor of Physics at Harvard University. He has been elected to national academies of science in India and the US, and the Royal Society in the U.K. He is a recipient of several awards, including the Dirac Medal from the International Centre for Theoretical Physics, and the Lars Onsager Prize from the American Physical Society.

Sachdev has made extensive contributions to the theory of the diverse varieties of states of quantum matter, and of their behavior near quantum phase transitions.